Unit 2 - Chemistry - · PDF fileThe 4 Principles of the Particle Theory of Matter •All...

Chapter 2

Elements & Compounds

2.1 Models of Matter: The

Particle Theory

• 2000 years ago a philosopher named

Democritus suggested that matter was made

up of tiny particles too small to be seen.

• If you keep cutting a substance into smaller

pieces, you will eventually come to the

smallest possible particles - the building

blocks of matter. Think of Lego pieces.

The 4 Principles of the Particle

Theory of Matter

• All matter is made up of tiny particles.

• All particles of one substance are the same. Different substances are made of different particles.

• The particles are always moving. The more energy the particles have, the faster they move.

• There are attractive forces between the particles. These forces are stronger when the particles are closer together.

Matter Concept Map

Pure Substances and Mixtures

• There are two categories of substances:

– pure substances

– mixtures

Pure Substances

• Contains only one kind of particle.

• Examples:

– aluminum foil only contains aluminum particles

– sugar contains only sugar particles.

Mixture

• Contains at least two different pure

substances.

• Examples:

– Hot chocolate

– Oreo cookie

How to Classify Mixtures

• When two pure substances are mixed

together, they may mix smoothly or

unevenly.

• If the substances mix well with one another,

the mixture is called a solution.

• If the particles don’t mix well together then

we have a heterogeneous mixture.

Classify the Following

• Salt and water

– solution

• Pizza

– heterogeneous mixture

• Garbage

– heterogeneous mixture

• Air

– solution

Elements and Compounds

• Elements are pure substances that cannot be

broken down into simpler substances.

– Elements are the building blocks of matter!!!

• Compounds are pure substances that contain

two or more different elements in a fixed

proportion. Example: water is H2O.

Atoms and Elements

• Scientists now call the particles in the

particle theory atoms.

• Each element is made of only one kind of

atom.

• How many kinds of atoms are there?

– Since there are over 100 kinds of elements in

the periodic table, there are over 100 kinds of

atoms.

Guess the Molecule

• I have 2 hydrogen atoms

• I have 1 oxygen atom

• I am water

Guess the Molecule


• I have 2 oxygen atoms

• I have 7 carbon atoms

• I have 4 nitrogen atoms

• I am desired in the morning but

avoid me in the evening

• Cola drinks have me in

common

• I am what makes coffee special

• I am caffeine

Molecules

• Atoms join together in combinations.

• When two or more atoms join together, a molecule

is formed.

• Molecules can contain two atoms or thousands of

atoms.

– Water molecules have 2 hydrogen atoms and 1 oxygen

atom

– Methane gas molecules have one carbon atom and 4

hydrogen atoms

– Acetic acid(vinegar) has 2 C, 2 O and 4 H

Guess the Molecule




• Everybody needs me

• I will help keep colds away

• You can get me by eating

oranges

• I am vitamin C

Guess the Molecule




• I am used quite often by

teachers, usually in pairs

• I am white in color

• You need water when you use

me

• I will make you feel better

• I am aspirin

Assignment

• Complete “2.1 Worksheet” on classifying

materials (it’s in the shared file). Copy the

document into your science folder and then

answer the questions on loose-leaf. Put

your name and date on the sheet and hand in

to teacher.

2.7 Chemical Symbols and Formulas

• All elements on the periodic table have

symbols that are recognized world wide.

• It does not matter which country or

language, the element Iron is always

identified by “Fe” and Oxygen is “O”.

• The names are not always the same but the

symbols are. Fe is iron in Canada, fer in

France and Fier in Romania.

Chemical Symbols and Formulas • Today, a common set of symbols for elements is

accepted around the world.

• A chemical symbol is an abbreviation of the name of an element.

• The names and symbols for elements come from many sources.

– Hydrogen comes from the Greek word for “water-

former.”

– Mercury was named after a Roman God but the

symbol, Hg, comes from the Latin word

Hydrargyrum for “liquid silver.”

Chemical Symbols and Formulas

• Single symbols are used to represent elements.

• Combinations of symbols are used to represent

compounds. These combinations are called

chemical formulas.

