P1.1

Question 1

All objects…

Answer 1

…emit and absorb infrared radiation

Question 2

The hotter an object…

Answer 2

The more infrared radiation it radiates in a given time

Question 3

Dark Matt surfaces =

Answer 3

Good absorbers and good emitters

Question 4

Light stingy surfaces =

Answer 4

Poor absorbers and poor emitters but good reflectors

Question 5

Solids…

Answer 5

…strong forces of attraction
Little energy
Vibrate in fixed position

Question 6

Liquids…

Answer 6

…weaker forces of attraction
More energy
move about at random with low speeds

Question 7

Gases…

Answer 7

…almost no forces
More energy
Move in random direction with high speeds

Question 8

What does conduction happen in?

Answer 8

Solids

Question 9

What does convection happen in?

Answer 9

Liquids and gases

Question 10

What does radiation happen in?

Answer 10

Solids liquids and gases

Question 11

Describe conduction

Answer 11

Vibrating particles pass on extra k.e to neighbouring particles

Question 12

What are conductors?

Answer 12

Materials with particles very close together so conduct heat fastest

Question 13

What are insualtors?

Answer 13

Materials which conduct heat more slowly because particles have spaces between them

Question 14

Why are metals good conductors?

Answer 14

They have free electrons which collide with other free electrons and transfer energy

Question 15

Is condition fastest in a short fat rod or a long thin rod?

Answer 15

faster conduction in a short fat rod

Question 16

Describe convection

Answer 16

Air or water is heated
Expands and rises because it’s less dense
Particles with more k.e collide with colder particles and lose energy as they transfer it
Cooler water sinks because it’s more dense
Then it repeats

Question 17

Describe condensation

Answer 17

Gas to liquid
As a gas cools it slows down and loses k.e so particles are pulled together to form a liquid
Water vapour condenses when it hits a cool mirror

Question 18

How to increase the rate of condensation?

Answer 18

Lower gas temp
Lower temp of surface that gas hits
Higher density
Less airflow

Question 19

Describe evaporation

Answer 19

Liquid to gas
Particles leave a liquid if they are traveling in the right direction and with enough energy/speed
Faster/hottest particles will leave first so temp of liquid will decrease and energy of remaing particles will decrease

Question 20

How to increase the rate of evaporation?

Answer 20

Higher temp
Lower density
Larger s.a
More airflow

Question 21

What factors increase the rate at which energy is transferred by heating?

Answer 21

Higher surface area and lower volume
The material the object is made - conductor or insulator
The surface the object is in contact with - conductor or insulator

Question 22

How is a room heated by a radiator?

Answer 22

By convection currents and they have a large surface area

Question 23

Why do cars have fins?

Answer 23

To increase the s.a so heat is radi rated quicker and the engine cooks

Question 24

What are heat sinks?

Answer 24

Transfer heat away from objects they’re in contact with

They have fins and a large s.a to emit heat asap

Question 25

Describe the vacuum flask

Answer 25

• Double walled with a vacuum between the walls - stopping conduction and convection
• Silvered walls to reduce heat loss by radiation
• Insulating foam minimising heat loss by conduction
• A stopper made of plastic and filled with cork or foam to reduce heat conduction

Question 26

How do humans and animals control temperature when it’s cold?

Answer 26

Hairs stand up to trap a layer of insulating air limiting convection
Arctic animals have fur and smaller ears to minimise heat loss by radiation

Question 27

How do humans and animals control temperature when it’s hot?

Answer 27

Blood flows to skins surface and is lost by radiation

Animals have larger ears in warmer climates to lose heat by radiation eg desert fox

Question 28

How can energy be transferred?

Answer 28

By work or heating

Question 29

How to reduce heat transfer in homes?

Answer 29

Cavity wall insulation stopping convection, conduction and radiation
Loft insulation stopping conduction and convection
Draft excluders reducing convection
Hot water jacket reducing conduction and convection
Thick curtains and carpets reducing conduction and convection
Foil behind radiators reducing conduction and radiation
Double glazing creating a vacuum and reducing conduction and convection

Question 30

The bigger the temp differences between an object and its surrounding…

Answer 30

…the faster the rate at which energy is transferred by heating

Question 31

What do u-values measure?

Answer 31

How effective a material is as an insulator

Question 32

The lower the U-value…

Answer 32

…the better the material is as an insulator

Question 33

How do solar panels work?

Answer 33

Contain water which is heated by radiation from the sun
Often painted black which is a good absorber
They can then heat building or be used as hot water

Question 34

What does the specific heat capacity measure?

Answer 34

The amount of energy required to change the temperature of one kilogram of the substance by one degree

Question 35

What is the specific heat capacity of water?

Answer 35

4200j/kg degrees c

Question 36

Do the materials used in heaters have a high or low specific heat capacity?

Answer 36

High so they can store large amounts of energy

Question 37

Why does water have a high specific heat capacity?

Answer 37

So it can be pumped around in pipes for central heating

Question 38

How do electric storage heaters work?

Answer 38

Store heat using concrete or bricks at night and release it during the day

Question 39

How do oil filled heaters?

Answer 39

Lower specific heat capacity than water meaning it’s not S good
But oil has a higher boiling point so can reach higher temperature