Energy Tranfer By Heating

Question 0

Do all objects emit infra red

Answer 0

Yes

Question 1

How can we detect infrared radiation

Answer 1

It feels warm

Question 2

How does the temp of an object affect the rate of infrared emission

Answer 2

The hotter the object is the more infrared it emits at any one given time

Question 3

What is a vacuum

Answer 3

A region that doesn’t contain anything at all, not even gas particles.

Question 4

Can infrared travel through a vacuum

Answer 4

Yes

Question 5

Does the transfer of infrared involve particles

Answer 5

No particles are not needed

Question 6

What are the best absorbers

Answer 6

Dark, matt surfaces

Question 7

Why are houses in hot countries painted white

Answer 7

So the houses absorb less heat and are therefore cooler

Question 8

What is meant by dull, matt surfaces are good emitters

Answer 8

An object painted matt black will transfer energy and cool down quickly

Question 9

Why are pipes on a fridge painted black

Answer 9

Black surfaces are the best emitters of infrared so they will cool down quickly

Question 10

What surfaces are good reflectors

Answer 10

Shiny surfaces

Question 11

How is the arrangement of particles in a liquid different to those in a solid

Answer 11

In a liquid the particles are in contact with each other but are not held in fixed positions, like solids

Question 12

How is the arrangement of particles in a gas different to those in a liquid

Answer 12

The particles in a gas are much further away and move faster than those in a liquid

Question 13

Is the density of a gas much less or much more than a solid or liquid

Answer 13

Much less

Question 14

Which two states make poor conductors

Answer 14

Gas and liquid

Question 15

How is heat transferred through a solid

Answer 15

One end of the solid is heated, the particles gain kinetic energy and vibrate passing on the energy to its neighbouring particles

Question 16

What happens to a metals free electrons

Answer 16

They gain kinetic energy and move through the metal, transferring energy by colliding with particles

Question 17

Why is the saucepan made of metal and the handle of a saucepan wood

Answer 17

Because the metal is a good conductor and will heat the pain quickly but the wood is a poor conductor so the handle doesn’t heat up and burn the user

Question 18

What are poor conductors called

Answer 18

Insulators

Question 19

Why are materials that trap air good insulators

Answer 19

Air is a poor conductor so materials that trap air are good insulators

Question 20

In which states does convection occur

Answer 20

Liquid and gas

Question 21

How does a convection current occur

Answer 21

Fluid is heated, becomes less dense and rises. The warm fluid is replaced by cooler, denser fluid. This transfers energy through out the fluid

Question 22

Why doesn’t convection currents occur in solids

Answer 22

Particles in solids are held in fixed position, so they cannot flow.

Question 23

Name a process not on land that is caused by convection

Answer 23

Offshore and onshore breezes

Question 24

How does evaporation take place

Answer 24

The most energetic particles leave the surface of the liquid and enter the air. Therefore the average kinetic energy in the remaining liquid is less so the temperature decrease. This means evaporation causes cooling

Question 25

What are the factors that increase the rate of evaporation

Answer 25

• Increase surface area
• increase the temperature of the liquid
• crating a draught across the surface of the liquid

Question 26

How is the rate of condensation increased

Answer 26

• reducing the surface temperature

- increasing surface area

Question 27

Hat effect does the temp difference between an object and it’s surroundings have on the rate of energy transfer

Answer 27

The greater the difference between the object and it’s surroundings the larger the rate of energy transfer

Question 28

What does the rate at which energy is transferred depend on

Answer 28

• the materials the object is in contact with
• the objects shape
• the objects surface area

Question 29

What do you use to maximise the rate of energy transfer

Answer 29

• good conductors
• painted dull black
• have the air flow around them maximised

Question 30

Why does painting an object black maximise the rate of energy transfer

Answer 30

Because black surfaces are good emitters

Question 31

Why do you sometimes want to minimise the rate of energy transfer

Answer 31

To keep things warm

Question 32

To minimise the rate of energy transfer what things do you want

Answer 32

• good insulators
• shiny surfaces white
• prevent convection currents by trapping air in pockets

Question 33

What is the specific heat capacity

Answer 33

The amount of energy required to raise the temperature of a 1kg substance by 1 degree

Question 34

If the specific heat capacity increases what does that mean about the energy required for each energy

Answer 34

It increases

Question 35

What affects the specific heat capacity

Answer 35

• the mass of an object

- the amount of energy supplied to an object

Question 36

How can you reduce energy loss in homes

Answer 36

• cavity walls
• loft insulation
• draught excluders
• double glazing
• aluminium foil behind radiators

Question 37

What does a u value mean

Answer 37

It tells us how much energy per second passes through a material

Question 38

What kind of u- value tells us that the material is a better insulator

Answer 38

The lower the number, the better the insulator.

Question 39

How are solar panels heated

Answer 39

By radiation from the sun

Question 40

When do solar panels not work

Answer 40

At night

Question 41

Why are the pipes in solar heating panels painted black

Answer 41

Because black in the best absorber of infrared