Chapter 3

Matter and Energy

Assigned Problems

Recommended Exercises: 1-27 (odd)

Required Problems: 29-85 (odd) Cumulative Problems: 87-105 (odd)

Optional Highlight Problems: 107-113 (odd)

What Is Matter? Matter is any material that has mass and

occupies space Matter is made up of small particles

Atoms Molecules

Includes all things (living and nonliving) such as plants, soil, and rocks and any material we use such as water, wood, clothing, etc.

Classifications (of a sample of matter) is based on whether its shape and volume are definite or indefinite

Classifying Matter According to Its State Solid

Has a rigid, definite shape and definite volume Crystalline solids have a regular, internal long-range

order of atoms, ions, or molecules Amorphous solids have no long-range order of atoms,

ions, or molecules in their lattice structure Liquid

Has an indefinite shape and a definite volume. It will take the shape of the container it fills

Gas Has an indefinite shape and an indefinite volume. It will take the shape and completely fill the volume

of the container it fills Gases are compressible

Fig3_2(a) Solid (Ice) (b) Liquid (Water) (c) Gas (Steam)

Water is one of the few substances commonly found in all three physical states

Classifying Matter by Its Composition

Matter can also be classified in terms of its chemical composition

Pure Substances: Composed of only one atom or molecule Mixtures: Composed of two or more different atoms or molecules

combined in various proportions

Pure Substance Mixture

Matter

Pure Substances Matter that has a definite and constant

composition is a pure substance Composed of the same substance; no

variation 6 million pure substances have been isolated:

112 are elements, the rest are compounds The two classifications of pure substances:

Elements: e.g., a pure sample of copper or a pure sample of gold (one type of atom)

Compounds: e.g., example, a pure sample of water or a pure sample of sucrose (one type of molecule)

Pure Substances Elements

Substances which can not be broken down into simpler substances by chemical reactions

Fundamental substances Compounds

Two or more elements combined chemically in a definite and constant ratio

Can be broken down into simpler substances Most of matter is in the compound form

Pure Substances Compounds

Results from a chemical combination of two or more elements Can be broken down into elements by chemical processes Properties of the compound not related to the properties of

the elements that compose it Water is composed of hydrogen and oxygen gases

(combined in a 2:1 ratio)

Mixtures Something of variable composition Result from the physical combination of two

or more substances (elements or compounds)

Made up of two or more types of substances physically mixed

Each substance retains its identity because the substances are not chemically mixed

Mixtures of the same components can vary in composition

Mixtures Mixtures can be classified by the (visual)

uniformity of the mixture’s components Homogeneous mixture:

Same uniform composition throughout Not possible to see the two substances

present Heterogeneous mixture:

Composition is not uniform throughout the sample.

It contains visibly different parts or phases

Mixtures Homogenous mixtures

A sugar solution 14 karat gold, a mixture of copper and gold Air, a mixture of gases (oxygen, nitrogen)

Heterogeneous mixture Oil and vinegar Raisin cookies Sand

Pure substance e.g. copper (all elements are pure substances)

Compounds vs. Mixtures Compounds are not mixtures

Cannot be separated by a physical process Can be subdivided by a chemical process into two

or more simpler substances Simpler substances have different properties from

the compound

Mixtures Unlike compounds, mixtures can be separated by

a physical process Each substance in a mixture retain its own

individual properties

Classification of Matter

Elements Compounds

Pure Substances

HomogeneousMixture

HeterogeneousMixture

Pure Substances

Mixture

Matter

Chemical MethodsPhysical Methods

Physical and Chemical Properties

Various kinds of matter are differentiated by their properties Properties are the characteristics of a substance

used to identify and describe it Two general categories:

Physical Properties Chemical Properties

Properties can be: Directly observable (physical) The interaction of the matter with other

substances (chemical)

Physical and Chemical Properties:

Physical Properties A physical property is a characteristic of

a substance that can be observed without changing a substance into another substance Characteristics of matter that can be directly

observed or measured without changing its identity or composition

Color, odor, physical state, density, melting point, boiling point

Physical and Chemical Properties:

Chemical Properties A chemical property describes the way a substance

undergoes a change or resists change to form a new substance

Properties that matter exhibits as it undergoes changes in chemical composition:

Objects made from copper will turn green when exposed to moist air for long periods

Gold objects will resist change when exposed to moist air for long periods

Sodium metal will react strongly with water and produce hydrogen gas.

