Web viewIntroduction, Problem, ... Then use a prefix for the number of water molecules attached and...

Chemistry 20 Review - Introduction and Quick Review

Welcome to Classroom

The goal in this room is …. SUCCESS !!

As a team (student, parent, teacher) we will all work towards the achievement of this goal !

The expectations set out are there to help ensure that students can realistically reach this goal

If you have any questions or concerns, make an appointment with me and we can discuss

Do you have the skills ?

Let’s go over a few things that you need to make sure you have before you start this course

Scientific Knowledge

Scientific Knowledge is built on the results of countless ___________________ conducted by many investigators.

In order to find answers to questions in science, the scientific process must be _______________, __________________ and _____________________.

A useful, __________________ scientific investigation generally has all of the following parts

Introduction, Problem, Design, Data collection, Analysis and Conclusion.

** We will be discuss designing and reporting scientific investigations more later on **

Science deals with two types of knowledge:

Empirical Knowledge – this type of knowledge is ____________________________. (facts)

Theoretical Knowledge – this type of knowledge is __________________________. (interpretations and theories)

Empirical (directly observable ) knowledge is considered more certain than interpretations or theoretical explanations.

Scientific Knowledge

Observations Versus Interpretations in Science

An observation is any report from your 5 senses. It does not involve an explanation. An observation can also involve measurements. Such an observation is a _________________________ one, as opposed to a ______________________________ one (no measurements).

An interpretation is an attempt to figure out what has been observed. Here are some examples designed to help you distinguish between them.


When doing labs, it is important not to confuse observations with interpretations. If you are asked to observe, you should not identify gases. “Hydrogen gas was produced when zinc was added to acid” is not an observation. What you see is the liquid getting cloudy with bubbles rising from the area surrounding the metal. The latter is what you should be reporting as an observation. Later if you collect the gas and it has hydrogen’s characteristic property, then it will be time to conclude that the bubbles contained hydrogen gas.

Precision, Error and Accuracy

A major component of the scientific inquiry process is the comparison of experimental results with predicted or accepted theoretical values.

All measurements have some degree of ____________________________.

Uncertainty, often referred to as error , is not the result of a mistake necessarily, but can be caused by _____________________________ of the equipment or experimenter.

_________________________ – describes the exactness and repeatability of a value or set of values.

_________________________ – describes the degree to which the result of an experiment or calculation approximates the true value.

Percent Difference & Percent Yield

____________________________ – determines how precise a set of measurements is. Compares experimental values to constants or theoretical values. (acceptable values for high school labs are ±10%.)

______________________________ – determines how close an actual(experimental) yield is to the predicted or theoretical value. (acceptable values for high school labs are >90%.)


Significant Digits

Examples

How many significant digits does each number have ??

1. 4568

2. 3.49

3. 0.0000862

4. 0.05009

5. 50.17

Significant Digits – Calculations Examples

How many significant digits would each answer have ??

Don’t forget to round properly

1. 5.3 + 7.62 – 3.298 =

2. 4.88 / 2.3 x 1.16 =

Scientific Notation

Used to _____________________________ large numbers (and to clarify the number of significant digits), when reporting them and doing calculations.

MAKE SURE YOU CAN PUT THIS INTO YOUR CALCULATOR ACCURATELY!!!

Rules for Scientific Notation

If you want to make an exponent larger move the decimal to the left

If you want to make an exponent smaller move the decimal to the right

Scientific Notation Examples


1. 0.000000000523

2. 5110300000000000

Complete the following

1. 6.7 x 10 -4 + 3.3 x 10 -3 =

2. 4.6 x 10 7 - 2.1 x 10 5 =

3. (8.9 x 10 2) x (5.2 x 10 4 ) =

4. (4.4 x 10 8) / (1.2 x 10 3) =

SI Units

The International System of Units, ___________________, from the French Name, systéme international d’unites.

The measurement and communication system used ____________________________ by scientists

Physical quantities are ultimately expressed in terms of 7 fundamental SI units, called __________________All other quantities are derived from these units

SI Units – Base units Universality

SI Units – Prefixes Convenience

With the exception of centi-, we use prefixes that change by multiples of 1000


Tables and Graphs

Both tables and graphs are used to summarize information and to illustrate __________________ or _________________________.

It is important to prepare them ___________________________, following accepted conventions, in order to best communicate the information.

Tables

1. All tables must have descriptive titles that mention both the manipulated and responding variables.

2. The row or column containing the manipulated variable precedes the responding

3. Headings of rows or columns are labelled with the units in parentheses where applicable and not included in the body of the table.

