2 CHEMISTRY SCIENCE UNIT-1 - NIMS · PDF fileWorksheet-3.1 Content 3 pH of acids, bases and...

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THERMAL PHYSICS

Learning outcomes - Core

At the end of this unit, students should be able to

Explain, how solids, liquids and gases expand.

Understand the importance and significance of thermal expansion in different

practical situations.

Define specific heat capacity and specific latent heat.

Solve numericals based on specific heat capacity and specific latent heat.

Understand, how heat gets transferred through solids, liquids and gases.

Differentiate between conduction, convection and radiation.

Learn about different methods of heat transfer in different situations in nature

and man made devices.

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1SCIENCE UNIT-1 chemistry

Chemis tryChemis tryUNIT-1 UNIT-1

ACIDS, BASES AND SALTS

SCIENCE UNIT-1CHEMISTRY

SCIENCE UNIT-1 chemistry

Chemis try

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Learning outcomes - Core

At the end of this unit, students should be able to -

Define acids and bases in terms of H+ and OH-

List and explain characteristic properties of acids and bases.

Name several common acids and bases.

Distinguish between acids and bases and demonstrate how to test for them

Identify and describe strong and weak acids and bases.


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Characteristic chemical and

physical properties of acids and

bases.

Strong and weak acids and

bases.

Acids and bases in our daily

routine.

Nature of oxides.

Preparation of salts and their

nature.

Properties of carbon dioxide,

hydrogen and chlorine gases.

Core

Syllabus Coverage

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Extension

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Calculation of pH of a given

solution.

Properties of ammonia, and

oxygen gases.

Identification of the composition

of some salts.

SCIENCE UNIT-1chemistry

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Define acidity and alkalinity in terms of pH

Understand the concept of acids and bases in our daily routine.

Describe the role of antacids and understand neutralization using real life problems.

Identify acidic, basic and neutral oxides.

Explain the preparation of salts and their nature.

Identify carbon dioxide, hydrogen and oxygen gases.

See how acids and bases combine to produce salts

At the end of this unit, students should be able to-

Understand the pH scale as it corresponds to acidic and basic solutions

Calculate the pH of a given solution using log.

Identify NH and Cl gases.3 2

Identify the composition of salts by performing qualitative anion and cation analysis.

Biology/Life Sciences - Cell Biology

Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surrounding, pH of the mouth, tooth decay, acidity in stomach, cure of bee and wasp sting.

Mathematics - Calculation of pH of a given solution(extension)

Environment - pH of the soil, acid rains due to environmental pollution,

Music- A rap song on pH and another on properties of acids and bases

Home Science- The salts in the kitchen and usage of the salts for various house-hold activities.

Learning outcomes - Extension

Cross curricular links

70


Lesson Template

Teacher's Activity Student's ActivitySteps to be

followed

Teacher may start by asking few

brain storming questions related

to daily life experiences.

We have studied about

nutrition in animals, recall

what is secreted by the inner

lining of the stomach to help in

the process of digestion?

Have you ever suffered from

a c i d i t y i n s t o m a c h /

indigestion?

How do we cure it? Do you

remember any advertisement

or an occasion at home where

acidity in stomach and its cure

were discussed?

Have you ever used baking

soda in the kitchen?

Have you eaten salads with

vinegar dressings?

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•

Students try to think and

answer by recalling the

concepts learnt in biology.

Students try to think and

a n s w e r f r o m t h e i r

experiences.

Warming up

Activity

71

Teacher asks the students as to

what they understand by the

terms acids and bases?

Students have an idea about

these terms from their lower

classes, they discuss in class

and also give some examples

that they know.

Pre Content

Acids and Bases

SCIENCE UNIT-1chemistry72

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The teacher lists the properties of

acids and bases as told by the

students on the board

Teacher takes the students through

the experience of finding the acidic

or bas ic nature of var ious

substances which are of daily use for

example- shampoo, soap, water, tea,

fruits, etc.

Teacher may involve the students in

the pre-lesson activity of bringing

various samples from home to be

tested.

Activities: 1A, 1B, 1C, 1D.

Following video may be shown to the

students so that they have fun while

learning

http://www.youtube.com/watch?v=

zTLiJE-j1-I&feature=related

Red Cabbage pH Indicator

http://www.youtube.com/watch?v=

6fc8KBz_I9s&feature=related

ACTIVITY-2

Learning objectives:

The students will be able to-

define, dissociation, electrolyte, non-electrolyte, pH.

predict if a compound is an electrolyte or a non-electrolyte.

explain how an electrolytic solution c o m p l e t e s t h e c i r c u i t i n a conductivity apparatus so that the light bulb glows.

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The students will be able

to-

Describe acids and

bases in terms of H+

and OH-

Distinguish between

acids and bases on

the basis of their

behaviour towards

litmus indicator

C a t e g o r i s e

substances as acidic

or alkaline?

Worksheet:1.1

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Take any popular soft

drink which promises to

replenish your body's

electrolytes when you

drink it. Use the internet

t o r e s e a r c h w h i c h

i n g r e d i e n t ( s ) a r e

contained that make this

drink an electrolytic

solution. Also research

how the body uses

Concept

Development

Content 1

Acid And Base-

experimentation

and development

of concept further

Content 2

Dissociation of

acids and bases,

Electrical

conductivity

SCIENCE UNIT-1 chemistry73

• Distinguish between strong and

weak acids and bases in terms of the

extent of dissociation, reaction with

water and electrical conductivity.

ACTIVITY-3


Students Will be able to-


Understand role of pH in day to day life.

Following video links on youtube may be shown in the class to sum up the concept.

http://www.youtube.com/watch?v=fHd7wRkJNgI&feature=related

http://www.youtube.com/watch?v=M8tTELZD5Ek&feature=related

The pH scaleVideo:


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electrolytes and why

t h e y n e e d t o b e

r e p l e n i s h e d a f t e r

exercise.

Worksheet-2.1

Students bring various

t h i n g s l i k e s o a p ,

detergent, moisturizing

lotion, spices from the

kitchen etc to test their

pH.

Worksheet-3.1

Content 3

pH of acids, bases

and salts

Activity-4



Observe and study the reaction of acids with a metal

Compare the reactivity of different metals with the same acid.

Compare the reactivity of different acid with same metal.

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Students perform the

activity and follow up

witgh the worksheet.

Worksheet 4.1

Content 4

Reaction of acids

with metals


Activity-5



Appreciate that metals develop an

oxide coating over a period on

exposure to air

Observe and study the reaction of

acids with a metal oxide.

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ACTIVITY-6



Observe and study the reaction of acids with a carbonate.

Observe and study the effect of carbon dioxide gas on lime water.

Teacher may use the following site in the class to bring virtual kitchen experience or guide the students to perform activities at home in the real kitchen.

http://pbskids.org/zoom/games/kitchenchemistry/

Students perform collect

dull coins and articles

from home and bring

back the shine using

vinegar. They may be

involved in hypothesis -

whether acids or bases

should be used to clean

the metal surface.

Worksheet-5.1

Extension activity:

Students design a soda

acid fire extinguisher,

b a s e d o n r e a c t i o n

between sulphuric acid

and sodium hydrogen

carbonate students

Recognise the release

a n d p r o d u c t i o n o f

hydrogen gas.

Worksheet-6.1

Content 5

Reaction of acids

with metal oxides

Content 6

Reaction of acids

with carbonate

and bicarbonates

of metals.

Preparation and

Properties of

carbon dioxide

gas.

ACTIVITY-7



Define neutralization

Identify the products of a chemical reaction between an acid and a base.

Write the word equations for the observed chemical reaction

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Extension activity:

Students design a soda

acid fire extinguisher,

b a s e d o n r e a c t i o n

between sulphuric acid

and sodium hydrogen

carbonate students

Content 7

Neutralization

reaction and

balancing of

reactions


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Write symbols and formulae for the reactants and products

Balance the chemical equation for the observed reaction.

Activity-8

Learning Objectives:

The students will be able to:

Recall that an acid reacts with a base to produce salt and water.

Recognise the acid and base that would combine to give the given salt.

Correlate the acidic, basic or neutral nature of the salt to the strength of the acid and base which may be used to obtain the salt

Appreciate that all salts are not neutral.

Conceptualise the formation and nature of a salt.

Salts http://www.youtube.com/watch?v=LHRek-ROQjE

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Recognise the release

and product ion o f

hydrogen gas.

Worksheet-6.1

Content 8

Salts

Teacher may start with some commonly used salts in the kitchen and hold a small discussion in the class showing the samples and some simple reactions may follow.

Activity-9

Students strengthen the

concept by working on

the worksheet.

Worksheet-9.1

Content 9

Some important

salts


ACTIVITY 10

The process of identifying unknown

cations or anions in a solution is called

Anion and Cation analysis

Resource:

Resource:

http://www.docbrown.info/ks3chemistry/ks3chemistry.htm

Resource:

http://www.docbrown.info/page04/Y11revQs/acidreactionequationsFH.htm

Students will perform

qualitative analysis of

salts to identify the

composition of given

salt.

Revision worksheets-

1,2,3,4

Content 10

Qualitative

Analysis of Anions

and cations

5. Post Content

Activity

Revision

Teacher initiates an investigation by asking a guiding question.

Chemistry Investigation

Guiding Question: "Which is the most effective antacid?"

Students formulate hypothesis, decide on the variables and reach conclusions to be shared in groups.

Peer evaluat ion by taking feedbacks from other groups.

6. Extension


Why Study about Acids, Bases and Salts?

Teacher may ask following questions to relate the topic to their day today life so that they

realize the need to study about Acids, Bases and Salts.

We have studied about nutrition in animals, recall what is secreted by the inner

lining of the stomach to help in the process of digestion? Was it mucous,

hydrochloric acid and digestive juices?

Have we ever suffered from acidity in stomach/ indigestion?

How do we cure it? Do we remember any advertisement or an occasion at home

where acidity in stomach and its cure were discussed?

We have carried out activities of tasting food and categorising them as sour,

bitter, sweet or salty in lower classes. How are these chemically same or

different?

What makes the cake fluffy or the pakoras crispy?

Why are farmers advised to get their soil tested before selecting and putting

fertilisers?

Why are we coaxed to brush and rinse our mouth after eating?

Why people rub an iron key or baking soda as a home remedy for relief from

itching caused due to bee or red ant sting?

Can you think of some more examples from everyday life?

To know answers to these we'll have to study about acids, bases and salts. We come in

contact with them when cooking, cleaning and eating.

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Warm up Activity



ACTIVITY-1

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ACID OR ALKALI? ACIDIC OR ALKALINE?


Distinguish between acids and bases on the basis of their behaviour towards

litmus indicator

Distinguish between acids and bases on the basis of their behaviour towards

home made indicators-turmeric, red cabbage etc.

Describe acids and bases in terms of H+ and OH-

According to earlier views,

Acids produce solutions that:

taste sour.

react with metals to liberate hydrogen gas.

turn blue litmus red.


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Acid Household Source Base Household Source

conduct electricity.

are corrosive. (acid rain)

loose the above properties when reacted with a base.