• The chemical formula indicates which elements

are present and in what ratio.

Chemical Formulas - examples

• Calcium Carbonate(chalk) - CaCO3

• Sodium Chloride(salt) - NaCl

• Acetylsalicylic acid (aspirin) - C9H8O4

• Acetic acid (vinegar) - C2H4O2

• Special notes:

– Each symbol in a formula represents an element.

– If only one atom of an element is present in the

compound, no subscript is used.

– If more than one atom of an element is used, then the

symbol is followed by a number indicating how many

atoms are used. This is called the subscript.

Homework

• Answer questions 1,2,3,4,5 on page 59.

2.8 Atoms, Molecules, and the

Atmosphere

• Every person on the planet earth needs air

to breathe. But, have you ever wondered

what air is made up of?

• Take a minute and write down what you

think makes up air.

• Now, write down the corresponding

percentages for each component of air.

Atoms, Molecules, and the

Atmosphere

• Here are the actual components of air:

– Oxygen

– Nitrogen

– Argon (Ar)

– Carbon Dioxide (CO2)

Oxygen

• Atoms of oxygen can combine to form two

different molecules:

• O2 is oxygen gas. It makes up 21% of air.

• and O3 is ozone. It is formed naturally in the

upper layers of the atmosphere.

• Ozone is important since it absorbs most of the

ultraviolet radiation from the Sun.

• The ozone layer is being destroyed by CFCs or

chlorofluorocarbons.

Nitrogen

• Nitrogen makes up 78.02% of the

atmosphere.

• It is not very reactive, which means we can

inhale it without causing chemical changes

in our lungs.

• We do not want to inhale nitrogen dioxide

since it is a very toxic gas.

Argon

• Argon gas is completely harmless.

• Almost all of the argon in the atmosphere

has leaked out from inside the Earth.

• Argon is used for filling electric light bulbs

and fluorescent tubes.

• Argon and other gases make up 0.94% of

the atmosphere.

Carbon Dioxide CO2

• When fossil fuels burn, the two main

products are carbon dioxide and water.

• Carbon dioxide is used by plants.

• Carbon dioxide makes up 0.03% of the

atmosphere.

Carbon Monoxide (CO)

• Produced during combustion when there is a lack

of oxygen. For example, if you use a propane

barbecue indoors, or if you run an automobile

inside a closed garage.

• The CO molecule is similar to the oxygen

molecule in that when carbon monoxide enters

the lungs, the body’s red blood cells treats it the

same as oxygen and carries it throughout the

body. The cells of the body are then starved of

the oxygen they need and you could die.

Answering Questions about

Various Molecules

By looking at the chemical formula of a molecule

we can answer a variety of questions such as:

• Which elements are required to construct the molecule?

• How many atoms, in total, are required to construct the

molecule?

• How many atoms, of each element, are required to

construct the molecule?

• What is the ratio of each type of atom in the molecule?

• What is the mass of each molecule?

An Example

C9H8O4 or Aspirin


C = Carbon H = Hydrogen O = Oxygen


molecule?

9 + 8 + 4 = 21 total atoms in one molecule of Aspirin



9 Carbon, 8 Hydrogen and 4 Oxygen atoms are required

to construct one molecule of Aspirin.

An Example

C9H8O4 or Aspirin


9/21 is Carbon 8/21 is Hydrogen 4/21 is Oxygen


Mass of one molecule of aspirin is calculated as follows:

(atomic mass C) x 9 (12) x 9 108

(atomic mass H) x 8 (1) x 8 8

+ (atomic mass O) x 4 (16) x 4 64

180

The atomic mass of one molecule of Aspirin is 180.

An Example - You do it!

Theobromine (Chocolate) - C7H8N4O2



molecule?





An Example - You do it!



C = Carbon H = Hydrogen N = Nitrogen O = Oxygen


molecule?

7 + 8 + 4 + 2 = 21 total atoms in one molecule of Chocolate



7 Carbon, 8 Hydrogen, 4 Nitrogen and 2 Oxygen atoms are

required to construct one molecule of Chocolate.

