1. P1 – Energy for the home
Revision lesson 1

2. Revision Lessons Does not contain all of the content for P1 – use checklists ..\P1 Energy for the home 2011\Summary and Checklists\P1 Checklist Foundation.doc ..\P1 Energy for the home 2011\Summary and Checklists\P1 Checklist Higher.doc
21/02/2019

3. Temperature and heat Temperature is a measurement of hotness.
The temperature of an object is measured in degrees celsius (°C).
Heat is a measurement of the energy of an object
Heat energy is measured in Joules (J)

4. Complete
cool high higher low quicker thermograms warm cold warm
Hot objects have a __________ temperature and usually __________ down.
Cold objects have a __________temperature and usually __________ up.
Energy will flow from a hotter object to a colder one.
The greater the temperature difference, the faster the rate of cooling will be. For eg. A hot cup of coffee would cool down faster in a _______room than in a ______ room
____________________ are pictures in which colour is used to represent temperature.
For warm objects, the __________ the temperature, the __________ they cool.

5. Specific heat capacity
The amount of energy needed to raise the temperature of something depends on:
How much there is (mass)
The temperature rise
What it is (specific heat capacity)
Energy = mass x specific heat capacity x temperature change
Calculate the energy transferred when 80kg of water is heated from 10oC to 25oC. (SHC of water = 4200)
80 x 4200 x (25-10) = J
SHC = how much energy something can store. The specific heat capacity of water is high therefore once heated it stores alot of energy, so its used for central heating
Remember water has a higher SHC than most things so it can take more heat energy (time) to increase its temperature

6. Energy
Mass x SLH
Specific latent heat
Specific latent heat is the energy needed to change the state of 1kg of a substance without changing its temperature
Specific latent heat water to stem
= j/kg
Energy = mass x specific latent heat
Calculate the energy transferred when 1.5kg of water in a kettle changes from liquid to a gas at 100oC.
1.5 x = J
Energy needed to change state, its different for all different materials

7. Energy is put into break intermolecular bonds
gas
150
100 50
-50
Boiling
point
This flat line shows where energy is being used to break the intermolecular bonds for evaporation
liquid
Melting
point
heating
solid
Time/s
heating
This flat line shows where energy is being used to break bonds – this has to be done during melting

8. Heat transfer Heat can transfer in one of three ways: Conduction
Convection
Radiation

9. Words – vibrations, electrons, solid, heated, better
Conduction
Conduction is all about when heat is transferred through a _________. The heat is passed on by ___________ in the molecules. These vibrations get BIGGER when the solid has more ENERGY (i.e. when it is being __________).
Metals are _______ conductors than non-metals. This is because the heat is carried by free ________ that can carry the energy around the metal and give it to other electrons and ions.
Heating a non-metal
Heating a metal
Words – vibrations, electrons, solid, heated, better

10. Conduction Cavity Walls
How does a cavity wall prevent heat loss from a home?
1. H____ energy reaches the interior wall
eat
2. The heat energy is c_______ through the wall
onducted
3. The air cavity between the two walls acts as an i_______ and reduces heat loss by c_______ .
nsulator
onduction

11. Side-view of double glazing
How does double glazing keep a house warmer?
Double glazing keeps a house warmer because there is a layer of a__ between the panes of glass.
Air is a poor c________, so it acts like an i_______, .
The trapped air r_______ heat loss by c_________ from a house. ir
onductor
nsulator
educes
onduction
Side-view of double glazing
insulating layer
of air

12. Convection – Key Ideas Heat transfer through liquids and gases
Heat causes particles in a fluid to: move apart → less dense → lighter → rises (and replace by cooler fluid)

13. Insert the Missing Words
Convection
Insert the Missing Words
2. On reaching the surface, the water _____ when in contact with the air
cools
3. As the water cools it becomes more ______ and sinks
1. As the water is ______ it becomes less dense and _____
heated
dense
rises
4. A cycle develops whereby warm water rises and cool water sinks, we call this a __________ current
heat
convection

14. Radiation – key facts All hot objects radiate heat.
Called infra-red radiation
Dull, dark surfaces are the best radiators and absorbers of heat
Pale, shiny surfaces are the worst radiators and absorbers of heat
Infra–red radiation can travel through a vacuum

15. Radiation
21/02/2019
Radiation is when heat moves around in electromagnetic _________ like light does. Any hot object will emit heat radiation – the hotter it is, the more radiation it emits. This type of radiation is called __________, and too much of it will cause _________. Dark, matt colours will absorb AND emit the _____ infra-red radiation, and light, shiny colours will ________ it.
The main difference with radiation is that conduction and convection could ONLY happen in solids, liquids or gases, whereas radiation will happen through an _____ _____. This is just as well, as otherwise we wouldn’t be able to get any heat from the ___.
Words – sun, reflect, infra-red, waves, most, empty space, sunburn
Anything HOT emits HEAT RADIATION – the hotter it is, the more infra red radiation it emits

16. Thought shower: Where can heat be lost from your home?:
Obviously, insulating your home can be quite expensive.
Bring out air pockets etc. Compare with styrofoam cup.

17. Reduce energy loss from homes
Roof - insulate loft; reduce conduction through ceiling and convection in loft space •
Walls - cavity wall insulation; reduce conduction, convection, radiation (if shiny)
Windows - double glazing; reduce conduction, convection if vacuum or gas at low pressure
Doors - draught excluder; reduce conduction, convection
Floors - carpets; trapped air pockets in wool are good insulators they reduce conduction

18. Home insulation
We can reduce the heat losses from our homes in many ways. Unscramble the list below to find out the ways:
bouled zgnlagi
vytiac llaw sunatoinil
Drghaut xluecder
fotl sunatoinil
arcetps
urctansi
Why do each of these methods work?
Describe which method of heat transfer they reduce

19. Describe how energy is lost through the wall from the inside to the outside and how the insulation reduces the different types of energy loss.
! The quality of written communication will be assessed in your answer to this question.
Describe how energy is lost through the wall from the inside to the outside and how the insulation reduces the different types of energy loss.
! The quality of written communication will be assessed in your answer to this question.
6 marker question
Energy losses in the home can be reduced by energy saving measures.
One measure is to have double-glazed windows which reduce the amount of heat lost by conduction. The gap between the two pieces of glass is usually filled with a gas or a vacuum
Describe how energy is lost through the wall from the inside to the outside and how the insulation reduces the different types of energy loss.
! The quality of written communication will be assessed in your answer to this question

21. Payback and Efficiency
Payback time is the time it takes for an insulation to pay for itself
Payback time = Cost of improvement
saving per year
Efficiency = useful energy out
total energy in e
output
input

22. Payback and Efficiency questions
Dan spends £120 on loft insulation. He is told that this will reduce his bill by £40 per year. Calculate the payback time.
What is payback time?
2. Dan heats his house with coal fires. He is told that his fires are 32% efficient. Explain what this means.
A kettle gives out 80J of heat to the room, and is supplied with 180 J of energy. How efficient is the kettle?
120/40 = 30 years
How long it will take the cost of the item to start saving on energy bills .Its the cost of insulation divided by annual saving.
3. How much useful energy is supplied from a device
= useful = 100J
100/180 = 1.56 J

23. Plenary - To Do Make flash cards for: Heat and temperature
Specific heat capacity and Specific latent heat
Heat transfer (conduction, convection and radiation)
Reducing energy losses from the home
Payback and efficiency
Now use them to test a partner