energy transfer by heating-p2

Question 1

What is conduction?

Answer 1

Conduction is the process where vibrating particles transfer energy to neighboring particles.

Question 2

The process of conduction?

Answer 2

Energy transferred to an object by heating is transferred to the thermal store of the object. This energy is shared across the kinetic energy stores of the particles in the object. The particles in the part of the object being heated vibrate more and collide with each other. These collisions cause energy to be transferred between particles’ kinetic energy stores. This is conduction.
The process continues throughout the object until the energy is transferred to the other side of the object. Its then usually transferred to the thermal energy store of the surroundings.

Question 3

What is thermal conductivity?

Answer 3

Thermal conductivity is a measure of how quickly energy is transferred through a material in this way. Materials with a high thermal conductivity transfer energy between their particles quickly.

Question 4

Why do good insulators have to be materials with low thermal conductivity?

Answer 4

So energy transfer through them is as low as possible

Question 5

The energy transfer per second through a layer of insulting material depends on?

Answer 5

• the temperature difference across the material
• the thickness of the material
• the thermal conductivity of the material

Question 6

How can you reduce energy transfer?

Answer 6

• The thermal conductivity of the insulating material should be as low as possible
• the thickness of the insulating material should be as thick as practically possible

Question 7

What is convection?

Answer 7

Convection is where energetic particles move away from hotter to cooler regions.

Question 8

some info about infrared radiation(you are doing great, keep it up!!)

Answer 8

• All objects are continuously emitting and absorbing infrared radiation
• Infrared radiation is emitted from the surface of the object.
• Some colours and surfaces absorb and emit radiation better than others. For example, a black surface is better at absorbing and emitting radiation than a white one, and a matt surface is better at absorbing and emitting radiation than a shiny one.

Question 9

info about how much infrared radiation an object emits based on its temperature?

Answer 9

• The hotter an object is, the more infrared radiation it radiates in a given time
• An object that’s hotter than its surroundings emits more IR radiation than it absorbs as it cools down(e.g a cup of tea left on a table). And an object that’s cooler than its surroundings absorbs more IR radiation than it emits as it warms up(e.g a cold glass of water on a sunny day)
• Objects at a constant temperature emit infrared radiation at the same rate as they are absorbing it

Question 10

What is a black body radiation?

Answer 10

The radiation emitted by a perfect black body. No other object emits or absorbs radiation as effectively as a black body

Question 11

What is a perfect black body?

Answer 11

A perfect black body is an object that absorbs all of the radiation that hits it. No radiation is reflected or transmitted.

Question 12

Why are black bodies the best emitters of radiation?

Answer 12

As good absorbs are also good emitters, the perfect black bodies are the best possible emitters of radiation.

Question 13

What does the intensity and distribution of the wavelengths emitted by an object depend on?

Answer 13

The objects temperature
As the temperature of an object increases, the intensity of every emitted wavelength increases.
However the intensity increases more rapidly for shorter wavelengths than longer wavelengths. This causes the peak wave length to decrease.

Question 14

What does the overall temperature of the earth depend on?

Answer 14

Depends on the amount of infrared radiation it reflects, absorbs and emits

Question 15

Why does the temperature go up during the day?

Answer 15

During the day, lots of radiation is transferred to the earth from the Sun and absorbed. This causes an increase in local temperature.

Question 16

Why does the temperature go down at night?

Answer 16

At night, less radiation is being absorbed than is being emitted, causing a decrease in local temperature.
Overall, the temperature of the Earth stays fairly constant.

Question 17

Why does changes to the atmosphere cause a change to the Earth’s temperature?

Answer 17

If the atmosphere starts to absorb more radiation without emitting the same amount, the overall temperature will rise until absorption and emission are equal again.

Question 18

What affect do greenhouse gases have on earth’s temperature?

Answer 18

Greenhouse gases, such as carbon dioxide are good absorbers of radiation. That’s why adding more of them to the atmosphere causes the earth’s atmosphere to warm up as more radiation is absorbed by the atmosphere and less is emitted back into space.

Question 19

What is specific heat capacity?

Answer 19

Specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1*C

Question 20

What is the formula for specific heat capacity?

Answer 20

energy transferred=mass x specific heat capacity x temperature change

Question 21

Explain the required practical for specific heat capacity?

Answer 21

• To investigate a solid material(e.g copper), you’ll need a block of the material with two holes in it(for the heater and thermometer to go through)
• Measure the mass of the block, then wrap it in an insulating layer to reduce the energy transferred from the block to the surroundings. insert the thermometer and heater.
• Measure the initial temperature of the block and set the potential difference of the power supply to 10V. Turn on the power supply and start a stopwatch.
• When you turn on the power, the current in the circuit does work on the heater, transferring energy electrically from the power supply to the heater’s thermal energy store. This energy is then transferred to the materials thermal energy store by heating, causing the material’s temperature to increase.
• As the block heats up, use the thermometer to measure its temperature e.g every minute. Keep an eye on the ammeter- the current through the circuit shouldn’t change.
• When you have collected enough readings, turn off the power supply.
• You can repeat this experiment with different materials to see how their specific heat capacities compare.

Question 22

Explain the required practical to investigate the effectiveness of different insulators?

Answer 22

-Boil water in a kettle. Pour some of the water into a sealable container(e.g a beaker and lid) to a safe level. Measure the mass of the water in a container.
-Use a thermometer to measure initial temperature of the water
-Seal the container and leave it for 5 minutes. Measure this time using a stopwatch.
-Remove the lid and measure the final temperature of the water
-Pour away the water and allow the container to cool to room temperature.
-Repeat this experiment but wrap the container in a different material(foil, newspaper) once it has been sealed. Make sure you use the same mass of the water each time.
You could also investigate how the thickness of the material affects the temperature change of water.
You should also find that the thicker the insulating layer, the less energy is transferred and the smaller the temperature change of the water.

Question 23

What are a few things you can do to prevent energy loss through heating?

Answer 23

Have thick walls that are made from a material with a low thermal conductivity. The thicker the walls and the lower their thermal conductivity, the slower the rate of energy transfer will be.

Question 24

How can you use thermal insulation in your house to prevent heat loss?

Answer 24

• Some houses have cavity walls, made up of an inner and outer wall with an air gap in the middle. The air gap reduces the amount of energy transferred by conduction through the walls. Cavity wall insulation, where the cavity wall air gap is filled with foam, can also reduce energy transfer by convection in the wall cavity.
• Loft insulation can be laid out across the loft floor and ceiling. Fibreglass wool is often used which is a good insulator as it has pockets of trapped air. Loft insulation reduces energy loss by conduction and also helps prevent convection currents being created.
• Double glazed windows work in the same way as cavity walls- they have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows.
• Draught exculders around doors and windows reduce energy transfers by convection.

Question 25

How can solar panels help homes?

Answer 25

Heating a home using electricity or gas can be expensive. Solar panels absorb infrared radiation from the Sun and are used to generate electricity directly or to heat water directly. In the North, a solar panel is usually fitted on a roof that faces south so that it absorbs as much infrared radiation from the Sun as possible.