Heat

Question 1

What is heat

Answer 1

A form of energy

Question 2

What is temperature

Answer 2

The measure of how hot or cold an object is

Question 3

SI unit of heat energy and Temperature

Answer 3

Heat: Joules (J)
Temperature: Kelvin (K)

Question 4

What is the movement of heat

Answer 4

From a hotter region to a colder region

Question 5

What is conduction

Answer 5

The transfer of heat without the physical movement of the medium

Question 6

What is the order of conduction and why

Answer 6

1. Solid — Liquid — Gas
2. As the particles are closer packed in solids than gasses, the heat passes to each particle easier

Question 7

What are the characterisitics of Expansion

Answer 7

1. The temperature increases
2. The object gains heat
3. The particles move faster and further apart

Question 8

What are the characterisics of Contraction

Answer 8

1. The temperature decreases
2. The object loses heat
3. The particles move slower and closer together

Question 9

Case of Expansion in solids

Answer 9

1. In hit weather, a metal railway gains heat and expands
2. If the track was made in 1 continuous strip it would buckle
3. This can cause the train to derail
4. Hence, expansion gaps are made for the track to safely expand

Question 10

Case of Contraction in solids

Answer 10

1. In cold weather, the power lines and network cables loose heat and contract
2. if the lines are exactly straight, they might snap if the cable gets too tight
3. Hence they are made loose to let it safely contract

Question 11

What is a bimetalic strip

Answer 11

A strip of metal made of two different metals that expand at different rates
(brass on top steel below)

Question 12

Which expands/contracts more in the bimetalic strip

Answer 12

Brass

Question 13

What is the concept of a hot air balloon

Answer 13

Hot air rises and cold air sinks
(The flame heats the air allowing it to rise)

Question 14

Why are metals better conductors of heat

Answer 14

The particles are much more closely packed and this allows the transfer of heat energy to occur quicker

Question 15

What is Convection

Answer 15

The transfer of heat from one place to another by the movement of the medium

Question 16

Describe the process of convection in a liquid

Answer 16

1. The water at the bottom of the flask is heated up and it gains heat
2. As the volume of water at the bottom increases, it decreases in density
3. The change of density allows it to rise to the top of the flask
4. Due to having a lower density, the water at the top sinks to the bottom
5. This continues and convection currents are formed in the water allowing heat energy to be distributed evenly throughout the water.

Question 17

Explain the convection process in gasses

Answer 17

1. The air above the candle gains heat and expands
2. The decrease in density allows it to rise up.
3. The cooler air in the other chimney moves down to take the place of the risen air.
4. This then forms a convection current

Question 18

What is radiation

Answer 18

The transfer of heat without the need of a medium

Question 19

What are the factors that affect conduction

Answer 19

1. Particulate State of medium
2. Material of solid

Question 20

Factors that affect radiation

Answer 20

Temperature, Surface area, Color and texture of the surface

Question 21

How does Temperature affect radiation

Answer 21

The hotter the object, the higher rate of radiation from it

Question 22

How does Surface area affect radiation

Answer 22

The larger the surface area, the higher the rate of radiation

Question 23

How does Texture of a surface affect radiation

Answer 23

The rougher the surface, the higher the rate of radiation

Question 24

how does colour of a surface affect radiation

Answer 24

The duller the colour of the surface, the higher the rate of radiation