Amarchand Singhvi International School

Subject : Science

Class : VII

Chapter : Acids, Bases and Salts

Topic : Acids, Bases, Indicators and

Neutralization.

Teacher : Ms. Heemani Joshi

E-Learning Programme

1. Acids

(i) Organic Acids

• The acids which are found in plants andanimals are called as organic acids.

• Tartaric acid is mixed with baking sodaand is used in making cakes andbiscuits.

• Acetic acid is used in pickles andtomato ketchup.

Amarchand Singhvi International School

• The substances which are sour in taste are called as ACIDS.• The word acid comes from the Latin word ‘acidus’ which means

sour in taste.• Acids are of two types • (i) Organic Acids and • (ii) Mineral Acids.

(ii) Mineral Acids.

• The acids prepared from theminerals of the earth are calledas mineral acids.

• They are human made acidsand are also known asLaboratory made acids.

• Most commonly used acids are:

Amarchand Singhvi International School

❑ Dilute and Concentrated Acids:-

Amarchand Singhvi International School

• An Acid can be diluted orconcentrated dependingupon the amount of waterpresent in it.

(a) Dilute Acids:-• The acidic solution which

has large quantity of waterand small quantity of acidis called Dilute Acid.

(b) Concentrated Acids:-• The acidic solution which

has a small quantity ofwater and large quantityof acid is calledConcentrated Acid.

2. Bases

Amarchand Singhvi International School

• The substances which are bitter in taste and have soapy touch are called as bases.

• The nature of such substances is said to be basic.• E.g.:- Baking Soda , Sodium Hydroxide, calcium

Hydroxide and Magnesium Hydroxide.

Bases used in LaboratoryBases are also referred to as “ALKALI”

3. Neutral Substances

Amarchand Singhvi International School

• Those substances which are neither acidic nor basic in nature.

• Properties of neutral substances are as follows:• Neutral substance don’t show any effect on litmus paper• Neutral substance neutralize acid and base reactions.• E.g.:- Pure Water(Distilled water), Glucose, Sugar and Salt.

4. Indicators.

Amarchand Singhvi International School

• Indicators are used to test whether the substance is acidic or basic in nature.

• They are special substances which have different colors in acidic and in basic mediums.

▪ How do they work?

• The indicators change their color when added to a solution containing acidic or basic substance.

• Indicators are of following types:

• (i) Natural Indicator - Turmeric,

Litmus, China Rose, Red cabbage

juice.

• (ii) Human Made Indicators –

Phenolphthalein, Methyl orange.

❑Properties of Acids:

Amarchand Singhvi International School

• Acids are sour in taste.• Acids are soluble in water.• All Acidic solutions conduct electricity.• Acids turns blue litmus red.• Acids are corrosive in nature. They can destroy paper, cloth,

metal etc. Thus, acids are stored in glass containers instead of metal containers.

• Most of the acids react with metals to form hydrogen gas and their respective salts.

• Most of the acids react with metal carbonates to form their respective salts , water and carbon di oxide.

Mg + 2HCl MgCl2 + H2

Na2Co3 + H2 So4 Na2So4+ Co2+ H2O

❑ Properties of bases

Amarchand Singhvi International School

• Bases generally have bitter taste.• They are soapy or slippery to touch.• They turn red litmus to blue.• They are corrosive in nature as they corrode wood, paper, skin etc.• Basic solutions conduct electricity.

5. Neutralization.

Amarchand Singhvi International School

• The reaction in which an acid reacts with a base to form salt and water is called Neutralization.

• Some heat is always evolved in neutralization reaction, due to which reaction temperature rises.

• A neutralization reaction can be represented as follows:-

• Salt does not mean common salt. It is general term used for compound formed by neutralization of acid and base.

Acid + Base Salt + Water+ Heat

❑ Properties of Salt:-

Amarchand Singhvi International School

• Salts exist in solid state.• They have high melting and boiling points.• Most of the salts are soluble in water.• Salt solutions are good conductors of electricity.

• 6. Neutralization in everyday life

• (i) Indigestion

Amarchand Singhvi International School

• On consumption of spicy food, thestomach produces a large amountof hydrochloric acid which leads tothe acidity in stomach.

• This condition is called asIndigestion.

• In order to cure indigestion, wetake weak bases called “antacids”such as milk ofmagnesia(MagnesiumHydroxide).

• It neutralize the effect of excessiveacid.

• (ii) Soil Treatment

Amarchand Singhvi International School

• Plants grow well in neutralsoil. Neutralization reactioncan help to neutralize acidicand basic soil in followingways:-

a. Acidic Soil• Excessive use of chemical fertilizer makes the soil acidic.• Acidic soil can be treated with bases such as Quicklime (Calcium Oxide) or

Slaked Lime( Calcium Hydroxide).• These bases neutralize the excess acids present in soil and hence soil

becomes neutral.b. Basic Soil• When the soil is too basic.• Decaying organic matter or compost is added to the soil.• Manure releases acids which neutralize the basic nature of soil.

Amarchand Singhvi International School

• The sting of ant or bee inject a formic acid into the skin of person.• The injection of formic acid causes painful burning and swelling

reaction into the skin of person.• The effect of sting can be neutralized by rubbing a mild base like

baking soda (sodium hydrogen carbonate) or calamine solution• ( Zinc Carbonate) .

(iv) Factory Wastes.

Amarchand Singhvi International School

• The waste discharged by many factories contains acids.

• If these untreated factory waste are directly discharged into the water bodies, then the acids present in the factory waste kill the fishes and other aquatic organisms that live in water bodies.

• Factory waste should be treated with basic substances to neutralize the acids present in waste water before discharging them into water bodies.

Note: This presentation is a part of the E-Learning Program of Amarchand

Singhvi International School and is created only for educational purpose.

Compilation & presentation : Ms. Heemani Joshi

Web support & management : Mr. Deepak Chellani

Technical support : Mr. Shivam Gundecha

E-learning Program Co-ordination:

Mr. Prashant Chaturvedi

Produced by

Mr. Mridul Varma (Principal)Amarchand Singhvi International School

Parekh Parisar, Ward 7A, Gandhidham – Kutch

Gujarat 370201 India