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Physics - Heating and Insulating Buildings (AQA)
Having a well insulated home will save money on heating bills.

Physics - Heating and Insulating Buildings (AQA)

The transfer of heat (thermal) energy is studied in GCSE Science. This is one of eight quizzes on that topic and it looks specifically at some ways of heating and insulating buildings in order to save both energy and money.

Keeping the warmth inside a home is an important consideration for many people. The architect who designs buildings needs to know how good different materials are at insulating them, so they can work out what sort of heating system will work the best. For whoever pays the bills, knowing where the most heat is being lost, and how to slow down that heat loss, will help them to save money on their heating bills. For anyone keen on environmental issues and keeping their carbon footprint as low as possible, knowing which environmentally friendly materials are the best insulators is essential.

This is the point that U-values step in! These are a measure of how fast heat can pass through a material. Building materials have been tested and their U-values worked out. A lower U-value indicates that heat only passes through the material slowly, therefore the material is better at insulating than one with a high U-value, and vice-versa. You don't need to know any specific U-values or how they are calculated.

Heating well insulated buildings requires less energy overall and so saves money on the heating costs. It also helps to reduce the emissions of carbon dioxide. Unless the building is heated by a non-polluting supply of electricity or by geothermal energy, somewhere down the line carbon dioxide will be released into the air. Let's take for example using electric storage heaters. These transfer electrical energy into heat, taking their electricity from the National Grid. Most National Grid electricity is produced in conventional power stations which release large quantities of carbon dioxide into the air. Using gas or oil fired central heating systems puts carbon dioxide into the air directly.

Using wood fired heating is more environmentally friendly as the carbon dioxide released is called current carbon. In other words, it is carbon from the present time rather than being from millions of years in the past, as happens when burning fossil fuels. For hot water, solar panels on the roof of a building use the Sun's heat instead of burning fuels.

What is meant by payback time in the context of insulating a building?
The time taken to pay off any loans that you needed
How long it takes you to get your revenge on the builder after they have done a poor job
How long it takes to get a grant from the government for the insulation work
A measure of how cost-effective the insulation is
Payback time (years) = cost of installation (£) ÷ savings per year in fuel costs (£). It works for any energy saving situation, for example swapping conventional lightbulbs with low energy bulbs or LED lighting. The shorter the payback time, the more cost-effective it will be
During the day, the Sun transfers energy to an outdoor swimming pool. The mass of water in the pool is 5,000 kg. The specific heat capacity of water is 4,200 J/kg °C. How much energy needs to be supplied to increase the water temperature by 5oC?
105,000,000 J
10.5 kJ
21,000,000 J
210 kJ
The correct equation for this calculation is Energy = Mass x Specific heat capacity x Temperature change. In the exam you should have a data sheet with a list of equations but it is still a good idea to memorise as many of the equations as you can
How do solar hot water panels work?
Heat radiation from the sun warms the water which is then pumped to a storage tank
The light from the Sun is used to generate electricity that powers a water heater
They absorb heat from the air
They use heat escaping through the roof from inside the house to heat the water
Heat reaches the Earth from the Sun in the form of infrared radiation. The water heating tubes are coloured black as that is the best colour for absorbing infrared
The best insulators have what sort of U-value?
A low U-value
A high U-value
A constant U-value
A variable U-value
The U-value is a measure of how many watts can pass through one square metre of the material if there is a 1oC temperature difference from one side to the other, so the best insulators have low U-values. A lower U-value means that fewer watts are getting through in any given period of time than would in a material with a higher U-value
At night, a storage heater transfers electrical energy into thermal energy which is stored. During the day, the heat is released to warm the room. Which of the following would store the most thermal energy per kg?
Aluminium - specific heat capacity 913 J/kgoC
Water - specific heat capacity 4,200 J/kgoC
Oil - specific heat capacity 3,850 J/kgoC
Concrete - specific heat capacity 880 J/kgoC
Of these materials only oil is actually used - this question is testing your understanding of specific heat capacity. In reality, storage heaters have a core of specially designed high density thermal blocks. These are heated by electric elements using cheap rate electricity during the night. These blocks are preferred instead of water or oil, even though they have a lower specific heat capacity. They are much more dense and can store more thermal energy without the risk of a leak. Oil storage heaters do not work as effectively as those fitted with the thermal blocks
To heat the water in a domestic hot water storage tank from 42°C to 50°C, an immersion heater transfers 4,536 kJ of energy to the water. How much water is in the tank? The specific heat capacity of water is 4,200 J/kgoC
100 kg
135 kg
0.135 kg
10 kg
You need to rearrange the specific heat equation to isolate the mass on the left hand side and remember to convert kJ to J
What are U-values?
A measure of the thickness of an insulator
A measure of the temperature of an insulator
A measure of how fast heat can pass through an insulator
A measure of the surface area of an insulator
No material is a perfect insulator - U-values tell you the rate at which heat energy can get through
If it costs £2,000 to insulate the walls and roof of a house, how long will the payback time be if it saves £250 per year?
2 years
4 years
8 years
16 years
There are other considerations to take into account when insulating a building, such as improved comfort. It's not just about the money
A homeowner has part of the outside brick wall of her house demolished and fits double-glazed glass doors in the gap. The U-value of the wall was 0.4 and the U-value of glass doors is 1.8. What does this mean?
Her house is now better insulated
She will save money on heating bills
More heat will be lost from the house
There will be no change to the amount of heat lost from the house
The higher U-value means that the new doors are less insulating than the original wall, so she will need to use more energy to keep the room as warm as it was before
Which of the following is not a good reason for having solar hot water panels fitted?
They do not release any gases into the air as they heat the water
They reduce the bill for heating and hot water
On cloudy days, the water is not very hot
They work all year round
On cloudy days the temperature of the water would need boosting using some other method of heating. There are other disadvantages too, for example the savings you make on your energy bills are quite small and, even on a small house, you need quite a large area of panels on a south facing roof to get sufficient hot water
You can find more about this topic by visiting BBC Bitesize - Energy and heating - AQA

Author:  Kev Woodward

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