Bases produce solutions that:

taste bitter.

turn red litmus blue.

conduct electricity.

feel slippery.

are corrosive (basic solution in glass container)

lose the above properties when reacted with an acid.

citric acid oranges, grapefruits sodium hydroxide oven cleaner

(caustic soda)

tartaric acid Grapes magnesium milk of magnesia

hydroxide

ascorbic acid Vitamin C

acetic acid Vinegar

methanoic acid stingers of some ants

butanoic acid rancid butter

oxalic acid Tomatoes

stearic acid animal fat

According to one of the modern theories of acids and bases (Arrhenius concept), An acid is a

substance which give hydrogen ions in aqueous solution for e.g. HCl (Hydrochloric acid),

H SO (Sulphuric acid) etc. Substances like C H OH (ethyl alcohol), C H 2O (glucose) etc. 2 4 2 5 6 1 6

though contain hydrogen are not acidic as they do not produce hydrogen ion when

dissolved in water.

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Base is a substance which give hydroxyl ions in aqueous solution For e.g. NaOH (sodium

hydroxide), NH OH (ammonium hydroxide) etc are bases. Substances like C H OH (ethyl 4 2 5

alcohol) contains -OH group but it does not ionize in the aqueous solution to give OH- ions.

Hence, it is not a base.

NOTE- The bases which are soluble in water are called alkalies. Thus all alkalies are bases

but all bases are not alkalies.


TESTS TO DISTINGUISH BETWEEN ACIDS AND BASES

Indicators are chemicals that indicate whether a substance is an acid or a base We use acid-

base indicators to distinguish between acids and bases. Depending upon the property of

the indicator we have the following two types of acid base indicators:

A. Indicators showing different colours in acidic and basic medium

Litmus solution- Litmus solution is a purple coloured dye extracted from lichen

plant. It is the most commonly used natural indicator. Two types of litmus

solutions are used called blue litmus solution and red litmus solution. An acid

turns blue litmus solution to red colour and a base turns red litmus solution to

blue colour.

If the blue litmus paper turns red or the red litmus paper is unaffected then the

substance is acidic.

If the red litmus paper turns blue or the blue litmus paper is unaffected then the

substance is alkaline.

If neither red nor the blue paper changes colour, the substance is neutral.

Note- Turmeric is a natural indicator which is yellow in colour. It becomes reddish

brown when soap, which is basic in nature is scrubbed on it.

Synthetic Indicators- The two most commonly used synthetic acid-base

indicators are phenolphthalein and methyl orange. Their colours in acidic and

basic solutions are-

Phenolphthalein Colourless Pink

Methyl orange Pink Yellow

B. Indicators giving different odours in acidic and basic medium (Olfactory

indicators)-There are some substances which give one type of odour in acidic

medium and a different odour in the basic medium. Vanilla essence, clove oil and

onion odoured cloth strip are some of the olfactory indicators used.

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Indicators Colour in acidic solution Colour in basic solution

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Type of Activity: Warm up

Activity-1A

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Aim:

Materials Required:

To test a variety of substances to see if they are acidic or alkaline using litmus paper

as an indicator.

Red and blue litmus paper (3 strips of each)

Access to small amounts of common everyday substances such as:

fizzy drinks

tap water

distilled water

toothpaste

shampoo

soap

vinegar

lemon juice


Technical notes

Procedure:

Observations:

1. Provide small amounts of the samples on watch glasses. The watch glasses can be

placed on a white tile marked with the name of the substance - use a waterproof

marker.

2. The samples can be arranged around the room so that the students visit each in turn. If

any solid sample is used, moisten it with a little distilled water.

1. Tear each piece of litmus paper into 3 smaller pieces so that you can test at least 9

substances.

2. Take one small piece of red litmus paper. Dip it into one of the substances to be tested.

Repeat with a small piece of the blue litmus paper.

3. Record all observations. Then dispose of the pieces of litmus paper in the waste bin.

Fizzy drinks

Tap water

Distilled water

Toothpaste

Shampoo

Soap

Vinegar

Lemon juice

Name of substance Effect on blue Effect on red Nature

litmus paper litmus paper (Acidic/Basic/

Neutral)

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Extension Activities:

Activity-1B

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The juice of the red cabbage leaf is a naturally occurring acid base indicator. Use the

internet to research if there are any other naturally occurring pH indicators. If so what do

they share in common with the red cabbage? What are the differences? Then collect

samples of various cleaning solutions, cosmetic solutions, cough syrups, and beverages

that are available in your home. Based on their functions, predict whether these solutions

are acidic, basic, or neutral. Then design an experiment to verify your predictions. Be sure

to include which indicator you plan to use and why you picked it.

Indian curries contain turmeric (haldi). The curcuma present in turmeric reacts with base

to form a red coloured substance whereas it does not change colour in acidic or neutral

solution. Now can you tell without tasting the nature of soap and lemon juice respectively?

Yes your guess is right- soap is a basic in nature whereas lemon juice is either acidic or

neutral.

To test a variety of substances to see if they are acidic or alkaline using turmeric as an

indicator.

Beaker

Test tubes

Dropper


Lemon juice

Orange Juice

Vinegar

Curd

Tamarind

Juice

Turmeric as indicator

Aim:

Materials Required:


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S.No. Substance Effect on Turmeric Solution

Soap solution

Baking soda

Table Salt Solution

Sugar Solution

Tap Water

Mix half a tea spoon full of turmeric in water and filter the yellow solution in a

beaker

Collect the following substances- lemon juice, orange juice, vinegar, curd,

tamarind juice, soap solution and baking soda

Fill the test tubes with one third of these solutions respectively.

Add few drops of turmeric solution with the help of a dropper and observe the

change in colour of turmeric solution.

1 Lemon Juice

2 Orange Juice

3 Vinegar

4 Curd

5 Tamarind Juice

6 Soap Solution

7 Baking Soda

8 Table Salt Solution

9 Sugar Solution

10 Tap Water

Procedure:

Observations:

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Activity-1C

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Aim:

Materials Required:

Procedure:

To test a variety of substances to see if they are acidic or alkaline using turmeric as an

indicator.

China rose flowers

Hot water

Test tubes


Lemon juice

Orange Juice

Vinegar

Curd

Tamarind

Juice

Soap solution

Baking soda

Table Salt Solution

Sugar Solution

Tap Water

Pluck few china rose flowers, remove their petals and put these in boiling water.

Let them soak for in hot water for ten minutes.

Filter the solution. Your china rose extract is ready.

Note the colour of the extract.


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S.No. Substance Effect on China Rose Extract

Activity-1D

Keep 2mL extract in one test tube as control (do not add anything to it) so as to

match and track the colour change.

Test the rest of the solutions collected in activity-1B with the extract and record

your observations in a table.

1 Lemon Juice

2 Orange Juice

3 Vinegar

4 Curd

5 Tamarind Juice

6 Soap Solution

7 Baking Soda

8 Table Salt Solution

9 Sugar Solution

10 Tap Water

Phenolphthalein is a synthetic indicator. It forms a colourless solution when dissolved in

water. Colour of phenolphthalein does not change in acidic or neutral medium. When a

drop of phenolphthalein is added to a base it imparts pink colour. So phenolphthalein is a

base indicator.

Test the solutions collected in activity 1 with phenolphthalein indicator and record your

observations.

Observations:

Phenolphthalein as Indicator

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Testing with Red Cabbage Juice

Prepare red cabbage or black carrot juice. (In northern regions of India people prepare a

sour refreshing drink called 'kanji' using black carrot, rye seeds, water, salt to taste and

chilli powder) and test various substances at home to classify them as acidic, basic or

neutral. The red cabbage juice turns red with acid, and green to blue with base. The colours

in base change from one shade to another in a few minutes, so you should note your

observations fast

Colour: acidic solution'Dark Magenta or Red

Add Soap Solution ' Turns bluish green

Following video may be shown to the students so that they have fun while learning

http://www.youtube.com/watch?v=zTLiJE-j1-I&feature=related

1. The Invisible Ink Demonstration can be done at the end of this lesson as an evaluation

of the students' learnings during the lab activity. Students will be required to explain

the invisible ink demo and this will require that they apply their knowledge of

indicators acids and bases.

(Dip cotton swab into the vinegar & use it to write your secret message on the

paper.Allow about 1-2 min for the message to dry completely.Read the "invisible ink"

message by misting it lightly with the spray bottle filled with red cabbage juiceor any

indicator)

2. Are most house cleaning substances acids or bases? Are most food product acids or

bases?

3. Disappearing "blood" squirt guns and disappearing ink pens are available in toy

stores. Both use indicators and acid/base chemistry. What indicators and acidic or

basic solutions would give you such effects?

4. In basic medium colour of phenolphthalein is:

(a) Yellow (b) Orange

(c) Pink (d) Colourless

WORKSHEET 1.1


5. The acid present in sour milk is :

(a) Citric acid (b) Lactic acid

(c) Oxalic acid (d) Tartaric acid

6. Name the acid present in lemon juice and sting of bees.


define dissociation, electrolyte, non-electrolyte, pH, neutralization.

predict if a compound is an electrolyte or a non-electrolyte.

explain how an electrolytic solution completes the circuit in a conductivity

apparatus so that the light bulb glows.

Distinguish between strong and weak acids and bases in terms of the extent of

dissociation, reaction with water and electrical conductivity.

It is observed that in water, acid molecules break up or dissociate into ions.

+ -HCl(aq) Ý H (aq) + Cl (aq)

Hydrochloric acid, thus, contains H+ ions.

Solutions of all acids in water contain H+ ions.

This is proved by the following experiment:

Take sodium chloride in a dry test tube and add some sulphuric acid into the test tube.The

following reaction takes place-

NaCl + H SO Ý NaHSO + HCl2 4 4

Sodium chloride Sulphuric acid Sodium bisulphate Hydrochloric acid

Bring a dry blue litmus paper on the mouth of the test tube. It is observed that the litmus

paper does not turn red. Now, bring a wet blue litmus paper on the mouth of the test tube. It

ACTIVITY-2

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Dissociation and Electrolyte

89


is observed that it turns red. The result clearly show that HCI acts as an acid only in the

presence of water as moist litmus paper has water in which HCl gas is dissolved. It is only +after coming in contact with water that HCl dissociates into ions, i.e., hydrogen ions (H )

-and chloride ions (Cl )

+ -HCl (g) + Water Ý H (aq) + Cl (aq)

Bases generate hydroxide (OH-) ions when dissolved in water. Bases which are soluble in

water are called alkalis.

+ -KOH(aq) Ý K (aq) + OH (aq)

Compounds that dissolve in water and dissociate into ions can conduct electricity and are

called electrolytes. Electrically neutral particles that are soluble in water, such as sugar, do

not split up into ions and therefore, they do not conduct electricity ; hence are referred to as

non-electrolytes. (This theory was originally proposed by Svante Arrhenius in 1887.)