Classifying Properties

The boiling point of ethyl alcohol is 78 °C Physical property – describes an inherent

characteristic of alcohol, its boiling point Diamond is very hard

Physical property – describes inherent characteristic of diamond – hardness

Sugar ferments to form ethyl alcohol Chemical property – describes behavior

of sugar, ability to form a new substance(ethyl alcohol)

Physical and Chemical Changes Changes in matter are regular occurrences:

Food is cooked Paper is burned Iron rusts

Matter undergoes changes as a result of the application of energy

Changes in matter are also categorized as two types: Physical Chemical

Physical and Chemical Changes

A physical change is a process that alters the appearance of a substance but does not change its chemical identity or composition Folding aluminum foil sheets Crushing ice cubes

No new substance is formed Most common is a change of a substance’s

physical state The freezing of liquid water Evaporation of liquid water to steam

Physical and Chemical Changes

A chemical change is a process that changes the chemical composition of a substance Also called a chemical reaction (At least) one new substance is produced Wood burning, iron rusting, alka-seltzer

tablet reacting with water During a chemical change, the original

substance is converted into one or more new substances with different chemical and physical properties

Classifying Changes

Melting of snow Physical change – a change of state but

not a change in composition Burning of gasoline

Chemical change – combines with oxygen to form new compounds

Rusting of iron Chemical change – combines with

oxygen to form a new reddish-colored substance (ferric oxide)

Classifying Changes

Iron metal is melted Physical change – describes a state

change, but the material is still iron Iron combines with oxygen to form rust

Chemical change – describes how iron and oxygen combine to make a new substance, rust (ferric oxide)

Sugar ferments to form ethyl alcohol Chemical change – describes how sugar

forms a new substance (ethyl alcohol)

Conservation of Mass During a physical change: No new substance is

formed During a chemical change: At least one new

substance is formed Whether it is a physical or chemical change, the

amount of matter remains the same The law of conservation of mass states that the total

mass of materials present after a chemical reaction is the same as the total mass before the reaction

Matter is never created or destroyed

Energy Two major components of the universe:

Matter Energy

Energy is the capacity to do work or produce heat Electrical, radiant, mechanical, thermal, chemical,

nuclear Nearly all changes that matter undergoes involves

the release or absorption of energy Chemistry is the study of matter

The properties of different types of matter The way matter behaves when influenced by other

matter and/or energy

Energy Energy is the part of the universe that has the

ability to do work Energy can be converted from one form to another

but it is neither created nor destroyed (the law of conservation of energy)

Energy has two classifications Potential: Stored energy Kinetic: Motion energy

All physical changes and chemical changes involve energy changes

Energy Potential energy:

Determined by an objects position (or composition) Chemical energy (also potential energy) is stored in the bonds

contained within a molecule. It is released in a chemical reaction

Kinetic energy Energy that matter acquires due to motion Converted from the potential energy

All forms of energy can be quantified in the same units

Units of Energy The joule (J) is the SI unit of heat energy The calorie (cal) is an older unit used for

measuring heat energy (not an SI unit) The amount of energy needed to raise the

temperature of one gram of water by 1°C

The Cal is the unit of heat energy in nutrition

4.184 J = 1 cal 1 kcal = 1000 cal

1 Cal = 1000 cal = 1 kcal

Energy: Chemical and Physical Change

All physical changes and chemical changes involve energy changes which convert energy from one form to another

In terms of a chemical reaction the universe is divided into two parts:

The system (chemical reaction) The surroundings (everything else) The potential energy differences between the reactants and

products determine whether heat flows into or out of a chemical system

Whether a reaction is exothermic or endothermic depends on how the potential energy of the products compares to the PE of the reactants

Energy: Chemical and Physical Change

Chemical systems with high potential energy tend to change in order to lower their potential energy by the release of heat

Chemical reactions that release heat are called exothermic

Chemical systems with low potential energy tend to change in order to increase their potential energy by the absorption of heat

Chemical reactions that absorb heat are called endothermic

Temperature Temperature is a number related to the

average kinetic energy of the molecules of a substance

In a substance, the temperature: measures the hotness or coldness of an object measures the average molecular motions in a

system relates (directly) to the kinetic energy of the

molecules

Temperature Fahrenheit Scale, °F

Used in USA Water’s freezing point = 32°F, boiling point = 212°F

Celsius Scale, °C Used in science (USA) and everyday use in

most of the world Temperature unit larger than the Fahrenheit Water’s freezing point = 0°C, boiling point = 100°C

Temperature

Kelvin Scale, K SI Unit Used in science Temperature unit same size as Celsius Water’s freezing point = 273 K (0 ºC),

boiling point = 373 K (100 ºC) Absolute zero is the lowest temperature

theoretically possible No negative temperatures

Converting °C to °F

Units are different sizes Fahrenheit scale: 180 degree intervals

between freezing and boiling Celsius scale: 100 degree intervals

between freezing and boiling

180 F100 C

9 F5 C

1.8 F1 C

Fig2_9

32ºF 0ºC

100ºC Boiling point

Freezing point

212ºF

180Fahrenheitdegrees

100Celsiusdegrees

C 1

F 1.8

C 1

F 1.8

Converting °C to °F

To convert from °C to °F

Different values for the freezing points

Different size of the degree intervals in each scale

1.8 F1 C

TC T F 32

32 °F 0 °C

add 32 to the °F value

1.8 F1 C

TC FT 32

Converting °C to K Temperature units are the same size Differ only in the value assigned to

their reference points

25°C is room temperature, what is the equivalent temperature on the Kelvin scale?

