STATES OF MATTER

EXPANSION and CONTRACTION

of LIQUIDS and GASES

Learning Points• State that matter expands when it

is heated and contracts when cooled.

• Explain the expansion and contraction of solids, liquids and gases in terms of particle theory.

• Describe applications of expansion of solids, liquids and gases.

Mercury and alcohol are liquids that expand and contract in thermometers.

Expansion & contraction of liquids

EXPERIMENT

AIM: To find out what happens to liquids when they are heated and cooled.

INSTRUCTIONS

1. Fill two test-tubes to near the top with the red coloured water provided.

1. Place the tops on the test-tubes and secure them using a clamp-stand.

3. Lower the test-tubes into a beaker containing either hot or cold water.

4. Watch what happens to the level of the red water in each test-tube over the next 5 minutes.

WHAT DID YOU FIND OUT?

Q. Can you explain why liquids expand when they are heated and contract when they are cooled?

Q. What happens to how the particles in the red liquid are arranged when they are heated and then cooled?

SOME QUESTIONS?

EXPLANATION

• The particles in liquids are a little further apart to each other than is the case in a solid.

• When a liquid is heated the distance between its particles become larger and it expands.

• When the liquid is cooled it contracts and its the particles move back close to each other.

Air expands when heated (becoming less dense) so it floatsThis is how hot air balloons work.

Expansion & contraction of gases

EXPERIMENT

AIM: To find out what happens to gases when they are heated and cooled.

INSTRUCTIONS1. Draw out the following table.

TEST-TUBE NUMBER OF AIR BUBBLES

LEAVING FOR 5 MINUTES BEFORE

HEATING

DURING HEATING FOR5 MINUTES

LEAVING FOR 5 MINUTES AFTER

HEATING

INSTRUCTIONS2. Collect a test-tube with a glass tube sticking out of it.

3. Place the test-tube upside down with the glass tube sticking into the water and secure them using a clamp-stand.

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INSTRUCTIONS4. Count the number of bubbles of air coming out of the bottom of the glass tube for 5 minutes.

5. Write down the number of bubbles produced in the table.

INSTRUCTIONS6. Carefully warm up the test-tube with your hands for 5 minutes.

7. Write down the number of bubbles produced in the table.

INSTRUCTIONS8. Take your hands away and allow the test-tube to cool for 5 minutes.

9. Write down the number of bubbles produced in the table during this cooling down period.

WHAT DID YOU FIND OUT?

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WHAT DID YOU FIND OUT?• The heat from the hands made the air in the

test tube heat up and expand. The expanded

air pushed out of the test-tube and into the water as bubbles.

• When the hot hands were taken away, the air

in the test tube became cooler and the air began to cool.

• The space in the test-tube taken up by the air

that escaped during heating was replaced by

water moving into the test-tube.

EXPLANATION• The particles in gases are further

apart to each other than is the case in a solid or liquid and are easier to expand.

• When a gas is heated the distance between its particles become larger and it expands.

• When the gas is cooled it contracts and its the particles move back to their starting positions.