Heat transfer

Question 1

How can heat be transferred?

Answer 1

• convection
  -conduction
• radiation

Question 2

What is conduction?

Answer 2

The flow of heat through a material without the flow of the material.

Question 3

What are good conductors and why?

Answer 3

metals - feel cold when you touch it because the heat is quickle conducted away from your hand

Question 4

What are poor conductors called? give an example

Answer 4

Insulators
polystyrene tiles- when you touch it its warm because it stops your hand from losing heat/thermal energy
liquids and gases are also poor conductors

Question 5

Give an experiment to prove that liquids are poor conductors of heat

Answer 5

In a tube there is water and ice seperated by a wire gauze. When heated the water boils and turn into steam while the ice at the bottom doesnt melt.

Question 6

What is convection?

Answer 6

The movement of fluids due to the difference in temperatures that causes hot fluids to flow upwards and cold fluids to flow down.

Question 7

Examples of convection

Answer 7

During the day, the radiation from the sun heats the land more than the sea. The land gets warmer due to conduction, becomes less dense and rises. It is then replaced by the cool sea air. This causes a convection current which results in onshore cool breeze from the sea
- At night this is the opposite. The land is cooler than the sea. The warm air from the sea denses and rises and is replaced by the cool air from the land.

Question 8

What is the convection current?

Answer 8

the cyclic movement of the fluid.

Question 8

Explain convection in the home.

Answer 8

The convector heater releases warm air immediatley above it.
The air rises and travels accross the room. It gets cooler as it falls on the ground to be reheated again

Question 9

What is radiation?

Answer 9

The transfer of heat from one place to another in the form of electromagnetic waves.

Question 10

The energy from the sun is transferred to us in the form of?

Answer 10

Electromagnetic radiation
These waves can travel through the vacuum of space

Question 11

Explain what happens when bodies are hotter/colder than their environment (emitters and absorbers)

Answer 11

• Bodies that are hotter than their environment are net emitters because they emit more radiant energy than they absorb
• bodies that are colder than their environment are net absorbers because they absorb more radiant energy than they emit.

Question 12

What is the relationship between absorbers and emitters?

Answer 12

Good absorbers are poor emitters
Poor emitters are good absorbers

Question 13

Factors affecting the absorption and emission of radiation

Answer 13

• the texture of the surface
• the area of the surface
• the color of the surface

Question 14

Describe the surface of a good conductor and emitter

Answer 14

Dull
Black
Matt
Rough

Question 15

Decribe the surface of a poor absorber and emitter

Answer 15

Shiny
Silver
White
Smooth
Polished

Question 16

Describe an experiment that shows that black is a better emitter

Answer 16

Two detecters are placed at an equal distance from the surface being tested. Both surfaces have a temperature of hot water. When the detector faces the metal it has a higher reading

Question 17

Describe an experiment that shows that black is the better absorbing

Answer 17

An equal amount of radiant energy is placed on a black and white surface. A cork is attached to each plate. The cork falls off the plate with a black inner surface first. The wax quickly gets hot and starts to melt.