Solutions of acids or bases contain ions and are therefore electrolytes. A strong acid/base is

an acid/base that is almost completely dissociated into ions in its aqueous solution. Such

an acid/ base shows high conductivity

A weak acid/base is an acid/base that is weakly dissociated ie. partially dissociated in its

aqueous solution. Such an acid/ base shows low conductivity

Hydrochloric acid : HCl Acetic acid : CH COOH3

Nitric acid : HNO Phosphoric acid : H PO3 3 4

Sulphuric acid : H SO Boric acid : H BO2 4 3 3

Hydrobromic acid : HBr Carbonic acid :H CO2 3

Sodium hydroxide : NaOH Magnesium hydroxide :Mg(OH)2

Potassium hydroxide :KOH Ammonium hydroxide :NH OH4

Strong acids Weak acids

Strong bases Weak bases


NOTE: Although water is not a strong conductor, tap water contains many charged

particles, (eg: magnesium and calcium ions) hence it is dangerous to use electrical

appliances in wet areas.

Using a conductivity apparatus, ask students to explain how they might complete the

circuit so that the light bulb will glow. Are there any materials that they can think of that

can conduct electricity? (metals, water )

Two nails

Cork

Beakers

Source of electricity (6 Volt battery)

appropriate volumes of the following solutions:

1.0 M HCl

1.0 M NaOH

distilled water

solution of sugar and water

vinegar

1. Fix two nails on a cork and placethe cork in a beaker.

2. Connect the nails to the two terminals of 6 volt battery through a bulb and switch.

3. Pour some HCl in the beaker and switch on the current

4. Observe what happens. Does the bulb glow.

5. Repeat the experiment separately with NaOH, distilled water, sugar solution and

vinegar.

Type of activity: Content based

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Materials Required:

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Procedure:

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6. Record observations.

HCl

NaOH

Distlled Water

Sugar solution

Vinegar

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

Observations:

Conclusion:

Solution Intensity of light bulb Conducts Electricity?

(very bright, bright, dim) (yes / no)


Extension activity:

Worksheet-2.1

ACTIVITY-3

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Take any popular soft drink which promises to replenish your body's electrolytes when

you drink it. Use the internet to research which ingredient(s) are contained that make this

drink an electrolytic solution. Also research how the body uses electrolytes and why they

need to be replenished after exercise.

1. Why does the light bulb glow more brightly when the electrodes are immersed in

solutions of HCl and NaOH then in vinegar?

2. Why is it dangerous to use electrical appliances in wet areas? ie: using a hairdryer

while sitting in the bathtub!

3. Why the light bulb glowed when the electrodes were immersed in solutions HCl,

NaOH and vinegar but not in sugar solution and distilled water.

4. Why does NaCl (aq) conduct electricity, but NaCl (s) does not?

5. List at least three household products that would be considered electrolytes.



Understand role of pH in day to day life.

You can say how acidic or alkaline a solution is using a scale of numbers called the pH scale.

The pH of a solution is defined as the negative logarithm of hydrogen ion concentration in

moles per litre.

+pH = -log [H ]


EXPRESSING ACIDITY OR ALKALINITY OF A SOLUTION IN TERMS OF pH

93


-1For example, if a solution has H+ ion concentration =0.1 M ie. 10 moles per litre, its -3pH =1 and if pH of a solution is 3 then concentration of H+ ions is 10 mol per litre.The

values of pH normally lie between 0 and 14.

+It is found that for any aqueous solution (neutral, acidic or basic), the product of H - -14ion concentration and OH ion concentration is always constant and equal to 10 at

25°C.This is called ionic product of water(Kw)

+ -Kw= [H ] [OH ]

= 10-14

+ -Thus for a solution if H concentration is known, OH ion concentration is fixed

(because their product is always constant).Hence we express the acidic, basic or +neutral character of any solution by expressing its H ion concentration in terms of pH

where p stands for potenz ie power.

+ -For neutral solutions : [H ] = [OH ] , pH = 7

+ -For acidic solutions : [H ] > [OH ] , pH < 7

+ -For basic solutions : [H ] < [OH ] , pH > 7

pH |------|------|-----|-----|------|-----|-----|-----|------|------|-----|------|------|------|

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

+[H ] |-----|------|-----|------|-----|-----|-----|-----|------|------|-----|------|------|------|

0 -1 - 2 - 3 - 4 -5 - 6 - 7 - 8 - 9 -10 -11 -12 -13 -14(mol/L) 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

pH between 0 and 2 -Strongly acidic

pH between 2 and 4 -Moderately acidic

pH between 4 and 6 -Weakly acidic

pH 7 -Neutral

pH between 7and 10 -Weakly basic

pH between 10and 12 -Moderately basic

pH between 12and 14 -Strongly basic


pH of any solution can be found by using universal indicator. This is a mixture of dyes

and can be used as solution or paper strip. Colour change in the indicator is seen with

pH.

1. Human blood, tears and saliva have pH range of 7.0 to 7.8, If pH falls below 7 or rises

above 7.8 survival of living organisms becomes difficult.

2. Human skin has a slightly acidic pH. This is necessary to keep away from attack by

microorganisms.

3. Plants have a healthy growth if pH of the soil is such that it is neither alkaline nor

highly acidic.

4. Hydrochloric acid produced in the stomach helps in digestion. However if excess of

acid is produced due to spicy food, it causes indigestion and we have to take 'antacid'

like milk of magnesia (magnesium hydroxide solution) etc.

5. Acid is produced in the mouth due to degradation of sugar and left out particles It is

partially neutralized by the saliva. However, if excess acid is produced due to sweets,

it causes tooth decay.

6. Animals and plants have self defence through chemical warfare. The sting by honey

bee or yellow ant or leaves of nettle plant injects methanoic acid into our body which

causes pain.

7. The tarnished surface of a copper vessel due to copper oxide (which is basic) layer can

be cleaned by rubbing with lemon (which is acidic).

Following video links on youtube may be shown in the class to sum up the concept.

http://www.youtube.com/watch?v=fHd7wRkJNgI&feature=related


ROLE OF pH IN EVERYDAY LIFE


Work Sheet 3.1

ACTIVITY-4

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1. Give reasons for the following:

a. Toothpastes are alkaline in nature

b. We apply solution of mild base on bee or ant sting

c. We rub lemon on tarnished copper vessels.

2. Seven solutions A, B,C, D,E, F and G have pH 1,2,7,9,11,13 and 14 respectively.

a. Identify which of them is strongly acidic.

b. Identify which of them is neutral.

c. Identify which of them is weakly basic.

d. Identify which of them is strongly basic.

e. Which of them will turn phenolphthalein pink?

f. Which of them will turn methyl orange pink?


Observe and study the reaction of acids with a metal

Compare the reactivity of different metals with the same acid.

Compare the reactivity of different acid with same metal.

The only metals that react with acids are those that are more reactive than hydrogen.The

metals give up their electrons to H+ ions will react with acid

The result of the reaction are metal salts of the acid and evolution of bubbles of hydrogen

gas through the solution.


REACTION OF ACIDS WITH METALS


Acid + Metal ÝSalt + Hydrogen gas

Zn (s) + 2H SO (aq) Ý Zn SO (aq) + H (g)2 4 4 2

Zinc dil Sulphuric acid acid Zinc sulphate Hydrogen

Mg (s) + 2H SO (aq) ÝMgSO (aq) + H (g)2 4 4 2

Magnesium dil Sulphuric acid Magnesium sulphate Hydrogen

Al (s) + 3HCl(aq) ÝAlCl (aq) + H (g)3 2

Aluminium dil Hydrochloric acid Aluminium chloride Hydrogen

Cu (s) + 2H SO (aq) Ý No reaction2 4

Copper dil Sulphuric acid

2. Some bases like sodium hydroxide and potassium hydroxide react with active metals

like zinc and aluminium to liberate hydrogen gas along with the formation of a salt.

2NaOH + Zn ÝNa2ZnO2 + H2Sodium hydroxide Zinc Sodium zinczte Hydrogen

2NaOH + 2Al + 2H2O Ý2NaAlO2 + 3H2Sodium hydroxide Aluminium Sodium aluminate Hydrogen

To test the reactivity of metals with an acid and compare their reactivity.

Part -I

2 Boiling test tubes with cork containing a dropping funnel and delivery tube

Clamp stand

Dilute sulphuric acid

Dilute NaOH

Granulated zinc

Soap solution

A candle.

Type of Activity: Content based

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Aim:

Materials required:

97


Part-II

Four boiling test tubes with cork containing a dropping funnel and delivery tube

Four clamp stand

Four empty syringes

Dilute sulphuric acid (1 M)

Zinc granules

Magnesium ribbon

Copper turnings

Aluminium strips

Part-III

Boiling test tubes with cork containing a dropping funnel and delivery tube

Clamp stand

Dilute sulphuric acid

Acetic acid

Granulated zinc

Part-I

1. Take one or two zinc granules in two test tube and close the test tubes with the cork

containing a dropping funnel and delivery tube.

2. Clamp it to the clamp stand.

3. Pour about 3 mL of dilute H SO in one of the test tube and NaOH in the other test tube 2 4

through the thistle funnel. (Take care that end of the thistle funnel is dipped in dilute

H SO solution.)2 4

4. Observe the reactions taking place.

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Procedure:


5. Pass the gas being evolved through the soap solution.

6. Observe what happens to the soap solution. Record the in the observation table.

4. Bring a lighted candle near a gas filled bubble. Record the observation.

Part-II

1. Take zinc ,magnesium , aluminium and copper in four different test tubes. close the

test tubes with the cork containing a dropping funnel and delivery tube.


3. Connect the delivery tube to the mouth of the syringe.

4. Pour about 3 mL of dilute H SO in the test tube through the thistle funnel. (Take care 2 4

that end of the thistle funnel is dipped in dilute H SO solution.) 2 4

5. Measure the distance travelled by the piston of syringe after 5 minutes and record

your observations.

6. Based on above observation compare the relative reactivity of metals taken.

99


Part-III

1. Take zinc granules in two different test tubes. close the test tubes with the cork



3. Connect the delivery tube to the mouth of the syringe.

4. Pour about 3 mL of dilute H SO in one test tube and 3mL of acetic acid in the other test 2 4

tube through the thistle funnel. (Take care that end of the thistle funnel is dipped in

dilute H SO solution.) 2 4

5. Measure the distance travelled by the piston of syringe after 5 minutes and record

your observations.

6. Based on above observation compare the relative strength of the two acids taken.

Part-I-

Reaction of an acid with a metal

1. Effect on soap solution:

_________________________________________________________________________

_________________________________________________________________________

2. Effect on the burning candle:

_________________________________________________________________________

_________________________________________________________________________

Reaction of a base with a metal

1. Effect on soap solution:

_________________________________________________________________________

_________________________________________________________________________

Observations:


2. Effect on the burning candle:

_________________________________________________________________________

_________________________________________________________________________

Part-II- Reaction of an acid with different metals`

Zinc

Magnesium

Alumnium

Copper

Part-III-Reaction of zinc metal with two different acids

Dilute H SO2 4

Acetic acid

Part-I

1. _________________________________________________________________________

_________________________________________________________________________

2. _________________________________________________________________________

_________________________________________________________________________

Metal Rate of Reaction Gas Produced Distance of piston

(Fast / Moderate / (yes/no) from the mouth

Slow / No Reaction)

Acid Rate of Reaction Gas Produced Distance of piston

(Fast / Moderate / (yes/no) from the mouth

Slow / No Reaction)

Conclusion


Part-II

_________________________________________________________________________

_________________________________________________________________________

Part-III

_________________________________________________________________________

_________________________________________________________________________

1. Acids react with metals to form ____________ and _____________

2. Complete the following reactions:

a. Mg + HCl Ý

b. Ca + HNO Ý3

c. Cu + H PO Ý3 4

3. Classify the type of chemical reaction that occurred when the zinc reacted with an

acid.

