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SCIENCE P1 > Keeping Houses Warm > Flashcards

Flashcards in Keeping Houses Warm Deck (26):
0

What is a conductor

A material that allows heat to spread through quickly eg metals

1

Insulators are...

Materials that allow heat energy to spread through slowly

2

What are convection currents

Movement of hot air rising and cooler air taking its place.
Warm air becomes less dense and rises,the particles move quickly away from each other and expand, being replaced by denser air.

3

How do walls lose energy in the home

They absorb heat radiation

4

Energy is lost from SOURCE to...

SINK

5

Energy efficiency measures what

How good an appliance is at converting input energy into useful output energy

6

What does the amount of infrared given out/taken in depend on

How much infrared given out/taken in depends on ITS SURFACE

Transfer of heat energy by electromagnetic waves

7

How does conduction work

It is the transfer of heat energy through a substance from hotter to cooler without substance moving itself. Kinetic energy increases so particles vibrate. Energy transfers and passes along

8

What is radiation (on hot objects)

Transfer of heat energy by electromagnetic waves

Hot objects emit mainly infrared radiation which can pass through a vacuum so no material is needed for the transfer

10

What surface emits more radiation at room temperature

Dark matt

11

Heat can also move as infrared radiation (electromagnetic wave)

What surface reflects infrared

Shiny surfaces

Wont get as hot

11

Which surface is a better absorber of radiation

Dark matte

12

How does fibreglass loft insulation reduce heat loss in the home

Reduces convection and conduction by trapping layers of air between fibres

13

How do reflective foil on walls behind radiators reduce heat loss in the home

Reduces radiation by reflecting infrared heat energy into the room

14

For a television what is the input energy, useful energy and wasted energy

Electrical energy is input
Sound and light energy is output
Heat energy is wasted

15

How does cavity wall insulation reduce heat loss in the home

Reduces conduction and convection by trapping small pockets of air in the foam

15

How does double glazing reduce heat loss in the home

Reduces conduction and convection by trapping air between panes of glass

15

Amount of radiation given out depends on what (in a material)

How much infrared given out/taken in depends on it's surface

15

Why are metals good conductors

Heat energy is also transferred by free electrons in a metal

They flow, collide with and transfer energy to other atoms increasing their kinetic energy so temperature rises

16

How do draught excluders reduce heat loss in the home

Reduces convection by keeping as much warm air inside as possible

17

What type of heat loss does insulation only prevent

Heat loss by conduction

18

How does convection cause heat loss

Because liquids and gases can easily flow they can transfer heat energy from hotter to cooler regions by their own movement. Cools overall temperature

Fast particles expand and become less dense so rise up to be replaces with denser liquid or gas

19

When heat is lost from a home what is the source and what is the sink

Home is source
Atmosphere is sink

20

Describe particle movement in a hotter object

Fast moving particles

In a solid they vibrate
In a liquid they flow past each other and move further apart

21

Why are refrigerators insulated

To reduce heat gain by conduction or convection

22

Why are curtains good insulators

Trap air between them and window helping to reduce heat energy loss by conduction