Unit 1: 1 - Energy Transfer by Heating

Question 1

What is the human organ that detects infrared radiation?

Answer 1

The skin.

Question 2

What type of radiation do all objects emit?

Answer 2

Infrared radiation.

Question 3

What emission is proportional to the temperature of an object?

Answer 3

Infrared (the hotter the object, the more infrared radiation is given off).

Question 4

How can infrared radiation reach the Earth and keep it warm?

Answer 4

As it is part of the light (electromagnetic) spectrum, it can travel through a vacuum.

Question 5

What types of surfaces are good absorbers of infrared radiation?

Answer 5

Dark, matt surfaces.

Question 6

What type of surfaces are good emitters of infrared radiation?

Answer 6

Dark, matt surfaces.

Question 7

What type of surfaces are good reflectors of infrared radiation?

Answer 7

Light, shiny surfaces.

Question 8

What are the 3 (main) states of matter?

Answer 8

Solid, liquid and gas.

Question 9

What state of matter does conduction mainly occur?

Answer 9

Solids (liquids and gases are poor conductors).

Question 10

What are the best conductors and why?

Answer 10

Metals, as they contain free electrons that can carry energy. These gain energy and collide more into other particles and transfer.

Question 11

How does a solid conduct heat?

Answer 11

The particles are heated at one end, so they gain kinetic energy and vibrate more. The particles then vibrate into each other and transfer this energy to adjacent particles - which transfers heat along the solid.

Question 12

Poor conductors are called…

Answer 12

Insulators.

Question 13

What materials does convection mainly occur in?

Answer 13

Fluids (liquids and gases).

Question 14

How does convection conduct energy through materials?

Answer 14

When a fluid is heated it expands. The fluid then becomes less dense and rises. The warm fluid is replaced by a cooler, denser fluid. The resulting convection current transfers energy throughout the fluid.

Question 15

Why doesn’t convection occur in solids?

Answer 15

Because the particles in solids are fixed in place so they cannot move around.

Question 16

What is evaporation?

Answer 16

When a liquid turns into a gas.

Question 17

Give 3 ways to increase the rate of evaporation.

Answer 17

• Increasing the surface area of a liquid;
• Increasing the temperature of a liquid;
• Creating a draught of air across the liquid’s surface.

Question 18

What is condensation?

Answer 18

When a gas turns into a liquid.

Question 19

Give 2 ways to increase the rate of condensation.

Answer 19

• Increasing the surface area;
• Reducing the surface temperature.

Question 20

The greater the temperature difference between an object and its surroundings, ____.

Answer 20

The greater the rate in which energy is transferred.

Question 21

Apart from the temperature differences, give 3 factors that affect the rate at which energy is transferred.

Answer 21

• The object’s surface area;
• The object’s shape;
• The materials the object is in contact with.

Question 22

Give 3 ways in which to maximise the energy transfer.

Answer 22

• Use good conductors;
• Colour an object dull black;
• Have the air flow around the object maximised.

Question 23

Give 3 ways in which to minimise energy transfer.

Answer 23

• Prevent convection currents (and conduction) by trapping air in small pockets in a solid;
• Use materials that are good insulators;
• Colour materials white and shiny.

Question 24

How does a vacuum minimise heat transfer?

Answer 24

Because it contains no particles, so conduction and convection currents cannot occur.

Question 25

What is the specific heat capacity of an object?

Answer 25

The amount of energy required to raise the temperature of 1kg of a substance by 1°C.

Question 26

The greater the mass of an object, the more … to heat it.

Answer 26

Energy is required

Question 27

What is the unit of specific heat capacity?

Answer 27

J/kg°C.

Question 28

How do we work out energy transfer using SHC (given on the formula sheet)?

Answer 28

E=m * c * Θ

Energy transferred (J) = Mass (kg) * specific heat capacity (J/kg°C)* temperature change (°C)

Question 29

Give at least 4 ways to insulate a building (with reasons).

Answer 29

Any 4 from…

• Fibreglass loft insulation (to reduce energy by conduction);
• Cavity wall insulation (traps air in pockets to reduce energy transfer by convection);
• Double/Triple glazing (to reduce energy transfer by conduction through windows);
• Draught proofing (to reduce energy transfer by convection);
• Aluminium foil behind radiators (to reflect infrared radiation back into a room).

Question 30

What is the U-value of an object?

Answer 30

The U-value of a material tells us how much energy per second passes through it (the lower the U-value the better the insulator).

Question 31

What do solar heating panels do?

Answer 31

Capture the Sun’s energy to heat water.

Question 32

Give 2 advantages and 2 disadvantages of solar heating panels.

Answer 32

Advantages:

• Cheap to run (as they don’t use fuel);
• Release no greenhouse gases while they are running.

Disadvantages:

• Expensive to buy and install;
• The water is not heated at night or in bad weather.