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Energy - Heating and Insulating

This GCSE Physics Energy quiz takes a look at heating and insulating. Energy efficiency in buildings usually involves using thermal insulation to hold in the heat. Heating and insulating buildings has become a major agenda for many mainstream politicians. This has resulted in various projects allowing home owners to obtain low cost insulation as the government recognises that not only will this help save money, but also reduce environmental emissions as less fuel needs to be burnt to heat homes. You may have heard people saying 'close that door and keep the cold out'. This is incorrect as heat only flows from higher temperatures to lower temperatures. Cold doesn't move, cold is NOT a form of energy. It would be more accurate to say '... keep the cold air out'.

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One source of heat loss from buildings is draughts. Cold air coming in from the outside needs to be heated up, otherwise the inside of the house would be at the same temperature as the outside. This uses energy from the heating system and reduces the overall efficiency of the house. As the cold air comes in, it means that warm air is also leaving the building somewhere. Some hi-tech homes are completely sealed to prevent draughts, incoming fresh air from the outside is controlled by using a ventilation system. To prevent the loss of energy to the outside, these usually include an efficient heat exchanger. This transfers the heat from the outgoing air to the air coming in so that the house does not need extra heating.

You will already have studied insulating homes at KS3; there are a lot of similarities with the KS4 work, however, new ideas such as U-values and payback time are introduced as well as revising methods of insulation. U-values are a measure of how well heat can travel through a material so lower U-values are associated with better insulators. The figure is a measure of how many watts of heat energy pass through a metre squared divided by the temperature difference between the opposite sides of the insulating material. In order to be able to compare U-values directly, the materials are measured under standard conditions with carefully controlled air humidity and wind conditions.

You will have met many different types of insulation but the thing that most have in common is that they contain trapped gases, usually air. This is because gases are very poor conductors of heat. When they are trapped, it prevents them from transferring heat by convection. Most heat leaves a building by being conducted through the solids used to construct it. Some heat leaves by convection (draughts) and a small proportion leaves by radiation - all objects above absolute zero emit (give off) infra-red (heat) radiation.

The largest heat loss is through the walls and the roof as these form the largest area of a building. These are the two areas that it pays to concentrate on when planning to insulate a house. Newly built houses have insulation planned as part of the design. Older houses have solid walls and it is most efficient to insulate the outside of these, although most people choose to add insulation to the inside as it is easier and cheaper. Houses built in the second half of the twentieth century and more recently usually have cavity walls. These help to keep houses both warmer and drier with less heating than solid walled houses. Adding insulation into the cavity keeps even more of the heat in, reducing energy consumption for heating even more.

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  1. What are the units of specific heat capacity?
    You should have eliminated answers 2 and 3 immediately as the symbol for kilograms is wrong (it should never be written with a capital 'K' or have an 's' added at the end)
  2. If a material is a good insulator, what size U-Value will it have?
    A lower value means less heat passes through the material and it is therefore a good insulator
  3. What do U-Values measure?
    They are a measure of how much energy can pass through an insulator and are measured using a standard set of conditions so that they can be easily compared
  4. What was the change in temperature of a material with a specific heat capacity of 1,000 J kg-1 oC-1, a mass of 2 kg which absorbed 500 joules of energy?
    Did you try working it out in your head first or did you reach straight for the calculator (after rearranging the equation)?
  5. What is specific heat capacity?
    Materials with high specific heat capacities can be used to store heat when it is available to be released at a later time
  6. Calculate the specific heat capacity of a material whose mass is 1 kg which required 300 J of energy in order to be heated from 1oC to 5oC.
    Being able to rearrange formulas is a crucial skill that you will need to have for any exam
  7. A solar panel that contains water which is heated by radiation from the sun can be used for what purposes?
    Solar energy can be used to obtain heat and electricity. Because the energy used comes from the Sun, after installation of the solar panels, it is free
  8. Which of the following formulas is used to calculate specific heat capacity?
    It is used to calculate how much energy would be needed to heat a substance up to a specific temperature, but you will often be required to rearrange it to carry out calculations on the higher tier paper
  9. If a wall has a high U-value, will it allow more or less heat to flow through it than a wall with a low U-value?
    U-values are simply a measure of how much heat can pass through a material under the same conditions
  10. How much energy is required to heat a block of material of mass 4 kg by 10oC whose specific heat capacity is 800 J kg-1 oC-1?
    You should be able to do this in your head ~ 10 times 800 is 8000, multiply that by 4 ~ 4 x 8 is 32, so the answer must be 32,000. If you practise working out calculations in your head as often as you can, then during the exam, it can act as a check on what you have worked out on your calculator

Author: Martin Moore

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