Chapter 3

Matter, Changes and Energy

2

Formulating some questions

What are the most basic forms of matter?

What are the criteria that allow us to

distinguish one substance from another?

How do we describe mixtures of

substances?

How does energy relate to changes in

matter?

Chapter 3 Objectives

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OBJECTIVES

Section You Should be able to… Examples Exercises

Chapter Problems

3-1 List and define several

properties of matter and

distinguish them as

physical or chemical.

1a, 1b, 1c 4, 5, 6, 9, 11

3-2 Perform calculations

involving the density of

liquids and solids.

3-1, 3-2, 3-3,

3-4

2a, 2b, 2c 12, 14, 16, 20,

22, 24, 28, 29

3-3 Describe the differences

in properties between a

pure substance and a

mixture.

3a, 3b, 3c, 3d 41, 42, 48, 49

Perform calculations

involving percent as

applies to mixtures.

3-5, 3-6 3e, 3f, 3g 50, 52, 53, 55

3-4 Distinguish among the

forms and types of

energy.

4b, 4c 57, 59, 60

Define the terms

endothermic and

exothermic, providing

several examples of each

type of process.

4a 56

3-5 Perform calculations

involving the specific

heat of a substance, and

use them to identify a

substance.

3-7, 3-8, 3-9,

3-10

5a, 5b, 5c,

5d, 5e, 5f

63, 64, 67, 68,

69, 71, 79, 81

Questions for you – more familiar material

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• Choose the best answer describing the properties characteristic of a solid

a) lacks a definite shape

b) lacks a definite volume

c) has a definite shape and volume

d) has a definite volume

• The temperature at which a liquid changes into a gas is the

a) melting point

b) condensation point

c) boiling point

d) freezing point

• Choose the intensive (vs extensive) property: (extensive prop changes with amt, intensive does not)

a) color

b) mass

c) volume

d) conductivity

Chemical changes

a) Convert one substance into one or more other substances

b) Convert a liquid into a gas

c) Lower the density of a substance

d) Convert a solid directly to a gas

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Chemistry(Quick Review)

Chemistry - study of matter and the changes it undergoes

Matter - anything that has mass and occupies space

Law of the Conservation of Mass - matter is neither created nor destroyed in chemical reactions

Universe also contains energy

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Types of matter - Elements

The most basic form of matter under

ordinary circumstances

Simplest chemical substance

Only a few elements are found in their free

state (nitrogen, oxygen, gold, etc.)

Learn elements 1-36

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Compounds

A unique substance composed of two or more elements that are chemically combined (i.e. joined intimately, not just mixed together) also, molecular vs ionic

Compounds include substances like water, table salt, sugar

Pure compounds have definite compositions and properties (e.g. water, ethylene glycol)

Require complex chemical procedures to separate into simpler substances (elements)

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Properties of substancesProperties describe the particular characteristics of a substance

Pure substances have definite composition and definite, unchanging properties – the properties of mixtures can change

Physical properties - can be observed without changing the identity of a substance (BP, FP, gas, liquid, solid, etc)

Chemical properties - require that the substance change into another (A reacts with B to always from C, etc)

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Physical states

The three physical states are solid, liquid and

gas

solids - have a definite shape and volume

liquid - have a definite volume but not a definite

shape

gas - neither a definite volume or shape

A substance exists in a particular physical state

under defined conditions – temperature and

pressure (phase diagram H2O) (phase diagram CO2)

10

Phase changes (physical

properties)

Melting point or freezing point

temperature at which a substance changes

from solid to liquid

Boiling point or condensation point

temperature at which a substance changes

from liquid to gas (Normal bp and fp!)

