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GCSE Physics

Solids, liquids and gases

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Lesson 4 – The structure of matter

Aims:

•To understand that a substance can change state from solid to liquid by the process of melting

•To understand that a substance can change state from liquid to gas by the process of evaporation or boiling

•To recall that particles in a liquid have a random motion within a close-packed structure

•To recall that particles in a solid vibrate about fixed positions within a close-packed regular structure

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What are the three states of matter?

solid liquid gas

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Solids

Definite shape,

Definite volume,

Particles close together, fixed,

Particles move relatively slowly.

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Liquids

No definite shape, definite volume,

Take the shape of container,

Particles are close together, but mobile

Particles move a little quicker.

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Mercury

•Mercury is the only metallic element that is a liquid at room temperature.

•It is more than 13 times heavier than water.

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Gases

No definite shape

No definite volume

Take the shape and volume of container

Particles are far apart

Particles move fast

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Comparing states

Definite

volume

Definite

Shape

Compressible Temperature increase

Solid

Liquid

Gas

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Comparing states

Definite

volume

Definite

Shape

Compressible Temperature increase

Solid Yes

Liquid Yes

Gas No

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Comparing states

Definite

volume

Definite

Shape

Compressible Temperature increase

Solid Yes Yes

Liquid Yes No

Gas No No

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Comparing states

Definite

volume

Definite

Shape

Compressible Temperature increase

Solid Yes Yes No

Liquid Yes No No

Gas No No Yes

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Comparing states

Definite

volume

Definite

Shape

Compressible Temperature increase

Solid Yes Yes No Small

Expansion

Liquid Yes No No Small

Expansion

Gas No No Yes Large

expansion

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solid particles…- are very close together in a fixed arrangement - have a small amount of energy- vibrate but do not move  

liquid particles…- are close together but have no fixed arrangement - have more energy than solid particles- vibrate and can move about 

gas particles…- are far apart and have no fixed arrangement- have a large amount of energy- move rapidly in all directions 

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Changing state

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Changing states of matter

Solids can turn into liquids, and liquids can turn into gasses and back again - depending on the temperature.

So, we can use the effect of heat on states of matter to measure the temperature of something.

COLD WARM HOT

Solid Liquid Gas

Melt Boil

CondenseFreeze

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Changing state is a physical

change.

Liquid

Sublimation

Melting Vaporization

Condensation

Condensation

Solid

Freezing

Gas

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Sublimation

• Sublimation is the physical changing of a solid into a gas.

• Only a very few substances change from a solid to a gas without becoming a liquid.

• Carbon dioxide is an example of a compound that sublimes.

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Changing state graphs

Water

Waterand IceIce

Water and Steam

Steam

-20

0

20

40

60

80

100

120

0 40 120 220 760 800

Heating Curve for Water

Time in seconds

Tem

pera

ture

(de

gree

s C

elsi

us)

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Energy is transferred when

something changes state.

Water

Waterand IceIce

Water and Steam

Steam

-20

0

20

40

60

80

100

120

0 40 120 220 760 800

Heating Curve for Water

Time in seconds

Tem

pera

ture

(de

gree

s C

elsi

us)

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Liquid to a gas

•At its boiling point water changes state from a liquid into a gas.

•Energy must be transferred to the water so that it’s molecules can change from a liquid to a gas.

Water

Waterand IceIce

Water and Steam

Steam

-20

0

20

40

60

80

100

120

0 40 120 220 760 800

Heating Curve for Water

Time in seconds

Tem

pera

ture

(de

gree

s C

elsi

us)

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Ice to water

•When an ice cube at zero Celsius is left on a table on a warm day it will melt.

•Energy from the room is transferred to the ice cube to change it from a solid to a liquid.

•When all of the ice has melted the water will start to increase in temperature towards that of the room.

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Water to ice•Place water into an ice cube tray and then place it into a freezer.

•The water in the tray is hotter than the freezer. As energy is transferred from the water to the freezer the temperature drops.

•At zero degrees Celsius the water keeps transferring energy to the freezer but does not get colder. Instead the water changes state from a liquid to a solid.

•When all of the water has turned to ice it will again start to fall in temperature until it has the same temperature as the freezer compartment.

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Two states at the same temperature

Water

Waterand IceIce

Water and Steam

Steam

-20

0

20

40

60

80

100

120

0 40 120 220 760 800

Heating Curve for Water

Both Water and

Steam

Time in seconds

Tem

pera

ture

(de

gree

s C

elsi

us)

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At 100 degrees Celsius water and

steam can both occur

Water

Waterand IceIce

Water and Steam

Steam

-20

0

20

40

60

80

100

120

0 40 120 220 760 800

Heating Curve for Water

Ice and

Water

Time in seconds

Tem

pera

ture

(de

gree

s C

elsi

us)

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At zero degrees Celsius both ice

and water can both occur.

Water

Waterand IceIce

Water and Steam

Steam

-20

0

20

40

60

80

100

120

0 40 120 220 760 800

Heating Curve for Water

Time in seconds

Tem

pera

ture

(de

gree

s C

elsi

us)

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Summary – The structure of matter

•A substance can change state from solid to liquid by the process of melting

•A substance can change state from liquid to gas by the process of evaporation or boiling

•Particles in a liquid have a random motion within a close-packed structure

•Particles in a solid vibrate about fixed positions within a close-packed regular structure

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• The three states of matter are . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . and . . . . . . . . . . . . . . . . . . . All matter consists of tiny . . . . . . . . . . . . . . . . . . travelling at . . . . . . . . . . . . . speed.

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• A solid has a definite size and a definite . . . . . . . . . . . . . . . . . . because the forces between its . . . . . . . . . . . . . . . . . . are very . . . . . . . . . . . . . . . . . . . A liquid has weaker forces between its . . . . . . . . . . . . . . . . . . and so does not have a definite . . . . . . . . . . . . . . . . . . .

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• If a substance is cooled down, its molecules move at a . . . . . . . . . . . . . . . . . . speed. When some molecules pass through some other molecules, we call it . . . . . . . . . . . . .    The twisting and jerking of smoke particles when they are hit by air . . . . . . . . . . . . . . . . . . is called . . . . . . . . . . . . . . . . . . .

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Evaporation and Boiling

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Evaporation

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Evaporation

• Liquid cools because it loses higher energy molecules or atoms

• Air cools because the molecules leaving give up a lot of energy to break free, so they have much lower energy after they gain their freedom

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• Evaporation from liquids takes place at all temperatures;

• it occurs when particles at the surface gain enough energy to move away from the attractive forces of neighbouring particles..

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How to make a liquid evaporate more quickly?

• Increase the temperature

• Increase the surface area

• Reduce the humidity

• Blow air across the surface

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Boiling

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Boiling

• Molecules break free of the liquid bonds and form little bubbles

• If the vapor pressure in the bubble is large enough to resist the pressure of the liquid, and the air pressure above the interface they rise and escape to the outside

• Remember, liquid is cooling and air is cooling

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Boiling in a liquid only takes place at the boiling point;

when a liquid boils, bubbles of vapour form in the body of liquid and rise to the surface, where they collapse and release the vapour into the atmosphere

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Changing the boiling point

• Impurities

Impurities raise the boiling point of water.

• Pressure

Reduce the pressure lowers the boiling point.

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Pressure cooker

P≈2P0,

boiling point at about 120℃

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rapid ,gas bubbles are produced throughout.

slow; occurs at the surface.

When will these phenomenon occur?

What will happen during and after these phenomenon?