P2 - Energy Transfer by Heating

Question 1

What is black body radiation?

Answer 1

the radiation emitted by a perfect black body (a body that absorbs all the radiation that hits it)

Question 2

What is infrared radiation?

Answer 2

electromagnetic waves between visible light and microwaves in the electromagnetic spectrum

Question 3

What is specific heat capacity?

Answer 3

the amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C. (J/KG °C)

Question 4

What is thermal conductivity?

Answer 4

property of a material that determines the energy transfer through it by conduction

Question 5

What is thermal insulation?

Answer 5

Thermal insulation is the process of the reduction of heat transfer

Question 6

What is infrared radiation?

Answer 6

electromagnetic waves between visible light and microwaves in the electromagnetic spectrum

Question 7

What objects emit and absorb infrared radiation?

Answer 7

all objects

Question 8

How does the temperature of an object affect the amount of infrared radiation it emits?

Answer 8

the higher the temperature of an object, the more infrared radiation it emits in a given time

Question 9

a body at a constant temperature will ….

Answer 9

stay at a constant temperature if it absorbs infrared radiation at the same rate it emits it. It will also emit radiation across a continuous range of wavelentgths

Question 10

What is a perfect black body?

Answer 10

A perfect black body is an object that absorbs all the radiation that hits it (ie does not reflect or transmit it)

Question 11

What is the best possible emitter of infrared radiation?

Answer 11

a perfect black body

Question 12

What is the radiation emitted from a perfect black body called?

Answer 12

black body radiation

Question 13

If the temperature of the body is increased, what happens to the intensity of the radiation?

Answer 13

the intensity of the radiation sir greater at every wavelength

Question 14

As an object increases in temperature, what happens to the peak intensity of radiation?

Answer 14

the peak intensity wavelength decreases

Question 15

Why does the peak intensity wavelength decrease as temperature is increased?

Answer 15

As the temperature of an object is increased, the intensity of radiation emitted increases across all wavelength. However, the intensity of radiation increases more rapidly at shorter wavelengths than at longer wavelengths, this causes the peak intensity wavelength to decrease!

Question 16

How does an object increase in temperature?

Answer 16

it absorbs infrared radiation faster than it emits it

Question 17

Why do rescue team use a light-coloured, shiny blanket to keep accident survivors warm?

Answer 17

a light, shiny surface emits less radiation than a dark, matt surface. This keeps the patient warm as less infrared radiation is emitted

Question 18

What is the equation for Specific heat capacity?

Answer 18

SHC = Energy / Mass x ΔTemperature

Question 19

What is the equation for energy?

Answer 19

power x time

Question 20

What is the equation for power?

Answer 20

current x voltage

Question 21

What is current measured with?

Answer 21

An Ammeter

Question 22

What is current measured in?

Answer 22

Amperes (Amps)

Question 23

What is voltage measured with?

Answer 23

A voltmeter

Question 24

What is voltage measured in?

Answer 24

volts

Question 25

What is a current?

Answer 25

An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor

Question 26

What is voltage?

Answer 26

Voltage is the difference of electrical potential between two points of an electrical circuit

Question 27

Describe the method for investigating sheets of materials as insulators

Answer 27

1) Set up your containers: leave one unwrapped, and wrap each of the others in a different material, using elastic bands or tape to hold the material in place. Try to make the different wrappings roughly the same thickness.
2) Prepare lids for the containers, made out of the same material as the wrapping if possible, otherwise made from aluminium foil or cling film.
3) Make a hole in each lid which is just big enough for the thermometer to fit through.
4) Use the measuring cylinder to pour equal amounts of hot water into each container.
5) Put the lids onto the containers, with a thermometer fitted through each lid so that it rests near the bottom of the water.
6) Start the stopwatch, and measure the starting temperature of the water.
7) After 15 minutes, use the thermometer to gently stir and then measure the temperature of the water in each beaker.
8) record your results in a suitable table or graph
9) if you have time, repeat the experiment and get a mean average for each material to get more accurate results

Question 28

What is a thermal conductor?

Answer 28

A thermal conductor is a material that allows thermal energy to move through it easily. All metals are good thermal conductors

Question 29

What is a thermal insulator?

Answer 29

A thermal insulator is a material that does not allow thermal energy to move through it easily. Materials such as fibreglass and wool are good thermal insulators because they trap air

Question 30

What does the rate of thermal energy transfer through a material depend on?

Answer 30

° The temperature difference across the material
° The thickness of the material
° The thermal conductivity of the material

Question 31

How do you reduce the rate of thermal energy transfer?

Answer 31

° the insulating material should have as low a thermal conductivity as possible
° the insulating material should be as thick as possible

Question 32

What does the temperature of the earth depend on?

