Core Science Keeping Buildings Warm

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Miles Hart
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Core Science Keeping Buildings Warm Name Homework Redhill School Q1. The diagram shows where heat is lost from a house that is not insulated. (a) (i) Through which part of the house is most heat lost?

1 Core Science Keeping Buildings Warm Name Homework Redhill School Q1. The diagram shows where heat is lost from a house that is not insulated. (a) (i) Through which part of the house is most heat lost? How can the heat loss through the windows be reduced? (b) A homeowner wants to reduce her energy bills and make her home more energy efficient. The table shows five ways this could be done. The table also shows how much money each way would save the homeowner each year. Cost Money saved each year Installing loft insulation Fitting draught-proofing Installing cavity wall insulation Adding a hot water tank jacket Using energy efficient light bulbs Page 1

2 (i) Which one of the five ways of reducing energy bills would reduce the yearly energy bill the most? This year the homeowner has only got 60 to spend to improve the energy efficiency of her home. Use the information in the table to explain what the homeowner should spend this money on. (Total 5 marks) Q2. People do a number of things to reduce the energy loss from their homes. (a) Describe one thing they may do to cut down the energy loss through: (i) the roof;... the outside walls;... (iii) the glass in the windows;... (iv) gaps around the front and back doors.... Page 2

3 (b) A house is more difficult to keep warm in cold weather. What other type of weather makes it difficult to keep a house warm?... (Total 5 marks) Q3. The diagrams show the cross-section of three double glazed windows. The gap between the two sheets of glass can be filled with either air or a mixture of air and argon. The U-values for different types of double glazed windows, using different types of glass X and Y, are given in the table. Type of window 12 mm gap 16 mm gap 20 mm gap 1 Glass type X with air Glass type X with air and argon Glass type Y with air Glass type Y with air and argon (a) Which type of window, 1, 2, 3 or 4 is the least energy efficient?... Page 3

4 (b) Which two windows should be compared to decide if adding argon to the gap improves the energy efficiency of the window?... (c) A householder is going to buy new windows. The sales assistant recommends that the householder buys windows with a 20 mm gap. These windows are much more expensive than those with a 16 mm gap. It is not worth the householder paying the extra cost to buy 20 mm windows rather than 16 mm windows. Explain this in terms of energy efficiency (d) Windows are given an energy rating, from A down to G. The diagram shows the energy label from one type of double glazed window. All new double glazed windows must have an energy rating of C or above. Windows having a C rating have a U-value of 1.9. Which windows given in the table would the householder be unable to buy?... Page 4

5 (e) Glass transmits infrared radiation and visible light. The amount transmitted depends on the type and thickness of the glass. The data from tests on two different types of glass is displayed in the graph below. A homeowner has a glass conservatory built on the back of the house. The homeowner tells the builder that the inside of the conservatory should stay as cool as possible throughout the summer. Explain why the builder uses Type B glass for the conservatory (Total 7 marks) Q4. (a) The graph shows the temperature inside a flat between 5 pm and 9 pm. The Page 5

6 central heating was on at 5 pm. Redhill School (i) What time did the central heating switch off?... Closing the curtains reduces heat loss from the flat. What time do you think the curtains were closed?... Give a reason for your answer.... (b) Less heat is lost through double-glazed windows than through single-glazed windows. Page 6

Complete the following sentences by choosing the correct words from the box. Each word may be used once or not at all. conduction conductor convection evaporation insulator radiation Air is a good.

7 Complete the following sentences by choosing the correct words from the box. Each word may be used once or not at all. conduction conductor convection evaporation insulator radiation Air is a good.... When trapped between two sheets of glass it reduces heat loss by... and... (3) (c) The table gives information about three types of house insulation. Type of insulation Cost to install Money save each year on heating bills Payback time Double glazing years Loft insulation years Cavity wall insulation (i) Use the information in the table to calculate the payback time for cavity wall insulation.... Page 7

8 Explain why people often install loft insulation before installing double glazing or cavity wall insulation (Total 9 marks) Q5.Diagram 1 shows the energy transferred per second from a badly insulated house on a cold day in winter. Diagram 1 (a) (i) When the inside of the house is at a constant temperature, the energy transferred from the heating system to the inside of the house equals the energy transferred from the house to the outside. Calculate, in kilowatts, the power of the heating system used to keep the inside of the house in Diagram 1 at a constant temperature. 1 kilowatt (kw) = 1 kilojoule per second (kj/s) Power of the heating system =... kw Page 8

