Topic 1

The particulate nature of matter

1.1- The states of matterMatter substance that has mass and occupies space.

Matter can exist as a solid, a liquid or a gas.

These three forms of matter are called the states of matter.

Property Solid Liquid Gas

Shape fixed not fixed not fixed

Volume fixed fixed not fixed

Compressibility can’t be compressed

can’t be compressed

can be compressed

1.2- Kinetic particle theoryThe kinetic particle theory states that:

“all matter is made up of tiny particles and that these particles are in constant random motion”

The kinetic particle theory is used to:◦describe the states of matter◦explains the differences in the properties of solid, liquids,

gases◦explains the changes in state of matter.

Characteristic Solid Liquid Gas

Arrangement of particles

► orderly► closely packed

► disorderly► less closely packed

► disorderly► very far apart

Attractive forces between particles

very strong strong very weak

Kinetic energy of particles

very low low high

Motion of particles

vibrate and rotate about fixed position

move freely throughout the

liquid

move rapidly in any direction

1.3- Changes of stateMatter can change from one state to another.

When matter is heated or cooled, the heat energy taken in or given out causes the kinetic energy of the particles to change. As a result, there is a change in state.

Melting -1-Changes of state from a solid to a liquid.

The temperature at which a solid becomes a liquid is called its melting point.

Different substances have different melting points.

Substance oxygen ethanol ice iron

Melting point/0C

-219 -114 0 1535

Melting -2-

What happens to the particles of a solid that is heated until it melts?

1. Heat energy is absorbed by particles of a solid.2. Heat energy is converted into kinetic energy.3. The particles vibrates, until the vibrations of the particles

overcome the forces of attraction between them.4. The particles begin to break away from their fixed positions.5. Finally, all of the particles aren’t in their fixed positions.6. The substance is now a liquid.

Melting -3-

A

B C

D

A-BThe temperature of solid increases until it reaches its melting point. B solid starts to melt.

B-CDuring melting process, temperature

of substance remains constant even though heating continues.

A mixture of solid and liquid exists here.

C-D All solids has melted and

temperature of liquid rises as heating continues.

Temperature/0C

Time/min

Freezing -1-Changes of state from a liquid to a solid.

The temperature at which a liquid becomes a solid is called its freezing point.

A pure substance melts and freezes at the same temperature.

Freezing -2-

What happens to the particles of a liquid that is cooled until it freezes?

1. Heat energy is given out by particles of a liquid.2. The particles lose kinetic energy and begin to move more slowly.3. The particles are no longer have enough energy to move freely.4. The particles start to settle into fixed positions.5. Finally, all of the particles settled into fixed positions.6. The substance is now a solid.

Freezing -3-

P

Q R

S

Temperature/0C

Time/min

P-QThe temperature of liquid decreases until it reaches its freezing point. Q liquid starts to freeze.

Q-RDuring the process, temperature of

substance remains constant even though cooling continues.

A mixture of solid and liquid exists here.

R-SAll liquids has frozen and

temperature of solid drops as cooling continues.

BoilingChanges of state from a liquid to a gas.

The temperature at which a liquid boils is called its boiling point.

Different substances have different boiling points.

W

X Y

ZTemperature/0C

Time/min

W-X Liquid heats upX-Y Liquid BoilsY-Z Gas heats up

Evaporation -1-Changes of state from a liquid to a gas at temperatures lower

than its boiling point.

Evaporation occurs because some particles have enough energy to escape as a gas from the surface of the liquid.

Liquids that evaporate quickly at room temperature are called volatile liquids.

They usually have boiling points just above room temperature.

Examples: perfume and petrol

Evaporation -2-

Boiling Evaporation

occurs only at boiling point occurs at room temperatures below boiling point

occurs throughout the liquid occurs only at the surface of the liquid

occurs rapidly occurs slowly

Condensation Sublimation

Changes of state from a gas to a liquid.

Changes of state from a solid to a gas.

Occurs because particles at the surface of the solid have enough energy to break away from the solid and escape as a gas.

Ex: iodine, dry ice

How to determine the state of a substance?

m.p. b.p.

SOLID LIQUID GAS

The table below gives information about six substances, A, B, C, D, E and F.

Substance A B C D E FM.P./0C -188 -114 17 36 300 808B.P./0C -42 37 118 344 580 1465

A. Classify the substance A to F as solids, liquids or gases at room temperature (0C).

B. Which substance will change from a liquid to a solid when placed in a refrigerator (4 0C)?

C. (i) Which substance will change to a liquid only at 37 0C?(ii) Which substance will undergo change in state only at 37 0C?

D.Which substance is a volatile liquid?

The AnswersA. Solid D, E and F

Liquid B and C Gas A

B. C

C. (i) D(ii) B

D. B

1.4-Diffusion

DiffusionDiffusion is the movement of particles from a region of higher

concentration to a region of lower concentration.

Diffussion does not occur in solids.

Diffusion in liquids is much slower than in gases (because the particles move slower in the liquid phase than in the gas phase).

The rate of diffusion is affected by relative molecular mass and temperature.

Ar /Mr Rate of diffusion

Temperature Rate of diffusion