Heat Transfers

Question 1

What is heat?

Answer 1

Heat is a type of energy that will flow from a warm area to a colder one.

Question 2

What is temperature?

Answer 2

Temperature is a measure of how hot or cold an object is.

It is determined by the average kinetic energy in the object.

Question 3

How is temperature measured?

Answer 3

Temperature is measured in degrees Celsius.

Freezing point of pure water at sea level is 0 degrees Celsius.
The boiling point of pure water at sea level is 100 degrees Celsius.

Question 4

What is heat measured in?

Answer 4

Heat is measured in Joules

Question 5

How does conduction take place in a non-metal?

Answer 5

As the graphite rod is heated, the carbon atoms near the heat source begin to vibrate.
These vibrations make the adjacent atoms vibrate and so on along the rod.
This is how heat is transferred along a non-metal.

Question 6

What materials are poor conductors? Why? What are they used for?

Answer 6

Materials such as wood, glass paper and wool are classified as poor conductors because they offer very large resistance to the flow of heat current. They are often used as insulators.

Question 7

What materials are good conductors of heat? Give an example of what they are used for and why.

Answer 7

Aluminium, copper and steel are all good conductors of heat because that are all metals. Cooking utensils are made from good conductors of heat as food can be cooked more efficiently and in shorter time.

Question 8

Metals are the best conductors of heat because…

Answer 8

… they contain many free electrons.
The free electrons can move between atoms.
The free electrons carry energy atoms further away from the heat source.

Question 9

How does conduction take place in a metal?

Answer 9

A copper rod is heated, the copper atoms pass energy as in non-metals.
The electrons also gain energy but unlike the atoms they are free to move around. This allows them to spread the heat energy to atoms further away.

Question 10

Good non-metal conductors:

Answer 10

Carbon

Graphite

Question 11

Order of best conductors:

Answer 11

Metals(solid)                -best
Non-metals (solid)
Liquids
Gases
Vacuum                         -worst

Question 12

Which state of matter is the best conductor?

Answer 12

Solids. Liquids and gases are both poor conductors.

Question 13

What happens to the particles in a material when heated?

Answer 13

The motion of the particles increase as the particles become more energetic.

Question 14

What happens to particle if only one end of the material is heated?

Answer 14

The atoms pass on energy when a substance is heated, it’s particles gain internal energy and move more vigorously. The particle bump into nearby particles and make them vibrate more. This passes internal energy through the substance by conduction from the hot end to the cold end.

Question 15

Name 6 types of insulation

Answer 15

Double glazing 
Loft insulation
Draft excluders
Curtains
Cavity wall insulation 
Foil behind radiators

Question 16

How does double glazing insulation work and what does it prevent?

Answer 16

Double glazing adds an extra pane of glass to each window. This means that there is a layer of air vacuum between the 2 panes.
This helps prevent heat loss by conduction.

Question 17

How does loft insulation work and what does it prevent?

Answer 17

Loft insulation is plastic foam containing trapped air.

This acts as an insulator to stop conduction of heat through roof tiles.

Question 18

How does draught insulation work and what does it prevent?

Answer 18

Draught excluders are hairy or sponges strips that are placed under doors to prevent the movement of convection currents

Question 19

How do curtains reduce heat transfer? What form do the prevent?

Answer 19

Curtains reduce heat loss by covering up gaps around windows. This helps to prevent the movement of convection currents.

Question 20

How do cavity wall insulators reduce heat transfer and what do they prevent?

Answer 20

Cavity wall insulation involves placing a layer of plastic foam insulation in between two layers of outside walls. This prevents heat loss by both conduction and convection currents.

Question 21

How does foil behind radiators prevent heat loss and by what method?

Answer 21

Place a shiny sheet of foil behind radiators. This prevents heat radiation reaching the wall and going outside via conduction. Instead it is reflected into the room.

Question 22

Conduction

Answer 22

Objects that have to be touching each other

Question 23

Convection

Answer 23

The particles vibrate and move

Question 24

Radiation

Answer 24

Doesn’t use particles and travels in waves