4. Why did some of the reactions happen at a faster rate than others (*Hint* compare

each acid used, what is different about the acids that were involved in the faster

reactions?)

5. Explain why it is a hazard to store acids in some metal containers, and not others.

6. When sugar is placed in water, it disappears and is said to have dissolved. When

magnesium metal is placed in a solution of hydrochloric acid, it also disappears.

Explain why the magnesium did not dissolve.

7. An advertisement for a trivia game features the following question "Do pearls melt in

vinegar?" the "correct" answer given is "yes." Write a letter to the trivia company

explaining why this is not the case. Use the internet to research the chemical

composition of a pearl. Include a simplified chemical reaction demonstrating what is

really happening with the pearl and vinegar.

WORKSHEET-4.1


ACTIVITY-5

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Learning objective

Reaction of Acids with Metal oxides

Aim:

Materials required:


Appreciate that metals develop an oxide coating over a period on exposure to air

Observe and study the reaction of acids with a metal oxide.

Acids react with certain metals oxides to give metal salt and water.

Most of these oxides are of electropositive metals. Some of the oxides are amphoteric in

nature.

Na O + 2HCl Ý2NaCl + H O2 2

Mgo + 2HCl ÝMgCl + H O2 2

Al O + 6HCl Ý2AlCl + 3H O2 3 3 2

Certain metals, like copper metal, develop a greenish coating of copper oxide, on reaction

with air. Acids, like acetic acids, react with the oxide to effectively remove the coating.

Salts serve as a catalyst, essentially speeding up the chemical reaction. If you'd like to see

what the difference would be, this is easy to do.

To detect and study the reaction of acid with metal oxide

10 dull copper coins

100 mL vinegar

1 teaspoon salt (NaCl)

water

measuring spoons

paper towel

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Procedure

Observation:

Conclusion:

1. In a beaker, marked A, take salt and 50ml vinegar.

2. Stir until the salt dissolves.

3. Dip 5 coins into the solution and hold it there for 10-20 seconds. Remove the coins and

observe for any change.

4. Pour 50ml vinegar only in another beaker, marked B.

5. Dip 5 coins into the vinegar and hold it there. Measure the time it takes for the coins to

lose the clouded appearance. Check every 60 seconds.

6. Drop the rest of the coins into beaker A. Observe the duration of cleaning action.

7. Take out the coins from the beaker with a spoon and rinse it with water.

8. Set it on a paper towel to dry.

1. Observe the coins for regaining the shiny appearance, on the action of vinegarof the

side of the test tube on pouring acid:

_________________________________________________________________________

2. Which beaker showed the cleaning action faster beaker A or beaker B

_________________________________________________________________________

_________________________________________________________________________

_________________________________________________________________________

1. Acids react with metal oxides to form ____________ and ____________ .


a. HCl + CuO Ý

WORKSHEET-5.1


b. HCl + MgO Ý

c. HNO3 + Na2O Ý

3. Explain, with the help of a chemical equation, the role of salt in this activity.

4. Why don't we use a base or soap to clean the metal surface?


Observe and study the reaction of acids with a carbonate.

Observe and study the effect of carbon dioxide gas on lime water.

1. Acids react with metal carbonates and bicarbonates to give out carbon dioxide with

effervescence and forming the corresponding salt and water.

Metal carbonates/Metal hydrogencarbonate + Acid Ý Salt + Carbon dioxide + Water

Na CO (s) + 2HCl (aq) Ý2NaCl(aq) + H O(l) + CO (g)2 3 2 2

Sodium carbonate Hydrochloric acid Sodium chloride Water Carbon dioxide

NaHCO (s) + HCl(aq) ÝNaCl(aq) + H O(l) + CO (g)3 2 2

Sodium bicarbonate Hydrochloric acid Sodium chloride Water Carbon dioxide

On passing the carbon dioxide gas evolved through lime water,lime water turns

milky due to the formation of insoluble calcium carbonate.

Ca(OH) (aq) + CO (g) ÝCaCO (s) + H O(l)2 2 3 2

Lime water Carbon dioxide Insoluble calcium Water

carbonate

On passing excess of carbon dioxide the lime water turns transparent due to

formation of soluble calcium bicarbonate.

Ca(OH) (aq) + CO (g) ÝCa(HCO ) (aq)2 2 3 2

Lime water Carbon dioxide Soluble calcium bicarbonate

ACTIVITY-6

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REACTION OF ACIDS WITH CARBONATES

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Aim:

Materials required:

Procedure:

To test the reactivity of acids with a carbonate.

Boiling test tubes with cork containing a dropping funnel and delivery tube

Clamp stand

Dilute hydrochloric acid

Solid sodium carbonate

Lime water

1. Take solid sodium carbonate in the test tube and close the test tube with the cork



3. Pour about 3 mL of dilute HCl in the test tube through the thistle funnel. (Take care

that end of the thistle funnel is dipped in dilute HCl solution.)

4. Observe the reaction taking place. Record the observation.

5. Pass the gas evolved through the lime water taken in a test tube.

6. Observe what happens to the lime water. Record the observation.

7. Pass the gas evolved in the lime water for longer time and observe what happens?

Record the observation.


Observation:

Conclusion:

Extension activity:

1. Observations of the side of the test tube on pouring acid:

_________________________________________________________________________

2. Observations in lime water after passing the evolved gas:

(a) immediately after passing gas: __________________________________________

(b) after one minute: ______________________________________________________

_________________________________________________________________________

_________________________________________________________________________

NOTE: The above experiment can be repeated by taking 1-2 g of sodium hydrogen

carbonate in place of sodium carbonate.

Based on reaction between sulphuric acid and sodium hydrogen carbonate students may

be asked to design a soda acid fire extinguisher.

5. Acids react with carbonates to form ____________, ____________ and _____________


a. HCl + Na2CO3 Ý

b. HCl + KHCO3 Ý

c. HNO3 + NaHCO3 Ý

7. Explain with the help of chemical equation for the reaction occurring in fire

extinguisher.

WORKSHEET-6.1

107


ACTIVITY-7

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Neutralisation


Identify the products of a chemical reaction between an acid and a base.

Write the word equations for the observed chemical reaction

Write symbols and formulae for the reactants and products

Balance the chemical equation for the observed reaction.

Derive a general equation for neutralization reactions.

Understand and appreciate the function of an indicator to indicate completion of

a neutralization reaction.

+ -Acids release H into solution and bases release OH . If we were to mix an acid and base + -together, the H ion would combine with the OH ion to make the molecule H O, or plain 2

water:

+ -H (aq) + OH (aq) ÝH O2


This reaction called neutralization reaction of an acid with a base will always produce

water and a salt, as shown below:

HCl + NaOH ÝH O + NaCl2

HBr + KOH ÝH O + KBr2

To observe the reaction of acid with base using different strengths/concentrations of

base

Test tubes

Dilute NaOH solution

Dilute HCl solution

Phenophthalein solution

Part-I

1. Take about 2 mL of dilute NaOH solution in a test tube and add two drops of

phenophthalein solution.

2. Observe the colour of the solution.

3. Add dilute HCl solution to the above solution drop by drop until the pink colour of

reaction mixture is discharged.

4. Now add a few drops of NaOH to the above mixture.

5. Observe the change in colour of the reaction mixture.

6. Why do you think this has happened?

Acid Base Water Salt


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Aim:

Materials required:

Procedure:

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Part-II

The above activity may be performed in the form of a demonstration with the following

suggested variations. Students may be involved in the demonstration.

1. The teacher may also bring about the concept of concentration of an acid by carrying

out the activity in four test tubes marked A,B,C and D containing varying strengths/

concentrations of base ( NaOH).

2. The pH of all the four NaOH solutions should be found with the help of universal

indicator and recorded by the students. In the table provided.

3. The concentration of the acid used for neutralization is to be kept constant (HCl). The

pH of acid may be found and recorded.

4. The teacher may again reiterate the choice, use and need of indicator in this activity.

5. Let the students count the number of drops of acid required to change the colour of

the solution and neutralize the base.

Part-I

_________________________________________________________________________

_________________________________________________________________________

Part-II

A

B

C

D

Observations:

Test pH of the base Colour shown by Number of drops of acid

tube no. phenolphthalein required for complete

indicator neutralization

pH of acid=


Conclusion:

Suggestive remediation:

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

The above activity if performed with patience involving the students will prove

an excellent tool for removing misconceptions about strength and concentration

of an acid and base. The same activity may then be performed by choosing a

weak base sodium bicarbonate and strong acid HCl or a weak acid oxalic acid

and strong base NaOH.

Some students may find it difficult to write the chemical reaction involved and a

generalized chemical equation. Such students may be encouraged to memorise

the symbols and valencies from Table 3.6 on page 37 of Class IX, NCERT science

textbook and revise writing and balancing of chemical equations.

Some students may find it difficult to differentiate between the terms - a strong

acid/ base and a concentrated acid/ base. They may use the two terms inter

changeably, through this activity teacher may clarify this doubt.

Extra caution may be taken in explaining precautions to the students.

Attention of the students should be drawn towards how to add the acid slowly

with the help of a dropper without spilling any acid.

Development of observation skills in learners is an important expectation from

teaching/ learning of science. Special focus and attention may be given to this

aspect.

As this activity involves working with acid and base, the concentration of the

acids should not be more than 0.01M or even more dilute.

Approximately diluting 1mL of commercially available concentrated acid to 1L

aqueous solution. Note: For dilution, add acid to a large volume of water and not

the other way round

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Worksheet-7.1

Worksheet-7.2

0.4g of NaOH pellets may be dissolved in water to make a solution of 1L to get a

0.01M NaOH solution. Same NaOH solution may be diluted further in presence

of students to get solutions of varying concentrations.

Answer the following questions one by one as the chemical reaction demonstrated in

the class is taken forward:

Q1. Write the names of the reactants taking part in the chemical reaction during the

demonstration

Q2. List the observation (s) which justify that a chemical reaction has taken place.

Q3. Write a word equation and a balanced chemical equation for the complete chemical

reaction that has taken place.

Q4. Write a generalized equation for a neutralization reaction.

Q5. Which of the four test tubes contains higher concentration of the base?

Q6. Does pH of a solution change with dilution? .

Q Write balanced chemical equations for the following word equations:

a) Reaction of acid with metal

Calcium + Hydrochloric acid Ý Calcium chloride + Water

General equation:__________________________________________________________

Balanced equation:_________________________________________________________

b) Reaction of base with metal

Zinc + sodium hydroxide Ý sodium zincate + Water




c) Reaction of acid with metal carbonate

Calcium carbonate + Hydrochloric acid Ý Calcium chloride + carbon dioxide +Water



d) Reaction of acid with metal hydrogen carbonate

Sodium hydrogen carbonate + hydrochloric acid Ý sodium chloride + carbon dioxide +Water



e) Reaction of acid with metallic oxides

Magnesium oxide + Hydrochloric acid Ý magnesium chloride + Water



Students must be encouraged to recall and memorise the valency and symbol

table 3.6, given in class IX, NCERT science textbook on page 37 so that they may

be able to write the formulae of any given inorganic compound by just crisscross

of valencies and do not take to rote memorization of each formula.

