C1.4/5 - Boiling and More Changes of State

Question 1

After how many minutes does the substance below begin to boil?

Answer 1

5 minutes

Question 2

You are given 3 unknown substances.

Describe how you could use boiling points to identify the substances.

Answer 2

Heat each substance until it boils and record the boiling point.

Look up a list of different substance boiling points on the internet.

Compare the unknown substance boiling points with your list from the internet.

Question 3

What temperature does the substance below boil at?

Answer 3

100 ºC

Question 4

What do we call it when a gas turns into a liquid?

Answer 4

Condensation

Question 5

What is boiling?

Answer 5

When a substance is changing from a liquid to a gas state

Question 6

How do we make a substance boil?

Answer 6

We need to give enough thermal energy (heat) to its particles.

Question 7

If the temperature of a gas falls below its boiling point, what will happen?

Answer 7

It will condense back into a liquid

Question 8

What is evaporation?

Answer 8

When some particles in a liquid gain enough energy to escape from its surface. This is different to boiling!

Question 9

What is the difference between boiling and evaporation?

Answer 9

Evaporation happens at any temperature boiling happens only at the boiling point.

Evaporation is where particles escape from the surface of a liquid, boiling is where gas bubbles form throughout the liquid , rise and then escape,

Question 10

Use ideas about particles and evaporation to explain why sweating cools you down.

Answer 10

1. Sweat comes out of the pores in your skin.
2. Water from the sweat evaporates.
3. The water particles need energy to move away as a gas.
4. They take this energy from your skin, which cools you down.

Question 11

Describe what happens to particles of water when it boils.

Answer 11

1. Bubbles of steam form throughout the liquid.
2. In the bubbles particles are spread out.
3. In the liquid, water particles touch their neighbours.
4. As water boils, the steam bubbles rise to the surface of the liquid.
5. The steam bubbles escape into the air.
6. The steam particles mix with the air particles.

Question 12

A beaker of water is completely boiled into steam.

Is the number of water particles before and after boiling the same?

Answer 12

Yes - the number of particles are conserved (the same)

Question 13

The temperature that substances will boil at is called the…

Answer 13

boiling point