3. Heating Processes

Question 1

What is the difference between solids, liquids and gases?

Answer 1

They have different amounts of energy

Question 2

What is Specific heat capacity?

Answer 2

It is the amount of energy required to change the temperature of one kilogram of a substance by 1’C

Question 3

E = m × c × θ

Answer 3

Energy transferred (Joules) = Mass (kg) x specific heat capacity x change in temperature

Question 4

What is Specific Latent Heat of Vaporisation?

Answer 4

The amount of energy required to change the state of one kilogram of a substance from a liquid to a gas with no change of temperature

Question 5

E = m x Lv

Answer 5

Energy (Joules) = Mass (kg) x Specific latent heat of Vaporisation

Question 6

What is Specific Latent Heat of Fusion?

Answer 6

The amount of energy required to change the state of one kilogram of a substance from a solid to a liquid with no change in temperature

Question 7

E = m x Lf

Answer 7

Energy (J) = Mass (kg) x Specific Latent Heat of Fusion

Question 8

What is the link between temperature and infrared radiation emitted?

Answer 8

The hotter an object is the more infrared radiation it radiates in a given time

Question 9

Dark, matte surfaces:

Answer 9

Good absorbers and good emitters of infrared radiation

Question 10

Light, shiny surfaces:

Answer 10

Poor absorbers and poor emitters of infrared radiation

Good reflectors of infrared

Question 11

What do U-values measure?

Answer 11

How good an insulator something is

The lower the U-value the better the insulator

Question 12

How do solar panels work?

Answer 12

Solar panels may contain water, this water is heated by radiation from the sun, then it is used to heat buildings or provide domestic hot water

Question 13

Energy:

Answer 13

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed

Question 14

What happens to wasted energy?

Answer 14

It is eventually transferred to surroundings, which become warmer
This energy becomes increasingly spread out and so becomes less useful

Question 15

How can you represent energy flow in a system?

Answer 15

A Sankey diagram

Question 16

Sankey diagrams:

Answer 16

Should be draw to scale

So the width of the ‘energy in’ arrow should equal the combination of all the ‘energy out’ arrows

Question 17

How can heat energy be transferred?

Answer 17

Through convection and conduction

Through evaporation and condensation

Question 18

Convection:

Answer 18

Liquids and gases expand when they are heated
The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way, convection currents that transfer heat from place to place are set up.

Question 19

Conduction:

Answer 19

Electrons free to carry charge move through lattices carrying electrical charge and heat energy

Question 20

the rate at which an object transfers energy is determined by?

Answer 20

Its surface area and volume
The material it is made from
The nature of the surface with which the object is in contact with

Question 21

The greater the temperature gradient…

Answer 21

The greater the rate of energy transfer

Question 22

efficiency = useful power out / total power in

Answer 22

or

efficiency = useful energy out / total energy in