Initially some students may find it difficult to generalize the reactions,

encourage them by writing more reactions of similar reactants on the board.

While carrying out the above worksheet, the teacher may also draw the attention

of the students towards categorizing the reactions into different types studied in

the previous unit of 'Chemical Equations and Reactions'.

An extension to the above worksheet may be designed by the teacher by asking

students to formulate their own reactions by taking reactants of their choice.

Another extension to the same may be done in the form of a game where

students of one team write reactants on the board and the members of the other

team suggest the products. All this will surely take the students away from rote

memorization of the reactions and will lead to appreciation of the chemical

reactions.

Suggestive Remediation

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Activity-8

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SALTS

Task:

The students will be able to:

Recall that an acid reacts with a base to produce salt and water.

Recognise the acid and base that would combine to give the given salt.

Correlate the acidic, basic or neutral nature of the salt to the strength of the acid

and base which may be used to obtain the salt

Appreciate that all salts are not neutral.

Conceptualise the formation and nature of a salt.

A salt is a compound formed by replacement of either all or a part of the ionisable hydrogen

atoms of an acid by some other cation

Acid + Base ÝSalt + Water

TYPES OF SALTS

1. Normal salts-.Salts formed by complete replacement of all the ionisable

hydrogen atoms of an acid by metallic or ammonium ions. For eg.NaCl, KNO , 3

Na CO , Na SO etc.2 3 2 4

2. Acid salts-Salts formed by partial replacement of ionisable hydrogen atoms of

an acid by metallic or ammonium ions. For eg. NaHCO , NaHSO , KH PO , 3 4 2 4

K HPO etc.2 4

3. Basic salts-Salt formed by partial replacement of hydroxyl groups of a base by

some other anion. For eg. Basic lead chloride Pb(OH)Cl , basic magnesium

bromide Mg(OH)Br etc.

Individual Worksheet


Procedure:

Assessment Parameters:

Q Complete the following table:

The students may be given the following worksheet of completing the table after the

teaching-learning of reaction between acid and base to form salt to strengthen the concept.

This worksheet may be used to introduce concept of 'salts' in the class.

Each of the following questions may be assessed giving equal weightage of 2 marks to each

salt. Marks may be converted to grades on a 10 point grade system.

Student Worksheet: Time: 30 minutes

Sodium chloride

Potassium nitrate

Zinc sulphate

Sodium acetate

Potassium carbonate

Copper chloride

Aluminium chloride

Sodium hydrogen carbonate

Ammonium chloride

Potassium sulphate

Salt Acid used Strong Base used Strong/ Predicted nature

/weak (S/W) weak (S/W) of the

salt- acidic,

basic or neutral

115


Suggestive Remediation

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Students must be encouraged to recall and memorise the valancy and symbol

table 3.6, given in class IX, NCERT science textbook on page 37 so that they may

be able to write the formulae of any given inorganic compound by just crisscross

of valencies and do not take to rote memorization of each formula.

Initially some students may find it difficult to identify the acid and base used to

make the salt, encourage them by telling them to write reactions of formation of

salts.

Students may be told that a salt of a-

strong acid + strong base = neutral

weak acid + strong base = basic

strong acid + weak base = acidic

weak acid + weak base = may be neutral, acidic or basic

While carrying out the above worksheet, the teacher may also draw the attention

of the students towards acid, base indicators.

The predictions made by the students may be checked with the help of litmus

paper or solution so as to strengthen their understanding.

An extension to the above worksheet may be designed by the teacher by asking

students to formulate their own salts by taking acids and bases of their choice.

A list of acids and bases with categories as strong and weak may be given to the

students a day in advance before administering this worksheet. A list is given

below to help.


Acids Strong/ weak

Bases Strong/ weak

2

Hydrochloric acid Strong

Sulphuric acid Strong

Nitric acid Strong

Phosphoric acid Weak

Acetic acid Weak

Oxalic acid Weak

Carbonic acid

Sodium hydroxide Strong

Potassium hydroxide Strong

Ammonium hydroxide Weak

Aluminium hydroxide Weak

Copper hydroxide Weak

Zinc hydroxide Weak

Another extension to the same may be done in the form of a game where

students of one team write name of a salt on the board and the members of the

other team write its formula and suggest the acid, base that may be used to form

that salt and predict the nature of the salt. All this will surely take the students

away from rote memorization of the concept.

117


ACTIVITY-9

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Some commonly used salts and their uses

COMMON SALT- NaCl- SODIUM CHLORIDE

1. Occurrence and extraction of common salt -The important sources of common

salt are-

Sea water- It is one of the main source of common salt. The sea water is allowed to

evaporate in shallow tanks under the influence of sun and wind. The salt

obtained contains impurities which are removed by suitable methods.

Rock salt- It is also found in the form of solid deposits in several parts of the

world. Due to presence of impurities it is often brown in colour and is called rock

salt. Rock salt is mined just like any other mineral.

Inland lakes- Large quantities of salts are obtained by the natural evaporation of

the water of inland lakes eg. Sambhar lake in Rajasthan(India) , Great salt lake

(USA) etc.

2. Uses-

It is an essential constituent of our diet.

It is used as a preservative for a number of food materials eg. In packed

meat and fish.

It is used for melting of ice on icy roads.

Mixed with ice it is used as freezing mixture eg. In making of icecreams.

It is an important starting material for the production of number of other

chemicals such as sodium, chlorine , hydrochloric acid , sodium hydroxide,

caustic soda(NaOH) , washing soda , baking soda etc.

CAUSTIC SODA-NaOH-SODIUM HYDROXIDE

1. Manufacture / Preparation- It is prepared by passing electricity through an

aqueous solution of sodium chloride (called brine) in a specially designed cell.

As a result of electrolysis chlorine gas is given off at anode and hydrogen gas at

the cathode. Sodium hydroxide solution is formed near cathode.This method is

called Chloro-alkali process because the products are chlorine and an alkali.


electricity

2NaCl(g) + 2H O(l) Ý2NaOH(aq) + Cl2(g) + H2(g)2

At anode :

- -2 Cl ÝCl + 2e2

At cathode :

+ -2 H + 2e ÝH2

3. Uses of Hydrogen-

In the manufacture of ammonia which is further used for the production of

various fertilizers.

In the hydrogenation of vegetable oils to form solid fats

In metallurgy to reduce heavy metal oxides to metals.

Liquid hydrogen is used as a rocket fuel.

Uses of Chlorine-

As a germicide and disinfectant for sterilization of water in the swimming

pools.

In the manufacture of bleaching powder, chloroform, hydrochloric acid,

etc.

In the manufacture of chlorofluorocarbon compounds used as refrigerants.

In the bleaching of wood pulp and cotton fabrics.

In the manufacture of PVC (poly vinyl chloride)

In the manufacture of pesticides.

4. Uses of Hydrochloric acid-

As a reagent in the laboratory.

In making aqua regia for dissolving gold and platinum.

For cleaning steel.

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In textile industry.

In the manufacture of medicines and cosmetics.

5. Uses of Caustic Soda-

In the manufacture of soaps and detergents.

For degreasing metals.

In the paper industry.

In making of artificial fibres like rayon etc.

In the manufacture of dyes.

In petroleum refining.

For mercerizing cotton, i.e. making cotton unshrinkable.

As a laboratory reagent.

BLEACHING POWDER-CaOCl -CALCIUM OXYCHLORIDE2

1. Manufacture / Preparation- It is prepared on industrial scale by passing

chlorine gas through dry slaked lime. The plant generally used for the

manufacture of bleaching powder is known as 'Hasenclever plant’

Ca(OH) + Cl Ý CaOCl + H O2 2 2 2

Slaked lime Chlorine Bleaching powder Water

2. Properties-

Bleaching powder is a yellowish white powder which gives strong smell of

chlorine.

It is soluble in water leaving behind a small residue of lime.

When bleaching powder is exposed to air, it reacts with atmospheric

carbon dioxide, giving off chlorine. To avoid decomposition it is packed in

air tight containers.

CaOCl + CO ÝCaCO + Cl↑2 2 3 2


2

2

2

2

2

When bleaching powder is treated with excess dilute acid, chlorine gas is

produced.

CaOCl + H SO → CaSO + H O + Cl↑2 2 4 4 2 2

Chlorine gas produced in this way is known as 'available chlorine'. It is this

available chlorine which is responsible for the bleaching action of the

bleaching powder.

3. Uses-

Bleaching powder is chiefly used for bleaching cotton and linen textiles,

wood and paper pulp.

It is strong disinfectant and is therefore, used for sterilization of water.

It is employed for making wool unshrinkable.

It is also used as an oxidizing agent in the manufacture of many chemicals.

BAKING SODA-NaHCO -SODIUM HYDROGENCARBONATE3

1. Manufacture / Preparation- Baking soda is obtained as primary product in

Solvay's process for the manufacture of sodium carbonate. In this process carbon

dioxide gas is bubbled through saturated ammonical brine solution which

results in the formation of baking soda.

NaCl + H O + NH + CO → NH Cl + NaHCO2 3 2 4 3

Ammonium Chloride Sodium bicarbonate

Sodium hydrogencarbonate is sparingly soluble in water whereas ammonium

chloride is highly soluble. Hence, sodium hydrogencarbonate separates out as

solid.

On small scale, it can be prepared in the laboratory by passing carbon dioxide gas

through aqueous sodium carbonate solution.

Na CO + H O + CO → NaHCO2 3 2 2 3

Sodium bicarbonate

121


2. Properties-

It is white crystalline solid.

It is sparingly soluble in water. The solution is alkaline in nature due to salt

hydrolysis.

NaHCO + H O → NaOH + H2CO3 2 3

Baking soda Sodium hydroxide Carbonic acid

(Strong base) (Weak acid)

Baking soda on heating decomposes to give carbon dioxide.

Heat

2NaHCO → Na CO + H O + CO↑3 2 3 2 2

It reacts with acids to liberate carbon dioxide gas with brisk effervescence.

2NaHCO + H2SO → Na SO + 2H O + 2CO↑3 4 2 4 2 2

3. Uses-

It is used as an ingredient in antacids. Being alkaline it neutralizes excess

acid in the stomach.

It is It is used as a component of baking powder (sodium

hydrogencarbonate + mild edible acid such as tartaric acid,citric acids

etc.)When mixed with water and heated, baking soda decomposes

producing carbon dioxide which causes bread or cake to swell and become

light. Tartaric acid present in baking powder neutralizes bitter taste of

sodium carbonate.

It is used in soda-acid fire extinguishers. Soda acid fire extinguishers

contain a solution of hydrogen carbonate and sulphuric acid. These two

chemicals are brought in contact by pressing a knob or by inverting the

extinguisher. Carbon dioxide is produced which forces a stream of

effervescing liquid on the fire. CO2 surrounds the combustible substance

and cuts off the supply of air. Thus the fire get extinguished.