Graphs

1. Descriptive title (manipulated & responding variables are mentioned)

2. Labeled axes with units in parentheses

1. X-axis has the manipulated variable

2. Y-axis has the responding

3. Use appropriate scales, with equal increments, on the axes so the graph takes up at least ½ of the paper

4. Use a pen for data points

5. Draw, in pencil, a line of best fit if the data appears in to be in a straight line, if not use a smooth curve to connect the points


Interpolation

Finding a value between a set of data points

Extrapolation

Finding a value past a set of data points (dotted line)

Manipulating Formulas

Opposite Operation

What is done to one side must be done to the other.


Now down to the Chemistry Let’s get ready for Unit 1

Remember …

Chemistry is the physical science that deals with the composition, properties and changes in matter.

Classifying Matter

Matter: anything that has mass and takes up space.

Chemists can classify matter as solid, liquid, or gas. But there are other ways to classify matter, as well — such as pure substances and mixtures. Classification is one of the basic processes in science. All matter can be classified as either a pure substance or a mixture

PURE SUBSTANCES:

A pure substance has a definite and constant composition — like water or sulfur. A pure substance can be either an element or a compound, but the composition of a pure substance doesn’t vary.

Pure substances have definite properties that are always the same (e.g. mp, bp, density, etc). You cannot distinguish a solution from a pure substance by looking at it, as they appear homogenous. There are two types of pure substances:

Elements:

are pure substances that cannot be broken down into simpler substances. They are the smallest particle that is the element. Empirical

They are composed of one type of atom (Theoretical), and are the building blocks of all compounds.

Each element has its own symbol, the first letter always being capitalized, and the second letter being lower case. Currently there are 118 different elements

*** Every element has very unique properties (i.e. (s), (l), (g), reactivity, density etc.).

Compounds:

are pure substances that contain two or more elements in definite proportions (fixed ratios) Theoretical

Compounds can be broken down into the elements they are made of. Empirical

Even though there are only 118 elements, there are millions of compound possibilities that can be formed from these elements.


Mixtures:

Mixtures are physical combinations of pure substances that have no definite or constant composition — the composition of a mixture varies according to who prepares the mixture.

Although chemists have a difficult time separating compounds into their specific elements, the different parts of a mixture can be easily separated by physical means, such as filtration or evaporation

Heterogeneous Mixtures:

aka Mechanical Mixtures have visible different parts (e.g. concrete, salt & pepper, soil, granola, chocolate chip cookies, etc.).

Homogeneous Mixtures

aka solutions are type of mixture where you only see one part. It appears to be one substance (e.g. soft drinks, clear tea, Kool-Aide, salt water, metal alloys, etc.) and cannot be easily distinguished from a pure substance without further testing.

Periodic Table

Dmitri Mendeleev created the periodic table in 1869

Periodic Law

Chemical & physical properties of elements repeat themselves in regular intervals when elements are arranged in order of increase atomic #

How its put together

Family (or Group): are the vertical columns on the periodic table numbered 1-18. Elements within a group have similar chemical properties to each other.

Periods: are the horizontal rows on the periodic table numbered 1-7. As you move left to right, you see an increase in the number of protons. On the far left we start with metals, and as we move farther to the right we end up in non-metals. Reactivity in metals usually decreases as we move to the right.

Atoms:

Atoms are the basic units of matter and the defining structure of elements. Atoms are made up of three particles: protons, neutrons and electrons.

Electrons are extremely lightweight and exist in a cloud orbiting the nucleus. The electron cloud has a radius 10,000 times greater than the nucleus


Atomic number:

represents the number of protons an atom contains. The atomic number is found in the top left corner of each element.

Atomic Mass:

is the mass of each element. This mass is made up of the number of protons plus the number of neutrons found in an atom (remember electrons have very little mass).

Isotopes:

Atoms of the same element that have a different number of neutrons.

IONS

Are atoms that have either lost or gained electrons in order to have a full outer shell of electrons.

Metals will lose electrons to become positively charged ions(CATIONS).

Non-metals will gain electrons to become negatively charged ions (ANIONS).

*** It is important to remember that electrons are negatively charged, so if an atoms gain electrons the charge becomes negative.

Bohr Model/Energy Level Diagram

Write # of protons and neutrons in the nucleus (or under a line)

Draw circles (or lines) to represent electron shells

Draw on Electrons

Remember:

2 – 8 – 8- 16

If there are more than 4 electrons there will be pairs

Bohr Model/Energy Level Diagram Examples


Diatomic Elements

Always in pairs. KNOW THESE!!!!