Answer 32

° The rate at which the radiation from the sun is reflected or absorbed by earths atmosphere, and the earths surface
° the rate at which radiation is emitted from the earths surface, and from the earths atmosphere, into space

Question 33

Describe how greenhouse gases warm the earth

Answer 33

Infrared radiation from the sun warms the ground. The ground becomes warm and emits longer-wavelength infrared radiation. Greenhouse gas molecules absorb and re-emit the longer-wavelength infrared radiation back to the ground. This process makes the earth warmer than if these gases were not in the atmosphere

Question 34

What is the equation for the rate of heat flow across a plate of material?

Answer 34

Q = kA(ΔT/Δx)

Heat flow = (Thermal conductivity x cross sectional area of material) x (temperature difference / thickness of material)

Question 35

What is temperature?

Answer 35

The measure of the average kinetic energy of the random motion of molecules on the material

Question 36

Describe the method the measure specific heat capacity

Answer 36

1) Obtain a 1kg block of a metal with 2 holes in it for the thermometer and the heater
2) Use a pipette to place a small amount of water in the larger hole, then insert the heater
3) Connect the power pack, heater, and ammeter in series
4) Connect the voltmeter in parallel
5) Use a pipette to place a small amount of water in the smaller hole then insert the thermometer
6) Turn the power pack to 6V then switch it on
7) Record the ammeter and voltmeter readings. These should not change during the experiment
8) Record the temperature reading every 1 minute for 18 minutes
9) Calculate the power of the heater in watts by multiplying the ammeter reading by the voltmeter reading
10) Calculate the work done by the heater by multiplying the time in seconds by the power of the heater
11) If you have time repeat the experiment to get a mean average for a more accurate result
12) Record the data in an appropriate graph and/or table
13) Calculate the specific heat capacity of the metal by dividing the total energy transferred by the heater by the temperature change of the block

Question 37

How does a Storage heater work?

Answer 37

A storage heater uses electricity at night to heat special bricks or concrete blocks in the heater. Energy transfer from the bricks keeps the room warm. The bricks have a high specific heat capacity, so they store lots of energy. They warm up slowly when the heater element is on, and cool down slowly when it is off.

Question 38

Name 5 ways in which people can reduce the heating bills in their houses

Answer 38

Fibreglass loft insulation, Cavity wall insulation, Aluminium foil behind radiators, Double glazed glass, and Thick bricks with low thermal conductivity

Question 39

How does fibreglass loft insulation help reduce the heating bills in peoples houses?

Answer 39

Fibreglass loft insulation help reduce the heating bills in peoples houses by reducing the rate of energy transfer through the roof. The air between the fibres helps reduce the energy transfer by conduction

Question 40

How does Cavity wall insulation help reduce the heating bills in peoples houses?

Answer 40

Cavity wall insulation help reduce the heating bills in peoples houses by reducing the rate of energy transfer through the outer walls of the house. The insulation is pumped in the wall cavity. It is a better insulator than the air it replaces. It traps the air in small pockets, reducing the rate of energy transfer by conduction.

Question 41

How does Aluminium foil behind radiators help reduce the heating bills in peoples houses?

Answer 41

Aluminium foil behind radiators help reduce the heating bills in peoples houses by reflecting the radiation away from the wall and back into the room. This reduces the rate of energy transfer by radiation

Question 42

How does Double glazed glass help reduce the heating bills in peoples houses?

Answer 42

Double glazed glass help reduce the heating bills in peoples houses as they are 2 panes with dry air or a vacuum between the panes. The thicker the glass the lower the thermal conductivity is, the slower the rate of transfer of energy through it by conduction. Dry air is a good insulator, so it reduces the rate of energy transfer by conduction. A vacuum also prevents energy transfer by convection

Question 43

How do thick bricks with low thermal conductivity help reduce the heating bills in peoples houses?

Answer 43

If the external walls of a warm building have thicker bricks and lower thermal conductivity, the rate of transfer of energy from inside of the building will be lower and the cost of heating will be less

Question 44

How do solar cell panels generate electricity?

Answer 44

Solar cell panels absorb infrared radiation from the sun and use it to generate electricity directly

Question 45

How do solar heating panels heat water?

Answer 45

Solar heating panels absorb infrared radiation from the sun and use it to heat water directly

Question 46

What is a solar cell panel?

Answer 46

A solar cell panels is a solar panel that absorbs infrared radiation from the sun and uses it to generate electricity directly

Question 47

What is a solar heating panel?

Answer 47

A solar heating panel is a solar panel that absorbs infrared radiation from the sun and uses it to heat water directly

Question 48

On what side of the roof are solar panels fitted in the northern hemisphere and why?

Answer 48

The south side so it can absorb as much infrared radiation as possible

Question 49

Why are the pipes that contain the water in a solar heating panel often painted black?

Answer 49

The colour black is the best absorber of heat. This is because black items absorb all the wavelengths of light and do not reflect any back. This makes them absorb more hat as they do not reflect any of the radiation back