P1 1 Transfer Of Energy

Question 0

Can all objects emit infrared radiation?

Answer 0

Yes all objects can emit infrared radiation.

Also, the hotter an object is, the more infrared radiation it emits in a given time.

Question 1

What is infrared radiation?

Answer 1

Infrared radiation is energy transfer by electromagnetic waves.

Question 2

Which surfaces are the best emitters of radiation?

Answer 2

• Dark, mart surfaces emit more infrared radiation than light, shiny surfaces

Question 3

Which surfaces are the best absorbers and reflectors of radiation?

Answer 3

• Dark, matt surfaces absorb more infrared radiation than light shiny surfaces
• Light, shiny surfaces reflect more infrared radiation than dark matt surfaces

Question 4

Name some properties which are used to describe states of matter:

Answer 4

• Flow
• Shape
• Volume
• Density

Question 5

Describe the properties of a solid:

Answer 5

A solid:
• Can't flow
• Fixed shape
• Fixed volume
• Much higher density than a gas

Question 6

Describe the properties of a liquid:

Answer 6

A liquid:
• Can flow
• Fits a container shape
• Has a fixed volume
• Much higher density than a gas

Question 7

Describe the properties of a gas:

Answer 7

A gas:
• Can flow
• Fills container
• Its volume can be changed
• Has a low density compared with a solid or liquid

Question 8

The kinetic theory of matter:

Answer 8

SOLIDS
• The particles in a solid are held to each other in fixed positions
• They vibrate about their fixed positions

LIQUIDS
• The particles in a liquid are in contact with each other
• They move about at random

GASES
• The particles in a gas move about randomly and are much further apart than particles in a solid or liquid

• The particles in a gas have more energy than those in a liquid, which have more energy than those in a solid.

Question 9

Conduction in metals:

Answer 9

• Metals contain lots of free electrons. These electrons move about at random inside the metal and hold the positive metal ions together
• When a metal rod is heated at one end, the free electrons at the hot end gain kinetic energy and diffuse across the metal
• As a result, they transfer energy to the surrounding electrons and ions

Question 10

What is convection?

Answer 10

Convection is the circulation of a fluid (liquid or gas).

Question 11

How does convection work?

Answer 11

The circulation currents are caused because fluids rise when they are heated. So they become less dense. Then, they fall as they could down as cooling makes them more dense. Convection currents transfer energy from the hotter parts to the cooler parts.

Question 12

Uses of convection:

Answer 12

• Hot water at home
• Sea breezes
• Lava lamps

Question 13

What is evaporation?

Answer 13

Evaporation is when a liquid turns into a gas.

Question 14

What is condensation?

Answer 14

Condensation is when a gas turns into a liquid.

Question 15

How does the ‘cooling effect’ work in evaporation?

Answer 15

• Weak attractive forces exist between the molecules in the liquid
• The faster molecules which have more kinetic energy break away from the attraction of the other molecules and leave the liquid
• After they leave, the liquid is cooler as the average kinetic energy of the remaining molecules in the liquid has decreased

Question 16

How to increase the rate of evaporation:

Answer 16

• Increase the surface area of the liquid
• Increase the temperature of the liquid
• Create a draught of air across the liquid’s surface

Question 17

The process of condensation:

Answer 17

• The air in a room is moist or ‘humid’

* A glass pane is a cold surface so water vapour will hit the mirror and cool down

Question 18

How to increase the rate of condensation:

Answer 18

• Increase the surface area

* Reduce the temperature of the surface

Question 19

What does the rate of energy transferred to or from an object depend on?

Answer 19

• The shape, size, and type of material of the object
• The materials the object is in contact with
• The temperature difference between the difference between the object and its surroundings

Question 20

What does the temperature rise of an object depend on?

Answer 20

• The amount of energy supplied to it
• The mass of the substance
• What the substance is

Question 21

What is the specific heat capacity of an object?

Answer 21

The specific heat capacity of a substance is the energy needed or energy transferred to 1 kg of the substance to raise its temperature by 1 degree C.

Question 22

Change of temperature equation:

Answer 22

E = m x c x θ

E = energy transferred in J
c = specific heat capacity J/kg/degrees C
m = mass in kg
θ = temperature change in degrees C

Question 23

Energy transfer from our homes can be reduced by fitting:

Answer 23

• Loft insulation
• Cavity wall insulation
• Double glazing
• Draught proofing
• Aluminium foil behind radiators

Question 24

What do U-values tell us?

Answer 24

U-values tell us how much energy per second passes through different materials.

The lower the U-value, the more effective the material is as an insulator.

Question 25

What is the payback time?

Answer 25

The payback time is the time taken to recover the up-front costs from the savings on fuel bills.