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MR. SURRETTE
VAN NUYS HIGH SCHOOL
CHAPTER 2: MATTER AND ENERGY
CLASS NOTES
MATTER
All objects in the universe are composed of matter. Matter provides weight and takes up space. Atoms
are the building blocks of matter.
STATES OF MATTER
Matter usually exists in three physical states: solid, liquid, and gas. Solids have a definite shape and a
definite volume. Liquids have an indefinite shape and a definite volume. Gases have an indefinite
shape and an indefinite volume.
STATES OF MATTER
Stars in outer space are a notable exception. They are composed mostly of a fourth state of matter called
plasma. Plasmas are ionized gases.
[Physical States of Matter handout]
SOLIDS
Solids can be crystalline or amorphous. Crystalline solids have a definite geometric pattern with
repeating units. Salts and minerals are good examples of crystalline solids.
SOLIDS
Amorphous solids have no definite shape nor geometric pattern. Glass, rocks, and rubber are examples
of amorphous solids.
SOLIDS
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
LIQUIDS
Liquids hold the shape of any container. The atoms or molecules in a liquid move in random patterns
because the intermolecular forces are too weak to hold the atoms or molecules in a solid form.
LIQUIDS
GASES
Gases hold the shape of any closed container. They can be expanded or compressed by the environment
(which affects pressure and temperature). They also have a low density.
GASES
MATTER CATEGORIES
Matter can be divided into two categories: pure substances and mixtures.
PURE SUBSTANCES
As the name suggests, pure substances are composed of only one type of substance. They can either be
elements or compounds. Elements are pure substances composed of a single type of atom like copper
wire.
PURE SUBSTANCES
Compounds break down into elements in fixed definite proportions. For example, water (H2O) always
breaks down into two parts hydrogen and one part oxygen.
[Matter handout]
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
MIXTURES
The opposite of pure substances, mixtures, cannot be broken down into two or more fixed definite
proportions. Mixtures can be homogeneous or heterogeneous.
HOMOGENEOUS MIXTURES
Homogeneous mixtures are two or more substances evenly mixed together. They often appear clear
like sugar or salt dissolved in water.
ALLOYS
Alloys are good examples of homogeneous mixtures. They are formed from pure metals evenly blended
together. For example, brass is an alloy made from copper and zinc.
HETEROGENEOUS MIXTURES
Heterogeneous mixtures are two or more substances unevenly mixed together. They often appear
cloudy and uneven like vegetable oil beading in vinegar.
PURE SUBSTANCES VERSUS MIXTURES
Example 1. Determine if the following substances are: pure elements, pure compounds,
homogeneous mixtures, or heterogeneous mixtures.
1a. argon (g)
A. Argon is atomic number 18 on the periodic table, which makes it an atom. Argon is a pure element.
1b. table sugar (s)
A. Table sugar is composed solely of sucrose. It is a pure compound.
1c. air (g)
A. Air is an uneven mixture of gases that varies all over Earth. It is a heterogeneous mixture.
1d. bronze alloy (s)
A. Bronze is an alloy, so it is a homogeneous mixture.
PROPERTIES
Properties are characteristics used to describe substances. For example, 100oC boiling point, and
odorless are both properties of water.
PHYSICAL PROPERTY
A physical property can be observed without changing the chemical formula of a substance. For
example, odorless is a physical property of water.
PHYSICAL CHANGE
A physical change is a characteristic that does not alter a substance's chemical composition. For
instance, water freezing into ice is a physical change.
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
CHEMICAL PROPERTY
A chemical property is a characteristic of a substance that cannot be observed without changing its
chemical formula. For example, water can react with hydronium ions (H3O+) to form acids.
CHEMICAL CHANGE
Chemical changes alter the initial composition of a substance. For example, the reaction:
2 H2(g) + O2(g)  2 H2O(g) is a chemical change.
PHYSICAL VERSUS CHEMICAL CHANGE
Example 2. Indicate whether each of these is a physical or a chemical change:
2a. Snow melting.
A. physical change
2b. Liquid gasoline vaporizes into air.
A. physical change
2c. Gasoline burns in a car engine.
A. chemical change
ENERGY
Energy makes matter move. Forms of energy include: kinetic, potential, electrical, chemical,
mechanical, nuclear, and heat.
UNITS OF ENERGY
Small amounts of energy are often measured in calories or joules. A calorie (c) is the energy required to
raise the temperature of one gram water by 1o C.