H2, N2, O2, F2, Cl2, Br2, I2

Polyatomic Elements

S8 and P4

Know these too! *This is SUPER important for writing and balancing chemical reaction equations*

Compounds

Ionic & Molecular Compound properties

Naming Ionic compounds

Naming Molecular compounds

Ionic Compounds

Ionic compounds are pure substances formed from a metal and a non-metal.

Ex. NaCl

All ionic compounds are solids at room temperature (High mp. And bp.)

When an ionic compound is dissolved in water, it will conduct electricity (because of the presence of charged particles)

Ionic Bond formed by the transfer of electrons creating ions that are attracted to each other

Example: Na + and Cl - NaCl

Molecular Compounds

Molecular compound- when two non-metals combine and electrons are shared

They can be solids, liquids or gases at room temperature

They tend to be insulators (poor conductors of electricity) even in solutions, because there are no IONS in MC

Have low melting and boiling points


Names and Formulas

The chemical formula of an element or compound indicates which elements and how much of each one is present in a compound.

Chemical nomenclature is the systematic method of naming substances

Ex. table salt has the chemical name sodium chloride and its formula is NaCl.

International Union of Pure and Applied Chemistry

IUPAC for short

The governing body for scientific communication which specifies rules for chemical names and symbols (**Remember the universality of science )

These are the rules we follow for naming all elements and compounds.

Naming Ionic Compounds

When you have a chemical formula

LiF(s) MgCl2 (s) FeS(s) Fe2S3 (s)

1. Identify the metal first, and name

Check the periodic table to see if the metal is multivalent (more than one ion charge)

If not move on, if it is use subscripts to determine which charge and use roman numerals between the names

2. Name the non-metal second

The name of the non-metal changes its ending to –ide

**In high school chemistry, we name BINARY COMPOUNDS, so there is only one cation and one anion**

When you have a chemical formula

LiF(s)

MgCl2 (s)

FeS(s)

Fe2S3 (s)


Polyatomic Ions

Polyatomic ions are groups of atoms acting as one. Ex. Carbon and oxygen can act as one - CO3

2-

Polyatomic ions are composed of two or more elements covalently bonded with an overall negative or positive charge.

These are found on your periodic table.

This table is found on the back of your periodic table, and is used as a reference for you to help identify them in the compounds.

Polyatomic Ions - Examples

NaCH3COO (s) –

K2Cr2O7 (s) –

MnHPO4 (s) –

Steps to writing formulas

1. Write the metal ION symbol with its ion charge. Next to it write the non-metal elements symbol with its ion charge.

Ex. Ca2+ Cl-

2. Balance the ION charges to ZERO.

There must be two chlorine atoms each with an ion charge of 1- to balance the 2+ ion charge of one calcium atom.

Ex. Cl- Cl- Ca2+

Steps to writing formulas

3. Write down the formula by indicating how many atoms of each element are in it. Then write the state in parentheses.

Ex. CaCl2 (s)

After a chemical formula a subscript in parentheses indicates the compounds physical state.

Ex. (g) = gas, (l) = liquid, (s) = solid (aq) = aqueous (dissolved in water)

Now you Try


Beryllium nitrate Copper(I)sulfate

Sodium hydroxide Chromium(II)phosphate

Ionic Hydrates

Some ionic compounds exist as hydrates

This means that the compounds have water molecules attached to them.

To name them

1. Identify and name the ionic compound

2. Then use a prefix for the number of water molecules attached and put it in front of the word hydrate.

Example

BaSO4 • 4H2O (s)

Naming Molecular Compounds

1. The first element in the compound uses the element name

2. The second element has the suffix -ide

3. When there is more than one atom in the formula, a prefix is used which specifies the number of atoms

4. However, when the first element has only one atom the prefix mono is not used.

***Many molecular compounds are known by their common names Ex. water, ammonia

Example

CO2 =

N2O =

CCl4 =

Writing Formulas for Molecular Compounds


They differ from ionic compounds because no ions are present

Remember!!

A few elements are diatomic meaning that they are always found in the form O2, N2, H2, F2, Cl2, Br2, I2, and P4, S8 when written alone

Writing Formulas for Molecular Compounds

P5O10 =

CO =

CH4 =

Naming Acids and Bases

Acids – are aqueous hydrogen compounds that make blue litmus paper turn red and are generally written with hydrogen appearing first in the formula

Ex. HCl

Ex. H2SO4

**** acids containing –COOH, the H is placed at the end of the formula

Ex. CH3COOH(s) acetic acid

Ex. C6H5COOH(s) benzoic acid

1. If the anion name ends in “ide” the acid name is hydro__________ic acid

Eg. HCl

Eg. H2S

2. If the anion name ends in “ate” the acid name is ________ic acid

Eg. HNO3(aq)

Eg. H2SO4

3. If the anion name ends in “ite” the acid name is ________ous acid

Eg. H2SO3

Bases


aqueous ionic hydroxides form electrically conductive solutions and turn red litmus paper blue.