2

2

2

2

2

2

2


WASHING SODA-Na CO .10H O-SODIUM CARBONATE DECAHYDRATE2 3 2

1. Manufacture / Preparation- Washing soda is prepared by Solvay's process. In this

process carbon dioxide gas is bubbled through saturated ammonical brine

solution which results in the formation of sodium hydrogencarbonate.

NaCl + H O + NH + CO → NH Cl + NaHCO 2 3 2 4 3

Ammonium Chloride Sodium bicarbonate

The sodium hydrogen carbonate is filtered off and then ignited to get sodium

carbonate.

Heat

2NaHCO → Na CO + H O + CO↑3 2 3 2 2

Anhydrous Sodium

Carbonate (soda ash)

The anhydrous sodium carbonate is dissolved in water and then subjected to

recrystallisation to obtain crystals of washing soda .

Na CO + 10H O → Na CO 10 H O 2 3 2 2 3 2

Washing soda (Hydrous salt)

2. Properties-

It is transparent crystalline solid.

It is readily soluble in water and its aqueous solution is alkaline in nature

due to hydrolysis.

Na CO + 2H O → 2NaOH + H2CO2 3 2 3

Sodium Carbonate Sodium hydroxide Carbonic acid

(Strong base) (Weak acid)

When kept open in the air, the crystals of washing soda lose nine molecules

of water of crystallization to form a monohydrate which is white powder.

Na CO 10 H O(s) → Na CO .H O(s) + 9H O(g)↑2 3 2 2 3 2 2

Transparent crystals White powder

The loss of water by a crystalline solid to the atmosphere on exposure to air

is called efflorescence.

2

2

2

123


2

2

2

2

2

2

2

2

On heating washing soda loses all the molecules of water of crystallization

and becomes anhydrous.

Heat

Na CO 10 H O(s) → Na CO (s) + 10H O(g)↑2 3 2 2 3 2

Washing soda Anhydrous Sodium

Carbonate (soda ash)

It reacts with acid to give out CO gas with brisk effervescence.2

Na2CO + H SO → Na SO + H O + CO↑3 2 4 2 4 2 2

Sodium sulphate

Washing soda reacts with soluble salts of calcium and magnesium present

in hard water to form insoluble salts of calcium and magnesium which can

be filtered off, Hence water becomes soft.

Na2CO3 + CaCl2 → CaCO3 + 2NaClCalcium chloride Calcium carbonate

Present in hard water Precipitate

3. Uses-

It is used in the laundry for cleaning clothes.

It is used in the manufacture of glass, borax, soap and caustic soda.

It is used in paper , paints and textile industries.

It is used for softening of hard water. It removes temporary as well as

permanent hardness.

It is used as an important laboratory reagent both in quantitative and

qualitative analysis.

NOTE-Water of crystallization is definite number of water molecules which are

present in loose chemical combination with one formula unit of the ionic solid in

crystalline form for eg. CuSO4.5H2O has 5 molecules of water of crystallization.


PLASTER OF PARIS-CaSO .1/2 H O-CALCIUM SULPHATE HEMIHYDRATE4 2

1. Manufacture / Preparation- It is prepared by heating gypsum to 393 K

393K

CaSO ..2 H O → CaSO .1/2 H O + 11/2 H O4 2 4 2 2

Gypsum Plaster of paris

The temperature should not be allowed to rise above 393K because above this

temperature, the whole water of crystallization is lost resuling into formation of

anhydrous calcium sulphate (dead burnt plaster).

Above 393K

CaSO ..2 H O → CaSO . + 2 H O4 2 4 2

Gypsum Dead burnt plaster

2. Properties-

It is a white powder.

When mixed with water and left for half an hour, it sets to hard mass . This

is due to rehydration of Plaster of paris to Gypsum

CaSO .1/2 H2O + 11/2 H O → CaSO .2 H O4 2 4 2

Plaster of paris Gypsum

3. Uses-

It is used for setting fractured bones in the right position and in making

casts in dentistry.

In making toys, casts for statues, decorative materials, jewellery and

cosmetics.

In making the surface smooth, e.g. that of walls, ceiling etc, before paint.

In making chalks for writing on the black board.

In laboratory, for making the apparatus air tight by sealing the gaps at the

stopper etc.

In making fire proof materials

2

2

2

2

2

2

2

2

125


PREPARATION OF ZINC SULPHATE

PREPARATION OF Copper sulphate

Zinc sulphate can be made by reacting dilute sulphuric acid with zinc granules.

Zn(s) + H SO (aq) → ZnSO (aq) + H (g)2 4 4 2

Zinc Sulphuric Acid Zinc sulphate Hydrogen

The steps involved are:

a) Add excess zinc granules to the acid in a beaker, when zinc starts to dissolve and

hydrogen bubbles off. Wait till effervescence is over which indicates that all the

acid is used up.

b) Remove excess zinc by filtration.

c) Transfer the clear aqueous solution of zinc sulphate in an china dish. Heat the

solution to evaporate some water. Allow to cool, when colorless crystals of zinc

sulphate begin to appear.

This method Is good for preparation of salts of Al, Fe, Mg. However, Cu, Ag, Au do not

react at all. On the other hand, Na, K react very violently with acids.

In order to make salts of Cu, start with an insoluble base like CuO and react with acid.

(a) Dissolving zinc in dilute sulphuric acid(b) Filtration of zinc sulphate solution(c) Evaporation of the zinc sulphate solution

Zinc sulphatesolution

Zinc

Dilutesulphuricacid

(a) (b) (c)

CuO (s) + H SO (aq) CuoSO + H O (I)2 4 4 2 (aq)

Copper oxide Sulphuric acid Copper sulphate Water


Steps followed are:

a) Take CuO in a beaker and add dil. Sulphuric acid. Warm the mixture when the

metal oxide dissolves and the solution turns blue.Add more CuO till no more

dissolves.

b) Remove excess solid by filtration

c) Transfer the blue solution of copper sulphate in an china dish. Heat the solution

to evaporate some water. Allow to cool, when blue crystals of copper sulphate

begin to appear

Na is too reactive for a reaction with acid . Instead we can use NaOH to make sodium salts.

Sodium sulphate can be prepared by treating sodium hydroxide solution with dilute

sulphuric acid.

As both the reactants and products are aqueous, we have to make sure that all the reactants

are used up. This can be done as follows

(i) Take dilute sulphuric acid in a burette.

(ii) Take 20 ml of sodium hydroxide solution in a conical flask.

(iii) Add a drop of phenolphthalein to the sodium hydroxide solution to turn the

solution deep pink in color.

(iv) Keep the conical flask beneath the nozzle of the burette, and open its tap to let the

acid come down drop by drop into the conical flask.Keep stirring the conical

flask.

(v) At a point of addition of the acid, the pink color in the conical flask suddenly

turns colorless. This shows that all the alkali has been used up. Close the tap.

(vi) Transfer the solution into an evaporating dish and carefully evaporate to

dryness.

(vii) Colorless crystals of sodium sulphate appear.

PREPARATION OF SALTS OF Na

127

H SO (aq)2 3

Sulphuricacid

+ Na SO (aq)2 4

Sodiumsulphate

2H O(I)2

Water+2NaOHl(aq)

Sodiumhydroxide


PREPARATION OF INSOLUBLE SALTS

Salts that are soluble have been prepared by evaporation. Not all salts are soluble.

All sodium, potassium and ammonium salts

All nitrates

Most Chlorides silver and lead chloride

Some sulphates Barium, calcium and lead sulphate

Sodium, potassium, ammonium Carbonates All carbonates

Insoluble salts are prepared by precipitation

Calcium Carbonate

(i) Take calcium chloride in a beaker and dissolve it in water.

(ii) In another beaker dissolve sodium carbonate in water.

(iii) Add the sodium carbonate solution into calcium chloride solution and stir well.

Reaction occurs and a white precipitate is formed.

Soluble Salts Insoluble salts

CaCl (aq)2

Calciumchloride

Na CO (aq)2 3

Sodiumcarbonate

+ 2NaCl(aq)Sodiumchloride

CaCO (s)3

Calciumcarbonate

+


(iv) The white precipitate formed is of calcium carbonate. Filter the precipitate and

dry it. The white powder when dried on the filter paper is calcium carbonate salt

Mixing solutions of Barium chloride and sodium sulphate gives barium sulphate.

BaCl (aq) + Na SO (aq) → BaSO (s) + 2 NaCl(aq)2 2 4 4

Steps used are:

a) Make a solution of BaSO as well as a solution of Na SO .4 2 4

b) Mix the two solutions by slowly transferring one into the other and with

constant stirring. A white precipitate of barium sulphate will form at once.

c) Filter the precipitate and dry in oven.

1. A white substance having a strong smell of chlorine is used to clean water storage

tanks. Identify the substance. Give its chemical name and write the chemical equation

for its preparation.

2. When the concentrated aqueous solution of substance X is electrolysed, then NaOH,

Cl and H are produced. Name the substance X. What is the name of this process.2 2

3. Write the Chemical formula of washing soda. What happens when the crystals of

washing soda are left exposed to air?

4. What colour change would you observe on adding red litmus solution to an aqueous

solution of washing soda?

5. Write an equation to show the reaction between Plaster of Paris and water.

6. What will happen if a solution of sodium hydrogen carbonate is heated?

7. A compound X is obtained by heating compound Y at 373 K. When compound X is

mixed with water, crystals of Y are produced. Identify compound X and Y and give

two uses of X.

Barium Sulphate

Work Sheet-9.1

129


8. A blue salt becomes white on heating. With the help of a reaction explain the change in

colour.

9. A blue salt becomes white on heating. With the help of a reaction explain the change in

colour.

10. What happens when electric current is passed through brine.

11. A compound of sodium forms a white powder. It is a constituent of baking powder

and is used in some antacid preparations. When heated, X gives out a gas and steam.

The gas forms a white precipate with lime water. Write the chemical formula and

name of X and the chemical equation for its decomposition on heating.

12. What is bleaching powder? How is it prepared? Write chemical equation involved in

the preparation of bleaching powder. Write two uses of bleaching powder.

13. Name four salts you could make by precipitation

14. Name four salts you could make by evaporation

15. Name the acid and metal used to make:

a) Potassium chloride

b) Magnesium nitrate

16. Give the possible starting compounds to make the following salts

a) Lead chloride

b) Calcium sulphate

c) Magnesium carbonate

d) Lead carbonate

The process of identifying unknown cations or anions in a solution is called Anion and

Cation analysis

ACTIVITY 10

Qualitative Analysis of Anions and cations


Test for ANIONS

CARBONATE

Only the alkali metal and ammonium carbonates are water soluble.

Dilute hydrochloric acid gives vigorous effervescence with carbonates, evolving carbon

dioxide that turns lime water milky:

2- +CO (aq or s) + 2H (aq) → H O(l) + CO (g)3 2 2

CO (g) + Ca(OH) → CaCO (aq) +H O(l)2 2 3 2

CHLORIDE:

AgCl, PbCl , Hg Cl and CuCl are insoluble in water.2 2 2

Silver nitrate solution added to a solution of a chloride that has been acidified (test with

blue litmus paper) with dilute nitric acid gives a white precipitate of silver chloride. The

precipitate is readily soluble in dilute ammonia .

