Heating and Cooling

This worksheet describes the changes made to particles when materials are heated or cooled. Solid particles gain a considerable amount of energy and become conductors, whereas convection currents are created in liquids. Liquids would also evaporate into gases and there are various changes between the different states of matter.

Key stage:  KS 3

Curriculum topic:   Physics: Energy

Curriculum subtopic:   Energy Changes and Transfers

Difficulty level:

QUESTION 1 of 10

Protective clothing is needed by many people for various reasons. Every day, we wear clothing to protect us from the cold or the sun, but some people need safety clothing because they work under extreme conditions; for example, in high temperatures or in the cold sea.

The effectiveness of protective clothing depends on the material used and how its particles are affected by energy changes. Solid particles gain energy when heated, they vibrate more and pass the energy to each other as they bump into each other. This is called conduction, which means the energy flows through the solid materials. Hot solid particles need more space to vibrate, so solids expand, but when they cool down they contract.

Liquid particles are further away from each other than in solids, so conduction does not take place very well and gases can hardly conduct, as their particles are too far away from each other. Liquids and gases are fluids, so in fluids, heat energy travels better by convection. When a fluid is heated, the particles move around faster. The fluid also expands and becomes less dense, as the particles ‘spread around’, so there are less particles in the same space. The hotter part of the fluid starts to rise, whereas the cooler fluid around it takes its place.

Wind is an example of convection current. Some parts of the Earth are warmer than others and they heat the air above them. This then expands and rises and the cooler air from cooler parts takes its space. In turn, the cooler air is also heated, expands and rises. The process then repeats itself, forming winds.

This image shows the changes of state between solids, liquids and gases:

You can change substances from one state to another by heating or cooling. The freezing and melting point of a substance are always the same temperature. Changing from solid to liquid needs energy to break the bonds holding the particles together.

Heat energy can also be transferred as radiation, also referred to as infrared radiation. All hot things emit (give out) radiation. Dark, matte materials absorb (take in) more radiation than light and shiny ones, which reflect radiation more easily. Thermal imaging measures infrared radiation and converts it into temperature. Thermal imaging is used for filming at night, taking satellite images of the temperature of parts of the earth, designing outdoor clothing and weather forecasting.

Below is an example of a thermal image, showing the hotter parts of the building as red, orange and yellow and the cooler ones as blue and green.

What are the reasons people need various types of protective clothing? Tick two boxes.

To protect themselves from extreme working conditions.

To be trendy.

To warm up when it is cold.

To feel comfortable when exercising.

In the answer box below, write the word which completes this sentence:

In solids, heat is transferred by ____________.

In the answer box below, write the word which completes this sentence:

Solid particles ____________ when heated.

In the answer box below, write the word which completes this sentence:

When heated, solids ________, but when cooled they contract.

In the answer box below, write the word which completes this sentence:

Liquids and gases are _________.

In the answer box below, write the word which completes this sentence:

In fluids, heat travels better by ____________.

How are convection currents formed?

When part of a fluid is heated, it becomes less dense and rises. The cooler part then takes its place and in its turn, is heated and also rises. The process repeats itself.

When part of a fluid is heated, it becomes denser and rises. The cooler part then takes its place and in its turn, is heated and also rises. The process repeats itself.

When part of a fluid is heated, it becomes less dense and rises. The cooler part then takes its place and in its turn, is cooled and also rises. The process repeats itself.

When part of a fluid is cooled, it becomes less dense and rises. The cooler part then takes its place and in its turn, is heated and also rises. The process repeats itself.

Is the following statement true or false?

Winds are convection currents that happen due to the different amount of heat that reaches different parts of the earth from the sun.

true

false

What is the freezing and melting point of water? Write your answer in degrees Celsius, but just the number in the answer box.

Which type of energy is measured by thermal imaging?

From the list below, select the correct option to complete in this sentence:

‘Emit’ means to __________.

give out

absorb

reflect

take in

• Question 1

What are the reasons people need various types of protective clothing? Tick two boxes.

To protect themselves from extreme working conditions.
To warm up when it is cold.
EDDIE SAYS
People need protective clothing to protect themselves from extreme heat and cold. This helps isolate the body from outside temperatures
• Question 2

In the answer box below, write the word which completes this sentence:

In solids, heat is transferred by ____________.

conduction
EDDIE SAYS
This is the standard way heat is transferred in solids.
• Question 3

In the answer box below, write the word which completes this sentence:

Solid particles ____________ when heated.

vibrate
EDDIE SAYS
Particles in solids do not move around freely but only vibrate and when they are heated they gain more energy, so they vibrate more.
• Question 4

In the answer box below, write the word which completes this sentence:

When heated, solids ________, but when cooled they contract.

expand
EDDIE SAYS
Solid particles need more space as they vibrate more and faster, so they spread out and the solid expands.
• Question 5

In the answer box below, write the word which completes this sentence:

Liquids and gases are _________.

fluids
EDDIE SAYS
Fluids have particles which are far away from each other. Particles in solids are compacted and close together, and do not move around.
• Question 6

In the answer box below, write the word which completes this sentence:

In fluids, heat travels better by ____________.

convection
EDDIE SAYS
Convection is when heat transfers through the movement of fluids.
• Question 7

How are convection currents formed?

When part of a fluid is heated, it becomes less dense and rises. The cooler part then takes its place and in its turn, is heated and also rises. The process repeats itself.
EDDIE SAYS
Hot air or water becomes less dense and feels lighter, so it rises up, pushing the rest downwards, as it takes its place.
• Question 8

Is the following statement true or false?

Winds are convection currents that happen due to the different amount of heat that reaches different parts of the earth from the sun.

true
EDDIE SAYS
It is the same principle as a convection current in your house; but, because it is in a bigger scale, strong winds can be formed.
• Question 9

What is the freezing and melting point of water? Write your answer in degrees Celsius, but just the number in the answer box.

0
EDDIE SAYS
Water becomes ice at 0°C (degrees Celsius), but also starts melting at the same temperature.
• Question 10

Which type of energy is measured by thermal imaging?

EDDIE SAYS
Thermal imaging measures infrared radiation and converts int into temperature.
Heat can be transferred by conduction, convection and radiation, depending on the medium available; i.e. solid, fluid or vacuum (no particles at all).
• Question 11

From the list below, select the correct option to complete in this sentence:

‘Emit’ means to __________.

give out
EDDIE SAYS
Emit is the scientific word for heat being given out of any material.
---- OR ----

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