An Example



7/21 is Carbon 8/21 is Hydrogen 4/21 is Nitrogen and 2/21 is Oxygen


Mass of one molecule of chocolate is calculated as follows:

(atomic mass C) x 7 (12) x 7 84

(atomic mass H) x 8 (1) x 8 8

(atomic mass N) x 4 (14) x 4 56

+ (atomic mass O) x 2 (16) x 2 32

180

The atomic mass of one molecule of chocolate is 180.

Assignment

• Do the “Counting Atoms” worksheet that’s

in the shared file

– For the molecules containing calcium,

aluminum and chromium calculate the atomic

mass also.

• Hand in the worksheet and then move on.

• Questions 1, 2 and 4 on page 61

2.7 Counting Atoms

Rules for Counting Atoms 1. The symbol of an element represents one atom of

that element. Example: Na – 1 atom of Sodium 2. The subscript number indicates the number of

atoms for that element. Examples: H2 – 2 atoms of Hydrogen H2SO4 – 2 atoms of Hydrogen 1 atom of Sulfur 4 atoms of Oxygen

3. A subscript outside a bracket multiplies to all the elements inside the brackets.

Examples: Mg3(PO4)2 – 3 atoms of Mg 1×2 = 2 atoms of P 4×2 = 8 atoms of O Ca4(SO4)3 - 4 atoms of Ca 1×3 = 3 atoms of S 4×3 = 12 atoms of O

4. A coefficient is a number written in front of a chemical formula. The coefficient indicates the number of molecules of that compound. A coefficient multiplies the number of atoms of each element in the formula.

Examples: 2H2O = H2O + H2O = 4 atoms of H and 2 atoms of O 3CuSO4 = CuSO4 + CuSO4 + CuSO4 = 3 atoms of Cu 3 atoms of S 12 atoms of O 4Pb(NO3)2 = Pb(NO3)2 + Pb(NO3)2 + Pb(NO3)2 + Pb(NO3)2 = 4 atoms of Pb 1×2×4 = 8 atoms of N 3×2×*4 = 24 atoms of O

2.10 Names & Formulas for

Compounds

• We’ve been looking at chemical formulas

and calculating numbers of atoms, but how

do you know how to put these elements

together to form compounds?

• There are 5 basic rules that you follow to

write out a chemical formula:

How Elements Combine

• 1: metals combine with nonmetals a lot of the time

• 2: write the name of the metal element first and then the name of the nonmetal

• 3: change the ending on the nonmetal to “ide”

• 4: look up the “combining capacity” of the elements involved

• 5: atoms will combine so that each element is at full capacity

Combining Capacity

• Combining capacity is basically how many

connections an atom can make to other

atoms

• For example if the metal sodium joins with

a nonmetal such as bromine, they each have

a combining capacity of 1 so the compound

created would be NaBr (1 atom of each

because each element can make one bond)

combining capacity of some metals

• Aluminum

• Barium

• Calcium

• Magnesium

• Potassium

• Silver

• Sodium

• zinc

• 3

• 2

• 2

• 2

• 1

• 1

• 1

• 2

combining capacity of some

nonmetals

• Bromine

• Chlorine

• Fluorine

• Iodine

• Oxygen

• sulfur

• 1 (bromide)

• 1 (chloride)

• 1(fluoride)

• 1 (iodide)

• 2 (oxide)

• 2 (sulfide)

Assignment

• Look over the example of ball & hook

diagrams on p. 65 of the text

– Start ball & hook diagrams by drawing the

metal first and it’s hooks, then attach the

nonmetal element to it

– Using these examples and info. in your notes

and text, do the following questions

– 3 & 4 p. 65

Assignment

• Do “Naming Ionic Compounds” worksheet

(it’s in the shared file and notes are provided

on the sheet)

Chapter 2 Review

Questions • P. 76 & 77 # 2, 3, 4, 8, 10 and

11

• Study chapter 2 notes and

prepare for quiz tomorrow!

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Unit 2 - Chemistry - · PDF fileThe 4 Principles of the Particle Theory of Matter •All...

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