Ag+(aq) + Cl-(aq) → AgCl(s)

+ -AgCl(s) + NH (aq) → [Ag(NH3) ] (aq) + Cl (aq)2 3 2

IODIDE:

Silver nitrate solution added to a solution of an iodide that has been acidified (test with blue

litmus paper) with dilute nitric acid gives a yellow precipitate of silver iodide. The

precipitate is insoluble even in concentrated ammonia:

+ -Ag (aq) + I (aq) → AgI(s)

SULPHATE

BaSO , SrSO and PbSO are insoluble; Ca SO is sparingly soluble.4 4 4 4

Barium nitrate solution added to the test solution acidified with dilute hydrochloric acid

gives a white precipitate of barium sulphate:

Ba +(aq) + SO4 -(aq) → BaSO (s)2 2 4

131


NITRATE

Nitrate ions are reduced to ammonia by boiling with aluminium in sodium hydroxide

solution. Warm the test solution with NaOH and test the vapour for ammonia- the gas that

turns moist red litmus paper blue indicating nitrate in the original solution:

- - -3NO (aq) + 8Al(s) + 18H O(l) + 21 OH (aq) → 8[Al(OH) ] (aq) + 3NH (g)3 2 6 3 3

CATIONS

3+Aluminium, Al

Sodium hydroxide solution precipitates white gelatinous aluminium hydroxide. This

reacts with excess NaOH to give a colourless solution of sodium aluminate:

3+ -Al (aq) + 3OH (aq) → Al(OH) (s) 3

- 3-Al(OH) (s) + 3OH (aq) → [Al(OH) ] (aq)3 6

Ammonia solution precipitates white aluminium hydroxide, as with NaOH; however it

does not react further with excess ammonia.

+NH4

Alkalis (sodium hydroxide, calcium hydroxide) liberate ammonia from ammonium salts

on warming with the solution, or even from a mixture of the solids.

+ -NH (aq) + OH (aq) → NH (g) + H O(l)4 3 2

The test solution is warmed with sodium hydroxide solution and the vapours tested with

moist red litmus paper. It is important to test the vapours immediately heating begins,

since the ammonia is lost very quickly and by the time the solution boils it may well have all

gone.

Calcium,Ca2+

Sodium hydroxide solution gives white ppt that remains insoluble.

-Ca +(aq) + OH (aq) → Ca(OH) (s) 2 2

With ammonia , little or no reaction occurs.


Copper(II)

Sodium hydroxide solution gives a pale blue precipitate usually described as copper(II)

hydroxide:

2+ -Cu (aq) + 2OH (aq) → Cu(OH) (s)2

Ammonia solution initially gives a blue precipitate as for sodium hydroxide. Further

addition of ammonia gives deep blue solution.

Fe(II)

Sodium hydroxide solution precipitates dirty green iron(II) hydroxide.; on standing the

surface of the precipitate turns foxy-red owing to air oxidation to iron(III) hydroxide:

2+ -Fe (aq) + 2OH (aq) → Fe(OH) (s) 2

Ammonia solution behaves similar to sodium hydroxide.

Zinc(II)

Sodium hydroxide solution precipitates white zinc(II) hydroxide, easily soluble in excess

sodium hydroxide to give sodium zincate(II), because the hydroxide is amphoteric:

-Zn (aq) + 2OH (aq) " Zn(OH) (s) 2+ 2

- 2-Zn(OH) (s) + 2OH (aq) " Zn(OH) (aq)2 4

Ammonia solution initially precipitates zinc(II) hydroxide, as with sodium hydroxide.

Excess ammonia causes the precipitate to disappear.

133

Test for anions

anion test test result2-carbonate (CO )3 add dilute acid effervescene, carbon dioxide

produced-chloride (Cl )

(in solution)acidify with dilute nitric acid, thenadd aqueous silver nitrate

white ppt.

-iodide (1 )(in solution)

-nitrate (NO )3

(in solution)2-sulfate (SO )4

(in solution)

acidify with dilute nitric acid, thenadd aqueous silver nitrate

add aqueous sodium hydroxidethen aluminium foil, warm carefully

acidify with dilute nitric acid, thenaqueous barium nitrate

yellow ppt.

ammonia produced

white ppt.


Gas Test and test results

Activity

Ammonia(NH ) Turns damp red litmus paper blue3

Carbon dioxide (CO ) Turns limewater milky2

Chlorine(Cl ) Bleaches damp litmus paper2

Hydrogen (H ) 'Pops' with a lighted splint2

Oxygen(O ) Relights glowing splint2

You are provided with solid E.

Carry out the following tests on E, recording all of your observations in the table.

Conclusions must not be written in the table

Test for aqueous cations

cation

3+aluminium (Al )

+ammonium (NH )4

2+calcium (Ca )2+copper (Cu )

2+iron (II) (Fe )3+iron (III) (Fe )

2+zinc (Zn )

effect of aqueous sodium hydfroxide

white ppt., soluble in excess giving a colourless solution

ammonia produced on warming

white ppt., insoluble in excess

light blue ppt., insoluble in excess

green ppt., insoluble in excess

red-brown ppt., insoluble in excess

white ppt., insoluble in excessgiving a colourless solution

effect of aqueous ammonia

white ppt., insoluble in excess

-

no ppt., or very slight white ppt.

light blue ppt., soluble in excessgiving a dark blue solution

green ppt., insoluble in excess

red-brown ppt., insoluble in excess

white ppt., soluble in excessgiving a colourless solution


tests

(a) Describe the appearance of solid E.

(b) Place half of solid E in a test-tube.

Heat the test tube gently.

Test any gas given off with damp pHindicator paper.

(c) Add the rest of solid E to about 8 cm³ of distilled water in a test-tube.

Cork the test-tube and shake the contents until dissolved.

Divide the solution into 4 equal portions in test-tubes and carry out the following.

(i) Add several drops of aqueous sodium hydroxide to the first portion of the solution and shake the test-tube.

N o w a d d e x c e s s s o d i u m hydroxide to the test-tube.

(ii) Repeat test (i) using aqueous ammonia solution instead of aqueous sodium hydroxide.

(iii) Test the pH of the third portion of the solution with indicator paper. Now add to the solution a b o u t 1 c m ³ o f d i l u t e hydrochloric acid followed by about 1 cm³ of barium chloride solution.

(iv) To the fourth portion of the solution add an equal volume of aqueous sodium hydroxide. Now add a small spatula measure of aluminium powder and warm the mixture carefully. Test any gases given off.

................................................................. (1)

..........................................................................

.................................................................... (2)

..........................................................................

..........................................................................

.................................................................... (3)

..........................................................................

.................................................................... (2)

pH.............................................................. (1)

.................................................................... (1)

..........................................................................

.................................................................... (2)

observations


Table of Qualitative solubility (Solubility rules)

To use table

Combine Negative ion in column A with positive ion in column B, read across table to

determine solubility.

Example: ZnSO 4

2-Find SO : read across, 4

2+Zn is not part of first group,

therefore part of All other positive ions

therefore soluble

All negative ions are_____with Alkali ions ( Li, Na, K etc) Soluble

+All negative ions are ____ with Hydrogen ( H ) Soluble

+All negative ions are ____ with Ammonium ion (NH ) Soluble4

-Nitrate NO ions are ____ with All positive ions are Soluble3

- + 2+ +Chloride, Cl Ag , Pb , Cu ----> Insoluble

(have low solubility)

-Iodide I All Other positive ions----> Soluble

2- 2+ 2+ 2+Sulfate SO Ba , Sr , Pb -------> Insoluble 4

All Other positive ions -----> Soluble

2- + +Carbonate CO Alkali Ions, H , NH Soluble 3 4

All Other positive ions Insoluble

2

2

2

2


Activity

Using solubility rules

Write out the formula for each of the following ionic compounds ant then using the table of

relative solubility given above, predict the solubility of the following ionic compounds.

a) Zinc chloride

b) Ammonium carbonate

c) Zinc(II) sulfate

d) Copper (I) Iodide

e) Sodium iodide

f) Calcium sulfate

g) Magnesium nitrate

h) Potassium sulfate

i) Barium chloride

j) Iron (II) carbonate

136


Revision worksheet-1

Complete the following cross word puzzle by taking the clues given-

1

2

3

9

6 7

5

4

8

10

11

13

14

15

12


Down

1. name of process of electrolysis of aqueous sodium chloride (2 words)

2. Change in colour of litmus in basic medium (3 words)

4. chemical name of washing powder (2 words)

5. medicine for acidity and indigestion.

6. common name of sodium hydrogen carbonate (2 words)

7. Change in colour of litmus in acidic medium (3 words)

8. Gas released when an active metal reacts with an acid.

9. common name of calcium sulphate hemihydrate (3 words)

12. Acids and bases react to produce water and --

Across

1. Gas released when a metal carbonate reacts with an acid (2words)

3. This indicator gives reddish pink colour in acidic solution (2 words)

10. mixture of sodium hydrogen carbonate and tartaric acid to make cakes (2 words)

11. Common name of dilute solution of acetic acid

13. This indicator gives magenta pink colour in alkaline solution

14. Acids and bases react to give --------------- reaction

15. Plaster of Paris is obtained by heating


Revision Worksheet 2

Cross-Word Puzzle-2

Complete the following crossword puzzle by taking the clues given below-

Across:

2 Acids on your skin! (8)

5 The pH measure? (5)

7 Plants can't grow if it is too acidic. (4)

8 If the pH is over 7. (8)

10 Colour of litmus in acid. (3)

12 You can extract these coloured

materials from plants. (7,4)

Down:

1 1st name of a well known strong acid,

(9)

2 To test for how acidic or alkaline a

solution is. (9)

3 Latin for water (3)

4 The pH number of a strong acid. (3)

5 This kind of acid dissociates

completely in water. (6)

1 2 3 4 5 6

7 8 9

10

11

12 13 14 15 16

16

1918

20 21

22

23

2624 25

27

28 29 30 31

32

33

4

36

35


14 Some treated with weak acid, some

with weak alkali, depends on the

insect! (5)

17 In the list, only just acid. (4)

18 The pH of strong acids. (3)

21 This fruit has acidic juice, good to

make a cool drink. (5)

22 Spilt concentrated acid is one! (6)

23 We can get natural acid from some. (5)

24 Used to neutralise stomach acid! (7)

26 The pH of a strong alkali. (4)

31 Common name for a well known

weak acid used in food preparation.