Look again at water (phase diagram H2O)

11

Chemical properties

Chemical properties - involve how a

substance changes into another using a

reaction or heat

Sometimes quite difficult to determine

Some examples are burning (as opposed

to boiling) and color changes

Questions for you – less familiar

12

• Choose the substance with the greatest density (all densities in g/mL).

a) Ethyl alcohol – density = 0.79

b) Gold – density = 19.3

c) Table salt – density = 2.16

d) Lithium – density = 0.53

• What is the volume in mL of 77.8 g of table salt?

a) 98.5 mL

b) 4.03 mL

c) 36.0 mL

d) 147 mL

• Choose the heterogeneous mixture.

a) milk

b) Gatorade

c) sterling silver

d) tap water

• Choose the endothermic process.

a) photosynthesis of carbohydrates by plants

b) burning of gasoline in a car

c) rusting of iron

d) butter turning rancid

Choose the correct definition of a nutritional calorie.

a) amount of heat required to raise one gram of water one degree Celcius

b) 4.184 J

c) 10.0 cal

d) 1 kcal

13

Density (a physical property)

ratio of the mass of a substance to the volume of

that mass g/mL

Units usually g/mL for solids and liquids, (water

= 1.0 g/mL); g/L for gases

also a conversion factor relating the mass of a

substance to its volume

WORK PROBLEMS (13, 15, 20, 22)

Specific gravity is the ratio of the mass of a

substance to the mass of an equal volume of

water, e.g. 1.10 g/mL/1.0 g/mL = 1.1 S.G.

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Energy changes

Energy is the capacity to do work

Many forms of energy

heat

light

chemical (stored energy)

electrical energy

mechanical

nuclear

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Energy

Law of the Conservation of Energy -

energy cannot be created or destroyed,

but only transformed from one form to

another

The transformation from one type to

another may not be efficient (the efficiency

of transforming sunlight to electricity is

only about 35% efficient. The other 65%

is lost as heat.)

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Energy flowKinetic energy - energy resulting from motion

Potential energy is energy (potentially) available

due to position or composition

Exothermic reactions - produce energy

(release energy to the surroundings)

Endothermic reactions - require energy (store

energy)

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Temperature and specific heat

Recall that we measure temperature in °C or K

Energy units

calorie (cal) - amount of heat required to raise the

temperature of one gram of water from 14.5 °C to

15.5 °C (1 g 1 degree)

joule - 1 cal = 4.184 J (definition so exactly)

Nutritional calorie is actually 1000

(thermochemical) cal (indicated as 1 C but really

1 kcal in most fields other than nutrition)

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Specific Heat(A Physical Property of a Material)

Specific heat - the amount of heat required to raise the

temperature of one gram of a substance one degree

Celsius (or Kelvin)

Reflects how some substances heat up faster than

others

( C)

amount of heat energyspecific heat

mass t

amount of heat (cal or J) = Sp.ht X mass X DT

(Problems 63, 64, 69 - 70)

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Heat flow

When two substances at different

temperatures are in contact , or mixed,

heat flows from the substance at higher

temperature to the substance at lower

temperature

This heat flow continues until the temperatures

are the same

Temperature change depends on heat capacity

(Demo)

20

Specific Heat(A Physical Property of a Material)

Specific heat - the amount of heat required to raise the

temperature of one gram of a substance one degree

Celsius (or Kelvin)

Reflects how some substances heat up faster than

others

( C)

amount of heat energyspecific heat

mass t

(Problems) 63, 64, 69, 70

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Mixtures

Combinations of two or more substances

Can be separated by physical means

(filtration, distillation, crystallization,

chromatography)

Have chemical and physical properties

that are different from the pure substances

that make them up

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Types of MixturesHeterogeneous mixture - nonuniform mixture

containing two or more phases with definite

boundaries between the phases (e.g. ice and

water)

Phase - one physical state with distinct

boundaries and uniform properties

Homogeneous mixture - same throughout and

contains only one phase (substances are mixed

at the atomic or molecular level)

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Solutions

A type of homogeneous mixture, we will

use often

Usually involves a liquid phase, but can be

solid-solid, liquid-liquid, solid-liquid, etc.

The pure substances can be in different

phases but form a homogeneous mixture

(table salt and water, for example)

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Alloys

important solid solutions of two or more

metals (Alloys blend properties of the

components to give desired physical

property)

dental fillings (silver and mercury)

stainless steel (iron, chromium and nickel)

25

Percent by mass (or, volume)

Mass of specific material (unit)

Mass of specific material (unit)X 100% =

20 grams of NaCl is dissolved in 80 grams of water. What is

the concentration of the solution in percent by mass?

If I have a solution that is 43% by mass NaCl in water, how

many grams of NaCl are in 25 g of solution?