K = °C + 273

25 ºC + 273 = 298 K25 ºC + 273 = 298 K25 ºC + 273 = 298 K

0 °C = 273 K

add 273 to the °C value

Example A cake is baked at 350 °F. What is

this in Centigrade/Celsius? In Kelvin?

1.8 F1 C

TC FT 32

1 C1.8 F

T F 32 T C

CT

32F350

F 1.8

C 1

TC 176.6667 C

176.7 273 =

K 449.7 K 450318 °F

Temperature Changes:Heat Capacity

Heat is the total amount of energy in a system It is function of the amount of motion (kinetic

energy) contained in molecules It is also a function of the potential energy of the

molecules It involves the exchange of thermal energy caused

by a temperature difference

Heat vs. Temperature Within a quantity of matter: Heat has units of Joules and temperature has units in

degrees Temperature relates only to kinetic energy within a

molecule Heat is the total amount of energy in a molecule: It

contains a kinetic and potential energy component Heat energy can be added or removed without a

change in temperature As heat energy increases the temperature increases

Temperature Changes: Heat Capacity

Heat energy is the form of energy most often released or required for chemical and physical changes

Every substance must absorb a different amount of heat to reach a certain temperature

Different substances respond differently when heat is applied

The amount of heat required to raise the temperature of a given quantity of a substance by 1 ºC is called its heat capacity

Temperature Changes: Specific Heat

If 4.184 J of heat is applied to: 1 g of water, its temperature is raised by 1 °C 1 g of gold, its temperature is raised by 32 °C Some substances requires large amounts of heat

to change their temperatures, and others require a small amount

The precise amount of heat that is required to cause a given amount of substance (in grams) to have a rise in temperature is called a substance’s “specific heat”

Specific Heat The amount of heat energy (q) needed to

raise 1 gram of a substance by 1 °C Specific to the substance The higher the specific heat value, the less its

temperature will change when it absorbs heat SH values given in table 3.4, page 71 Only for heating/cooling not for changes in state

C g

cal) (or J

Δt grams

heatSH

C g

cal

C g

J

Δ grams

)(heat

orT

qC

Specific Heat Expression with Calories and Joules

1 cal is the energy needed to heat 1 g of water 1 °C

1 cal is 4.184 JMake a conversion factor from the statements

C 11g

J 4.184

C 11g

cal 1water

C

Specific Heat Equation

q = heat C = specific heat (different for each substance) m = mass (g) ∆T = change in temperature (°C)

C)ΔT(m(g)Cg

Jq(J)

The rearrangement of the SH equation gives the expression called the “heat equation”

TgqC

Δ )(mass)( heat

joules in answer

TgCq Δ)(mass)heat (

C

Specific Heat Equation Energy (heat) required to change

the temperature of a substance depends on: The amount of substance being

heated (g) The temperature change (initial T

and final T in °C) The identity of the substance

Energy and T

The amount the temperature of an object increases depends on the amount of heat added (q) If you double the added heat energy (q), the

temperature will increase twice as much. When a substance absorbs energy, q is

positive, temperature increases When a substance loses energy, q is

negative, temperature decreases

Δt(g) mass(q)Heat C

2× 2×

Energy and Heat Capacity Calculations

Use same problem solving steps as before (Chapter 2) State the given and needed units Write the unit plan to convert the given unit to the final unit State the equalities and the conversion factors Set up the problem to cancel the units

Pepsi One™ contains 1 Calorie per can. How many joules is this?

4.184 J1 cal

4184 J1 Cal 1000 cal

1 Cal

1 Cal = 1000 cal 4.184 J = 1 cal

Energy and Heat Capacity Calculations

The 4184 J from the Pepsi One™ will heat how many grams of water from 0°C to boiling?

C100

mL 10g 10 J 4184J 4.184g1C1

Tqm

C

Energy and Heat Capacity Calculations

How many grams of water would reach boiling if the water started out at room temperature (25°C)?

25100

13.33 g 13.33 mL

4184 JJ 4.184

g 1C1 C75

T

qm

C

Energy and Heat Capacity Calculations

If 50.0 J of heat is applied to 10.0 g of iron, by how much will the temperature of the iron increase?

10.0 g11.11 C

50.0 J g C0.45 J

mq

T

C

ΔTmq C

Solve for ΔT

end