P2.4 Energy transfers: particles

Question 1

Name a material that is a good conductor of electricity.

Answer 1

Metals and graphite are good conductors of electricity.

Question 2

What is a conductor?

Answer 2

A conductor is a material that conducts charge or energy well, such as a metal or graphite.

Question 3

What is conduction?

Answer 3

Conduction is a way in which energy is transferred through solids, and to a much lesser extent liquids and gases.

Question 4

How do particles transfer energy in conduction?

Answer 4

In conduction, particles transfer energy by colliding with other particles when they vibrate.

Question 5

When does energy transfer happen until?

Answer 5

Energy transfer happens until the two surfaces are at the same temperature.

Question 6

What is an insulator?

Answer 6

An insulator is a material that does not conduct electricity or transfer energy well.

Question 7

Name an example of an insulator.

Answer 7

An example of an insulator is e.g wood, or many non-metals.

Question 8

Do insulators conduct any sort of energy?

Answer 8

Even though insulators are poor conductors of energy, that does not mean that they do not conduct at all, but that energy is transferred very slowly through them.

Question 9

Why do gases not conduct electricity well?

Answer 9

Gases do not conduct well at all because their particles are much further apart than the particles in a solid.

Question 10

What is convection?

Answer 10

Convection is the transfer of energy by the movements of gases or liquids.

Question 11

What is a convection current?

Answer 11

A convection current is the movement of heated liquids or gases.

Question 12

What is radiation?

Answer 12

Radiation is the transfer of energy as a wave.

Question 13

In terms of particles and convection, explain in detail what happens when you heat soup in a pan.

Answer 13

When you heat soup in a pan it all heats up,not just the layer in contact with the bottom ofthe saucepan. This is what happens:

• The soup that is in contact with the bottom of the pan gets hotter so the particles there move faster
• The particles in the soup move further apart, so the soup becomes less dense
• The hotter soup rises and cooler, denser soup takes its place

Question 14

What do solids transfer energy by?

Answer 14

Solids transfer energy by conduction.

Question 15

What do liquids and gases transfer energy by?

Answer 15

Liquids and gases transfer energy by convection.

Question 16

Give an example of something created by a convection current.

Answer 16

E.g hurricanes and winds are created by convection currents.

Question 17

How is wind created?

Answer 17

Wind is created by convection currents along the shoreline/ coast.

Question 18

Why are metals better conductors than other solids?

Answer 18

Metals are better conductors than most other solids because they have delocalized electrons flowing through them which further helps transfer the energy and heat via the vibrations even more.

Question 19

Why are solids good at conducting?

Answer 19

Solids are good at conducting because their particles are packed very closely together and the particles touch their neighbors, which helps transfer the heat through vibrations.

Question 20

Why can conduction only happen effectively through solids?

Answer 20

Conduction can only effectively happen through solids because their particles are very close together, which helps transfer the heat through vibrations. The particles in a fluid are too far apart to vibrate to transfer the energy.

Question 21

What is a fluid?

Answer 21

A fluid is a gas or a liquid.

Question 22

What is density?

Answer 22

Density is the number of particles in a given volume.

Question 23

What is the equation of density?

Answer 23

Density = Mass / volume

Question 24

Explain in terms of particles why convection happens in liquids and gases but not in solids.

Answer 24

The particles in a gas or in a liquid can move; the particles in a solid
cannot. Convection involves the movement of particles to transfer energy.