(7)

32 1st name of a well known acid (12)

33 This type of acid won't cause harm if it

spills on you! (4)

34 "My dear Watson, this

perfectly describes the

effect of 'prussic acid' on

the victim"! (5)

35 It turns litmus blue. (6)

36 a well known strong alkali (6,9)

6 Put on soil that is too acid for healthy

plant growth. (4)

8 If the universal indicator turns red it

means? (6)

9 If the universal indicator turns green it

means? (7)

11 A well known indicator. (9)

13 This doesn't like too much acid, but

just enough for digestion! (7)

15 The colour of universal indicator in a

very strong alkali. (6)

16 The pH of a neutral solution. (5)

19 is its symbol. (9)

20 The hazard warning sign for this is a

cross. (7)

25 It neutralises an alkali. (4)

27 It means very corrosive and 'soda' is

an example! (7)

28 The name of the acidity and alkalinity

scale. (2)

29 This chloride is 'common salt'. (6)

30 The pH of a very weakly acid solution.

(3)

141

Resource: http://www.docbrown.info/ks3chemistry/ks3chemistry.htm


Revision worksheet-3

Some incomplete word equations are given to you. Complete these by filling in the

blanks-

1. zinc + hydrochloric acid ===> __________________________ + hydrogen

2. _______________________ + sulphuric acid ===> copper(II) sulphate + water +

carbon dioxide

3. magnesium oxide + ___________________________ ===> magnesium nitrate + water

4. zinc + sulphuric acid ===> zinc sulphate +

5. magnesium hydroxide + hydrochloric acid ===> __________________________ +

water

6. ________+ nitric acid ===> copper(II) nitrate + water + _________________

7. zinc carbonate + sulphuric acid ===> ________ + _____ + carbon dioxide

8. iron +______________ ===> iron(II) chloride + hydrogen

9. magnesium oxide + hydrochloric acid ===> __________________ +

_______________

10. _____________ + hydrochloric acid ===> calcium chloride + water +

________________

11. _________________________ + sulphuric acid ===> magnesium sulphate +

hydrogen

12. magnesium + nitric acid ===> ________________________ + hydrogen

13. zinc hydroxide + ________________________ ===> zinc chloride + water

14. _______________ + hydrochloric acid ===> magnesium chloride + water + carbon

dioxide

15. aluminium + hydrochloric acid ===> ________________________ + hydrogen

16. sodium hydroxide + hydrochloric acid ===> ___________ + ____________


17. sodium carbonate + ___________ ===> sodium sulphate + water + ______________

18. ____________ + nitric acid ===> calcium nitrate + water + carbon dioxide

19. _________________ + sulphuric acid ===> iron(II) sulphate + hydrogen

20. zinc oxide + __________________ ===> zinc chloride + water

21. copper(II) carbonate + sulphuric acid ===> _________ + water + carbon dioxide

22. aluminium + ___________________ ===> aluminium sulphate + hydrogen

23. calcium oxide + hydrochloric acid ===> _____________ +_______________

24. magnesium hydroxide + ___________ ===> magnesium sulphate + __________

25. ammonia + sulphuric acid ===> ____________________

26. ammonia + ________________ ===> ammonium chloride

27. zinc hydroxide + sulphuric acid ===> _____________ + ____________

28. copper(II) oxide + hydrochloric acid ===> __________________ + water

29. sodium hydroxide + sulphuric acid ===> ____________________ + water

30. sodium hydrogencarbonate + hydrochloric acid ===> _______ + _________ +

__________

31. ammonia + _________________ ===> ammonium nitrate

32. calcium oxide + ______________ ===> calcium chloride + _____________

33. aluminium hydroxide + nitric acid ===> ___________________ + water

34. calcium carbonate + _________ ===>calcium ethanoate + _______ + _________

35. ethanoic acid + magnesium ===> ______________ + hydrogen

36. _________________ + magnesium oxide ===> magnesium ethanoate + _________

37. sodium hydroxide + _________ ===> ___ ethanoate + _________

http://www.docbrown.info/page04/Y11revQs/acidreactionequationsFH.htm

Resource:


Revision Work Sheet- 4

Choose the correct option for the following questions from the four choices given. Each

question has only one correct answer.

Q1. An element common to all acids is

a) Chlorine

b) Nitrogen

c) Oxygen

d) Hydrogen

Q2. Bases on ionization release

a) hydrogen ions

b) sodium ions

c) chloride ions

d) hydroxide ions

Q3. In general, salts

a) are ionic compounds

b) contain hydrogen ions

c) contain hydroxide ions

d) turn litmus red

Q4. When water solutions of an acid and base are mixed

a) no reaction occurs

b) a new acid and a new base are formed

c) a salt and water are formed

d) an acid and a salt are formed

Q5. When magnesium and hydrochloric acid react, they produce

a) Oxygen and magnesium chloride


b) Chlorine and magnesium oxide

c) Hydrogen and magnesium chloride

d) Hydrogen and magnesium oxide

Q6. When HCl(aq) is exactly neutralized by NaOH(aq), the hydrogen ion concentration

in the resulting mixture is

a) always less than the concentration of the hydroxide ions

b) always greater than the concentration of the hydroxide ions

c) always equal than the concentration of the hydroxide ions

d) sometimes greater and sometimes less than the concentration of the hydroxide

ions

Q7. A common substance that contains acetic acid is

a) Vinegar

b) Ammonia water

c) Salad oil

d) Soap

Q8. A base used in the manufacture of soap is

a) Calcium hydroxide

b) Sodium hydroxide

c) Ammonium hydroxide

d) Zinc hydroxide

Q9. Which of the following solution will turn phenolphthalein pink?

a) HCl(aq)

b) CO (aq) 2

c) KOH(aq)

d) CH OH(aq) 3


Q10. Fruit juices, such as orange juice, contain:

a) Boric Acid

b) Citric Acid

c) Sulphuric Acid

d) Nitric Acid

Q11. When dissolved in water, salts

a) Are non-electrolytes

b) Have a bitter taste

c) Are electrolytes

d) Release hydrogen ions

Q12. A base can be prepared by the reaction between

a) An active non-metal and water

b) A gas and water

c) A sulphide and water

d) An active metal and water

Q13. Of the following, the property that most closely relates to acids is

a) A bitter taste

b) Contains the hydroxide ion

c) Sour taste

d) Salty taste

Q14 A solution turns red litmus to blue. It's pH is likely to be:

a) 2

b) 5

c) 7

d) 10


Q15. Which formula represents a base?

a) KOH

b) KCl

c) CH OH 3

d) CH COOH 3

"Which is the most effective antacid?"

Scientific progress is made by asking meaningful questions and conducting careful

investigations. As a basis for understanding a concept students should develop their own

questions and perform investigations. As inquiry based approach is not dealt with the

grade so far, the inquiry question will be provided to the learners.

The learner will be able to

Conceptual understanding:

[The conceptual understanding targeted is limited and extension may vary from section to

section as per the need of the class.]

The targeted conceptual understanding:

1. Understanding of the terms acid, base, salt and neutralization

2. Familiarity with various examples associated with the above four terms

3. Correlation of the above four terms in daily life context

Experimentation and investigation (EI):

1. support hypothesis logically

2. design an experiment in logical sequence to test the hypothesis

Extension Activity

Chemistry Investigation (Content: Acids and bases)

Objective:

Learning outcome:


3. identify resources required for the experiment and use the same appropriately and

judiciously

4. conduct multiple trials to test a prediction and draw conclusions about the

relationships between predictions and results.

5. record data by using appropriate graphic representations (including charts, graphs,

and labelled diagrams) and make inferences based on those data.

6. write instructions others can follow to carry out the procedure

7. validate the result and conclusion using existing literature

8. write a report of the investigation that includes conducting tests, collecting data,

comparing with existing literatures and drawing conclusions.

9. include feedback to modify the investigation.

Inquiry question: Which antacid can neutralize the stomach acid satisfactorily?

Plan 1: Brainstorming session

EQ: Why do people say that they are suffering from acidity? What does that mean? What

do they do to avoid acidity?

Proceedings: (S) need to put their understanding (can be in the form of web) in the

notebook individually and then (T) needs to ask (S) to share. The same will be put down on

the blackboard. (T) will not share her understanding with the class.

Plan 2: Investigation

Proceedings: Various reading materials will be provided to (S) for them to have discussion

in groups on the previous class questions. [Reading material: books n few authentic

readings from net]

Plan 3: Presentation

Proceedings: Each group to present what they have understood from the previous

readings and discussions. Once a group finishes they are required to present their

understanding, the other groups can ask questions or add input to enrich the

understanding for the class as a whole.

Plan 4: Brainstorming session

Transaction:


EQ: Which antacid can neutralize the stomach acid satisfactorily?

Proceedings: (S) will discuss what an antacid is and what is the meaning of neutralization?

(S) will brainstorm on how to proceed to find the method to reach to the answer. (S) need to

bring antacids from the market (one tablet each) and would proceed in the next class to

practically find the answer of the EQ.

Plan 5 + 6: Writing steps

Proceedings: (S) will write their plan in steps for the experiment in the respective groups.

(T) will observe each group and depending upon the status will support.

Guidelines for (T) during guidance:

1. check weather the groups have written EI 1-3.

2. brainstorm in groups regarding the resources; (cost factor, easy accessibility, proper

storage after and during use, safe ways of discarding)

3. check EI 5. Discuss various ways of doing the same.

4. Discuss EI 4. (What should be done to make our results accurate and authentic?

(T) will encourage (S) to keep more than good no. of experimental set ups.)

Plan 7 + 8: Performing the experiment (no. of periods will depend upon the design by each

group)

Proceedings: (T) will inform the expectation to all groups before they start with the

experiment. (give photocopies)

Expectation: All (S) need to submit a report of their investigation that must include

a. hypothesis with reason

b. resources used

c. procedure (must also includes multiple trials also)

d. regular observation (table, diagram etc. ) + representation of observation (any

graphic organizer/graph)

e. result

f. research of existing literature (details need to be shared later)


g. comparison of result and literature to write conclusion.

h. moments of joy and sorrow during the investigation

(S) will perform the designed experiment.

Plan 9 + 10 : Compilation of the experiment

Proceedings: (S) will compile all work as mentioned above (a-e). (T) will assist by

reminding (S) about the pointers.

Plan 11+ 12: Reading literature

Proceedings: (S) will be provided with various reading materials in the class. Each group

will be provided with same set. (S) need to read, identify the earlier findings and compare it

with their results. (S) need to identify if there is any mismatch of literature with their results

and brainstorm the reasons for so. (S) will work on point (g).

Assignment: h. Write moments of joy and sorrow during the investigation.

Extension: If possible (S) can be allowed to find out more on given sites in their computer

period. (optional)

Plan 13+ 14 + 15: Feedback to other groups

Proceedings: (S) will be asked to share previous day's assignment with the class. Work of

(S) need to be displayed group-wise. Each group will move to the other group's work and

will look at the same and will complete the feedback form for that group. 15 mins will be

given to go through per group's work.

Plan 16 + 17: Working on Feedback

Proceedings: Each group will read their group's feedback form and will try to incorporate

the required changes in their work.

SCIENCE UNIT-1chemistry

Rubrics of Assessment for Learning

Beginning

(1)

Parameter

Learner is able to

•

•

•

•

•

Define acids and

bases in terms of H+

and OH-

List and explain

characteristic

properties of acids

and bases.

Define acidity and

alkalinity in terms of

pH

Identify and describe

strong and weak

acids and bases.

Understand the

concept of acids and

bases in our daily

routine

151

Approaching

(2)

Meeting

(3)

Exceeding

(4)


Beginning

(1)

Parameter

Learner is able to

•

•

•

•

Describe the role of

antacids and

understand

neutralization using

real life problems.

Identify acidic, basic

and neutral oxides.

Explain the

preparation of salts

and their nature.

Identify carbon

dioxide, hydrogen

gases.

Approaching

(2)

Meeting

(3)

Exceeding

(4)

2 CHEMISTRY SCIENCE UNIT-1 - NIMS · PDF fileWorksheet-3.1 Content 3 pH of acids, bases and...

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