P1.1 Energy Transfer by Heating

Question 1

How does sublimation happen?

Answer 1

Sublimation is the change of state between a solid and a gas, an example of this is dry ice. This happens because it gains thermal energy which transfers into kinetic energy turning it into a gas.

Question 2

What objects emit heat radiation?

Answer 2

Anything above 0 degrees K

Question 3

Describe the arrangement of particles in a solid.

Answer 3

Close together in a regular pattern.

Question 4

Describe the arrangement of particles in a liquid.

Answer 4

Close together and random.

Question 5

Describe the arrangement of particles in a gas.

Answer 5

Far apart and random.

Question 6

Describe the movement of particles in a solid.

Answer 6

Vibrate about a fixed position.

Question 7

Describe the movement of particles in a liquid.

Answer 7

Move around each other.

Question 8

Describe the movement of particles in a gas.

Answer 8

Move around quickly in any direction.

Question 9

State four different transfers of energy.

Answer 9

Conduction, convection, evaporation and condensation.

Question 10

Give two examples of convection.

Answer 10

Immersion heater.

Radiator.

Question 11

Give an example of evaporation.

Answer 11

Sweating

Question 12

Give an example of conduction.

Answer 12

A saucepan on a hob.

Question 13

What two things are dark, matt surfaces good at?

Answer 13

Absorbing infrared radiation.

Emitting infrared radiation.

Question 14

State the three things at which the rate of an object transferring energy by heating depends on.

Answer 14

Surface area and volume.
The material from which the object is made.
The nature of the surface it is contacting.

Question 15

How do you calculate specific heat capacity?

Answer 15

m x c x feta

Question 16

Why are steel electric kettles often made very shiny?

Answer 16

because shiny surfaces are poor emitters therefore they lose less heat by radiation.

Question 17

The hotter a surface is the more…?

Answer 17

radiation it radiates

Question 18

what happens in terms of particles when a solid melts into a liquid?

Answer 18

particles will gain more kinetic energy. They will vibrate more and move faster to eventually overcome the strong forces of attraction that hold the particles in a solid together.

Question 19

how do the change in particles energy cause a convection current in a room?

Answer 19

The particles have more energy so the distance between them becomes greater therefore the air expands and becomes less dense. This reduction in density means the hot air rises above the cooler denser air.

Question 20

what factor would increase the rate of the evaporation of a liquid?

Answer 20

The liquid has a high temperature low density large surface area or low concentration

Question 21

factors that increase the rate of condensation of gas?

Answer 21

The temperature of the surface the gas touches is lower or if the surface area of the surface the gas touches is larger.

Question 22

what for features of a vacuum flask reduces heat transfers?

Answer 22

shiny surface - reduce radiation
plastic stopper - reduces conduction
Vacuum gap between walls of bottle - reduce convection

Question 23

why do the hairs on your skin stand up when you are cold?

Answer 23

to trap insulating air around your body to limit the amount of heat lost by convection.

Question 24

why do some people skin go pink when they are hot?

Answer 24

The body diverts more blood to flow near the surface of the skin so that more heat can be lost by radiation.

Question 25

why would an arctic animals have small ears?

Answer 25

to minimise heat loss by radiation and stay warm.

Question 26

how could we insulate our house?

Answer 26

loft installation, double glazing, cavity wall insulation, thicker curtains.

Question 27

how does cavity wall insulation work?

Answer 27

it reduces heat transfer by convection because pockets of air are trapped in the foam.

Question 28

how does loft insulation work?

Answer 28

reduces heat transfer by conduction.

Question 29

how do you calculate payback time?

Answer 29

initial cost Divided by annual saving

Question 30

what is meant by a U-value?

Answer 30

they measure how effective a material is as an insulator

Question 31

what is meant by specific heat capacity?

Answer 31

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

Question 32

how do work out specific heat capacity?

Answer 32

Energy transferred (J) = mass (kg) X specific heat capacity (J/kg) X temperature change (‘c)

Question 33

what does convection take place in?

Answer 33

liquids & gases

Question 34

why can can’t convection take place in solids?

Answer 34

because the particles cannot move