UNITS OF ENERGY
A joule (J) joule is the energy needed to move a one Newton mass (about ¼ English pounds) over the
distance of a meter. It is also smaller than a calorie.
UNITS OF ENERGY
When larger units are required, kilocalories and kilowatt-hours are sometimes used. A kilocalorie (C) =
1000 calories. (Food calories are actually kilocalories. A typical candy bar may contain 200 Calories =
200,000 calories).
UNITS OF ENERGY
A kilowatt-hour (kwh) = 3.6 x 106 joules. Power companies often compute utility bills using kilowatthours.
ENERGY CONVERSIONS
In certain types of problems, it becomes necessary to convert from one unit of energy to another.
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
ENERGY CONVERSIONS
Some common energy conversion factors are:
1 calorie = 4.18 joules
1 Calorie = 1 kcal = 1000 calories
1 kwh = 3.6 x 106 joules
Example 3. Convert 135 J into Calories.
3A.
(1) 135 J x 1 c
x 1C
------------------ = 0.032265774 C
4.184 J
1000 c
(2) 3.2265774 x 10-2 C
(3) 3.23 x 10-2 C
Example 4. Convert 275 joules into kwh.
4A.
(1) 275 J x
1 kwh
------------- = 7.6388889 x 10-5 kwh
3.6 x 106 J
(2) 7.64 x 10-5 kwh
CHANGES IN PHYSICAL STATE
Almost everything can exist as a solid, liquid, or gas. For example, H2O can become ice, water, or
vapor depending on its temperature.
WATER TEMPERATURE-ENERGY GRAPH
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
SPECIFIC HEAT CAPACITY
If a substance is heated without a change in state, the amount of heat required to change the temperature
of 1 gram by 1o Celsius is called the specific heat capacity.
MOLAR HEAT CAPACITY
Chemists often use a unit of measurement called a mole. A mole is equal to 6.022 x 1023 atoms or
molecules. Molar heat capacity is the amount of heat needed to raise the temperature of 1 mole of a
substance by 1o C.
Example 5. Calculate the calories required to heat one kilogram of aluminum from 10oC to 70oC.
5A.
(1) From the Heat Capacities data table: Al = 0.213 cal/deg/gm
(2) 1000 g Al
(0.213 cal/deg)
------------------ = 213 cal/deg
1g
(3) 60oC (213 calories)
-------------- = 12,780 calories
1o C
HEAT OF TRANSFORMATION
A considerable amount of energy is required to transform a low energy state into a higher energy state.
Phase changes like melting a solid into a liquid, or freezing a liquid to a solid are good examples.
Example 6. Calculate the calories required to change 100 grams of ice at - 40oC to water at 20oC.
6A.
Ice: - 40oC  0oC
(1) From the Heat Capacities data table: H2O(solid) = 0.485 cal/deg/gm
(2) 100 g Ice (0.485 cal/deg)
------------------ = 48.5 cal/deg
1g
(3) 40oC (48.5 calories)
------------------ = 1940 calories
1oC
Solid  Liquid:
(4) From the Heats of Transformation data table: H20 heat of fusion = 79.8 cal/gm
(5) 100 g H2O (79.8 calories)
----------------- = 7980 calories
1g
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CHEMISTRY
MR. SURRETTE
VAN NUYS HIGH SCHOOL
6A. (continued...)
Water: 0oC  20oC
(6) From the Heat Capacities data table: H2O(liquid) = 1.000 cal/deg/gm
(7) 100 g Water (1.000 cal/deg)
------------------- = 100 cal/deg
1g
(8) 20oC (100 calories)
----------------- = 2000 calories
1oC
(9) Total calories: 1940 calories + 7980 calories + 2000 calories
(10) Total calories = 10,120 calories
TEMPERATURE
Temperature measures the average kinetic energy of atoms and molecules in a substance. The higher a
substance’s temperature, the faster its atoms and molecules move.
PRESSURE
Pressure measures the amount of force on a surface by an object or fluid. Pressure is usually measured
in atmospheres.
PHASE DIAGRAMS
In laboratory experiments, temperature and pressure can be varied or held constant. Phase diagrams
assign these variables to axes to form a plot that describes the physical condition of each point on the
graph.
PHASE DIAGRAM FOR WATER
[FIGURE 7-1, PAGE 66]
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