9 Redhill School In the winter, the heating system is switched on for a total of 7 hours each day. Calculate, in kilowatt-hours, the energy transferred each day from the heating system to the inside of the house. Use the correct equation from the Physics Equations Sheet. Energy transferred each day =... kwh (iii) Energy costs 15 p per kilowatt-hour. Calculate the cost of heating the house for one day. Cost =... (iv) The heating system is switched off at midnight. The graph shows how the temperature inside the house changes after the heating system has been switched off. Time of day Draw a ring around the correct answer in the box to complete the sentence. Between midnight and 6 am the rate of energy transfer from decreases. the house decreases then stays constant. increases. Page 9

10 Give the reason for your answer. (b) Diagram 2 shows how the walls of the house are constructed. Diagram 3 shows how the insulation of the house could be improved by filling the air gap between the two brick walls with plastic foam. Diagram 2 Diagram 3 U-value of the wall = 0.7 U-value of the wall = 0.3 (i) The plastic foam reduces energy transfer by convection. Explain why. Filling the air gap with plastic foam reduces the U-value of the wall. What is meant by the term U-value? Page 10

11 (c) A homeowner has part of the outside wall of her house removed and replaced with double-glazed glass doors. U-value of the wall = 0.3 U-value of glass doors = 1.8 Explain the effect of replacing part of the outside wall with glass doors on the rate of energy transfer from the house (Total 11 marks) Q6. (a) The diagram shows the ways in which heat energy can be transferred from an old house. Page 11

(i) Calculate the percentage of energy transferred by draughts. % energy transferred by draughts =... Complete the following sentence using one of the words from the box.

12 (i) Calculate the percentage of energy transferred by draughts. % energy transferred by draughts =... Complete the following sentence using one of the words from the box. conduction convection radiation Draughts transfer heat energy by... (iii) State one way of reducing the heat transfer by draughts.... (b) The diagram shows a section through the walls of a house built in Explain how the air cavity between the two walls reduces the heat transfer from the house Page 12

13 (c) Redhill School The table shows the installation costs and yearly savings on energy bills for different methods of insulating a house. Method of insulation Installation cost in Yearly saving on energy bills in Double glazing Loft insulation Cavity wall insulation (i) Give one reason why loft insulation is often fitted to an old house before double glazing or cavity wall insulation The time it takes for the saving on energy bills to equal the cost of installing the insulation is called the pay-back time. Calculate the pay-back time for loft insulation.... Pay-back time =... years (Total 7 marks) Q7. Warm air inside a house contains water in the form of a gas. The water condenses onto cold surfaces such as windows. This leaves liquid water on the inside of the glass. (a) Explain what happens to the particles when water changes from a gas to a liquid Page 13

14 ... Redhill School (b) Many houses in the UK have double-glazed windows. Photograph supplied by istockphoto/thinkstock If the window is double-glazed rather than single-glazed there is less condensation on the inside of the glass. Explain why (c) Double glazing can be made using two pieces of normal glass with an air gap between them. Better insulating glass (Superglaze or G-type) can be used instead of normal glass. The size of the air gap can also be increased to improve insulation. A company making double glazing provides some information about their products. Page 14

15 U-values for different types of double glazing Normal glass Superglaze G-type 6 mm air gap mm air gap mm air gap For the same size window, under the same temperature conditions, the energy loss halves if the U-value is halved. Cost of double glazing in per m 2 Normal glass Superglaze G-type 6 mm air gap mm air gap mm air gap (i) The data the double glazing company produced is checked and confirmed independently by other scientists. Suggest why it is important to confirm the data independently... A homeowner is going to replace his old single-glazed windows with new double-glazed windows. Discuss the cost of fitting double glazing using better insulating glass compared with double glazing using normal glass. Use the information given in the tables. Page 15

16 Redhill School (3) (Total 8 marks) Page 16

Q1. (a) The graph shows the temperature inside a flat between 5 pm and 9 pm. The central heating was on at 5 pm.

Q1. (a) The graph shows the temperature inside a flat between 5 pm and 9 pm. The central heating was on at 5 pm. Q. (a) The graph shows the temperature inside a flat between 5 pm and 9 pm. The central heating was on at 5 pm. (i) What time did the central heating switch off? () (ii) Closing the curtains reduces heat