Unit 2: Matter and Change

OBJECTIVESStudents will be able to:1. define matter2. describe the states of matter (solid, liquid,

gas)3. identify the characteristics of of a substance,

element and compound4. distinguish between physical and chemical

change5. identify properties of matter (chemical,

physical, intensive, extensive)6. identify changes in matter that occur (physical

and chemical change)7. explain the law of conservation of mass

WHAT IS MATTER?• Matter is anything that takes up

space and has mass• Matter or not?

– gold– sound

– sunlight– air

– water– heat

– thoughts

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MASS & WEIGHT• Mass is the measure of the amount of

matter that makes up an object• Weight is a measure of the force of gravity on

an object– weight = mass x gravity– weight varies depending on distance from the

earth’s surface• Because the value never changes,

scientists use mass, not weight to measure matter

Shape Takes the shape of container

Takes the shape of container

Definite shape

Volume Fills volume of container Definite volume Definite

VolumeArrangeme

nt of particles

Random, far apart Random, close Fixed, close

Attraction between particles

Essentially none Strong Very strong

STATES OF MATTER

GAS vs. VAPOR• Gases and vapors are similar, but

terms should not be used interchangeably– Gas refers to a substance that is

naturally in the gaseous state at room temperature: hydrogen gas

– Vapor refers to the gaseous state of a substance that is a solid or a liquid at room temperature: water vapor

solid liquid gas

THE PHASES OF WATER

MatterAnything that has mass and takes up space

Pure SubstanceMatter with an

unique and unchanging composition

MixturesA combination of 2

or more pure substances

ElementPure

substance that cannot be broken into more simpler

substances

CompoundAtoms of two

or more elements that are

chemically united in a

fixed proportion

Homogeneous

Mixture/Solution

Mixture with a uniform

composition

Heterogeneous

MixtureMixture does not appear to be the same throughout

physical change

chemical

change

(PURE) SUBSTANCE • A substance is a form of matter with an

unique and unchanging composition (composition doesn’t change from sample to sample)

• Examples: Water, salt• What about salt water?• All pure substances are either elements or

compounds

ELEMENT• An element is a substance that cannot be

broken into more simpler substances• Examples: gold (Au), oxygen (O2)• To date, there are 118 elements

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COMPOUNDS• Compounds are substances composed of

atoms of two or more different elements that are chemically united in a fixed proportion– Water (H2O), sugar (sucrose, C12H22O11),

ammonia (NH3)• Compounds can be separated back into its

elements (by chemical means)– Electrolysis of water:

•2H2O 2H2 + O2

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PROPERTIES OF MATTER• Every pure substance has a unique set of

properties• A property is a characteristic that allows us

to recognize a certain type of matterPhysical properties of

waterclear liquid at room

temperatureboils at 100oCfreezes at 0oC

density at 4oC is 1.000 g/cm3

PHYSICAL PROPERTIES• Physical properties

are those properties that can be measured without changing the identity of the substance:– color, odor, melting point,

boiling point, density, hardness, taste

• Physical properties are either extensive or intensive

Extensive property

Intensive property

•A property that depends on the amount of a substance present•Example: Mass, volume, length•value will change when the amount of substance changes: 1 mL of water has a mass of 1 g while the mass of 1 L has a mass of 1000 g

•A property that is independent of the amount of substance present•Example: Density, boiling point, melting Point•value will not change when the amount of substance changes: The density of water is always 1.00 g/mL

CHEMICAL PROPERTIES• Chemical properties describe the way a substance may

change or react to form other substances– Corrosion, flammability

• The inability of a substance to change is also a chemical property– Argon gas is inert

• To observe a chemical property a chemical change must occur

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PROPERTIES OF COPPERPhysical properties Chemical properties

reddish brown, shiny

Forms a green copper carbonate compound when in contact with moist air

good conductor of heat

Forms new substances when combined with nitric & sulfuric acid

Density = 8.92 g/cm3 Forms deep blue

solution when in contact with ammonia

Melting point = 1085oCBoiling Point = 2570oC

CHANGES IN MATTER• A physical change is a change that

alters the appearance of the substance drastically but leaves its composition unchanged:– bend, grind, split, crush, boil, freeze,

melt, vaporize

Chemical Change (Chemical Reaction)

• In a chemical change a substance is transformed into a chemically different substance– When hydrogen burns in air it reacts with

oxygen to form water• The new substances formed have different

compositions and different properties• Terms: Explode, rust, oxidize, corrode,

tarnish, ferment, burn, rot etc.

EVIDENCE OF CHEMICAL CHANGEFormation of a gas or solid; color change;

energy change; odor

PHYSICAL OR CHEMICAL CHANGE?• Plants use carbon dioxide and

water to make sugar.• On a cold day, water vapor in the

air forms frost.

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THE LAW OF CONSERVATION OF MASS• Mass (matter) is neither created

nor destroyed during a reaction…mass is conserved:

Massreactants = Massproducts2HgO 2Hg + O216 g 200 g + 16

greactants products

PRACTICE PROBLEM1. In a complete reaction of 22.99 g

of sodium with 35.45 g of chlorine, what mass of sodium chloride is formed?

2. A 12.2-g sample of X reacts with a sample of Y to form 78.9 g of XY. What is the mass of Y that reacted?