Eg. KOH –

Weak bases – react with water to form solutions containing hydroxide

Eg. NH3 –

Practice Problems

TEXTBOOK

Pg 40 Q 20-22, 24-25

Types of Chemical Reactions

5 Types


Formation

Decomposition

Combustion

Single Replacement

Double Replacement

Formation Reactions (synthesis)

2 elements combine to form a compound

X + Y XY

Ex. Na(s) + Cl2(g) NaCl(s)

Decomposition Reactions

one compound breaks down into two or more simpler compounds or elements (opposite of formation reactions)

XY X + Y

Ex. 2 H2O(l) 2H2(g) + O2(g)

(electrolysis of H2O)

Hydrocarbon Combustion

A hydrocarbon (CnHn) (i.e. oil, fuel, natural gas) reacts with oxygen gas to form carbon dioxide gas and water vapor and heat.

CnHx + O2(g) = CO2(g) + H2O(g)

Ex. CH4(g) + O2(g) CO2(g) + H2O(g) + thermal energy

Single replacement reactions replace one element from a compound with another element.


A compound and an element react, and the element switches places with part of the original compound.

AB + C AC + B

Double replacement reactions swap elements between 2 compounds that react together to form two new compounds.

Two compounds react, with elements switching places between the original compounds.

AB + CD AD + BC

Example: MgO + CaS

Summary

Solubility

A SOLUTION is a homogeneous mixture of a SOLUTE (substance dissolved) and a SOLVENT (substance dissolving, usually a liquid).

SOLUBILITY is the maximum amount of a substance that can be dissolved at a specific temperature.

Balancing Chemical Reaction Equations


A balanced chemical reaction is one in which the total number of each kind of atom or ion in the reactants is equal to the total number of the same kind of atom or ion in the products.

This is the LAW OF CONSERVATION OF MASS

Balancing Equations

Need equal # of each element on both sides of the reaction

Steps for balancing chemical Equations

Step #1 – write the chemical formula for each reactant and product including the state of matter

Step #2- balance the atom or ion using coefficients. Make sure to use the lowest common multiple

Step #3 Check your balancing

Chemical Amount


A mole is the unit of chemical amount of a substance with the number of entities corresponding to Avogadro’s number (6.02 x 1023)

N2(g) + 3H2(g) → 2NH3(g)

One mole of nitrogen gas and three moles of hydrogen gas react to form two moles of ammonia gas

Molar mass (M)- the mass of one mole of the substance. Units are g/mol

How to calculate molar mass:

1. Write the correct chemical formula

2. Identify the number of atoms of each element present in the formula

3. The molar mass is the sum of the number of atoms multiplied by the atomic molar mass of each element.

Calculations:

3 types of problems that you have to be able to do:

calculate M (molar mass) – you can do that now! (Remember: Periodic Table)

calculate the number of moles of a substance (given the mass in g)

calculate the mass of a substance (given the number of moles)

The Mole – extra on wiki


Practice Problems

Textbook

Pg 66 Q 7-9

Pg 69 Q 18-27

pH, pOH & [H3O+], [OH-]

The number of digits following the decimal point in a pH or pOH value is equal to the number of significant digits in the corresponding hydronium or hydroxide concentration.

For both pH and pOH, an inverse relationship exist between the ion concentration and the pH or pOH. The greater the hydronium ion concentration, the lower the pH is.

Net Ionic Equations


Stoichiometry

Limiting and Excess Reagents

When no further changes appear to be occurring, we conclude that the reaction has gone to completion.

A limiting reagent is the reactant whose entities are completely consumed in a reaction, meaning the reaction stops.

In order to make sure this happens, more of the other reactant must be present than is required

An excess reagent is the reactant whose entities are present in surplus amounts, so that some remain after the reaction ends..

Practice

How much precipitate is produced from a reaction of 10.0g of Silver nitrate and 10.0g of zinc chloride ?

Practice


In an experiment, a 10.00 mL sample of sulfuric acid solution reacts completely with 15.9 mL of 0.150 mol/L potassium hydroxide. Calculate the amount concentration of the sulfuric acid.

Practice Problems

Textbook

Pg 66 Q 7-9

Pg 69 Q 18-27

Pg 350 Q 21-26, 31

Web viewIntroduction, Problem, ... Then use a prefix for the number of water molecules attached and...

Documents

Transcript of Web viewIntroduction, Problem, ... Then use a prefix for the number of water molecules attached and...