Heat

Question 1

Heat

Answer 1

Is the form of energy transferred from the hotter substance to the cooler substance as a result of the temperature difference between them.

Question 2

Temperature

Answer 2

A measure of coldness or hotness of a body

Question 3

Internal Energy

Answer 3

The energy possessed by a body due to the random vibrations of its’ molecules.

Question 4

Thermometric property

Answer 4

Any physical property that changes measurably with temperature

Question 5

Heat Capacity

Answer 5

The amount of heat energy required to change an object’s temperature by 1K

Question 6

Specific Heat Capacity

Answer 6

The heat energy required to change the temperature by 1K for a substance of 1kg

Question 7

Latent Heat

Answer 7

The heat energy required to change an object’s state without a change in temperature.

Question 8

Specific Latent Heat

Answer 8

Amount of heat energy needed to change the state of a 1kg substance without a change in temperature.

Question 9

Specific latent heat of fusion

Answer 9

Amount of heat energy needed to change 1kg of a substance from a solid to a liquid without a change in temperature

Question 10

Specific latent heat of vapourisation

Answer 10

Amount of heat energy needed to change 1kg of a substance from a liquid to a gas without a change in temperature

Question 11

Convection

Answer 11

The circulation of heat in a fluid due to the motion of the fluid itself.

Question 12

Conduction

Answer 12

The transfer of heat with no net movement of the medium due to a difference in temperature within the medium.

Question 13

Radiation

Answer 13

The transfer of heat between two points by means of electromagnetic waves

Question 14

Solar Constant

Answer 14

Average amount of the Sun’s energy falling per second perpendicularly on 1m squared on the Earth’s atmosphere.

Question 15

U-value

Answer 15

A measure of the heat flow through 1 m2 of material each second when a temperature difference of one kelvin exists between the two sides

Question 16

Why is a standard thermometer necessary?

Answer 16

Different thermometers based on different thermometric properties give slightly different values for the same temperature.

Question 17

How many kelvin in 0 degrees celsius?

Answer 17

273.15 K

Question 18

Give four examples of thermometric properties.

Answer 18

Volume of column of mercury
Emf of a thermocouple
Resistance of Wire
Colour of liquid crystals

Question 19

Name one essential feature of a clinical thermometer.

Answer 19

Constriction

Question 20

In words explain the operation of a heat pump?

Answer 20

1. Volatile liquid called refrigerant with low boiling point flows along a pipe as shown.
2. This liquid takes heat energy from the air and food inside the fridge and the liquid is vaporised to a gas.
3. The air and food inside the fridge is now cooler
4. The gas flows into condenser unit and is compressed back to a liquid releasing latent heat to the surrounding air.
5. The cycle repeats until a certain low temperature inside the fridge is achieved which is determined by a thermostat control.

Question 21

What is the function of operation of a heat pump?

Answer 21

A heat pump takes energy from a cooler region and transfers it to a warmer region.

Question 22

How does perspiration occur?

Answer 22

1. When we exercise are body temperature rises.
2. Liquid forms on skin and is vapourised.
3. Latent heat needed to vapourise so heat is taken from the body which is lowered to normal temperature.

Question 23

Why does the high specific latent heat of ice make it a good coolant?

Answer 23

Takes in a lot of heat energy when melting.

Question 24

How can an object be engineered to reduce heat loss? (3)

Answer 24

Add insulating lid
Lag with cotton wool
Reduce specific heat capacity of materials

Question 25

Is water a good or bad material for a thermocouple? Why?

Answer 25

Bad material.
Poor conductor of heat

Question 26

Explain why heat doesn’t travel through a solid due to convection.

Answer 26

The particles cannot move freely.

Question 27

Explain the principle of a storage heater.

Answer 27

Large specific heat capacity.

Heated at night when electricity is cheaper and store a large quantity of energy with this energy released slowly during the day.

Question 28

How can energy be supplied at a constant rate?

Answer 28

Heating coil + joulemeter

Question 29

How does the colour black relate to heat?

Answer 29

Good adsorber of heat energy.

Question 30

Name the three ways in which heat loss can occur?

Answer 30

Conduction
Convection
Radiation

Question 31

Give one advantage of a geothermal heating system over a solar heating system.

Answer 31

Geothermal system functions all the time. Solar heating system works only during the daytime.

Question 32

Give an advantage of using kelvin as S.I. unit of temperature.

Answer 32

Gas laws measured in Kelvin.
Always Positive

Question 33

Give an advantage of a thermocouple thermometer over a mercury thermometer. (2)

Answer 33

less fragile
mercury is toxic