Conduction, Convection & IR Radiation

Question 1

a) Conduction mainly happens in: solids, liquids or gases
b) Convection happens only in: liquids and gases, solids and gases, liquids and solids
c) Radiation happens in: gases, solids, all objects

Answer 1

a) solids
b) liquids and gases
c) all objects

Question 2

What is conduction?

Answer 2

Conduction is the transfer of thermal energy through collisions between vibrating particles.

Question 3

Are solids, liquids or gases the best conductors and why?

Answer 3

The closer the particles the better the conductor. Hence, solids are the best conductors as the particles are packed the closest together out of the three states of matter.

Question 4

What makes metals the best conductor out of all solids?

Answer 4

They have free delocalised electrons which can easily collide with particles.

Question 5

What is convection?

Answer 5

Convection is the transfer of thermal energy through the movement of a heated fluid i.e liquids and gases.

Question 6

How does a convection current form?

Answer 6

1. The water near the heat source warms up. The particles gain thermal energy and begin to move around more, gaining kinetic energy.
2. This causes the particles to spread out. The water becomes less dense than the surrounding colder water so the warm water rises.
3. The warm water loses energy to the surroundings and cools down. The particles get closer together and the water becomes more dense.
4. The cooler water sinks and is drawn in to replace the warm water that has risen. This creates a convection current and the process repeats again

Question 7

What is infra-red (IR) radiation?

Answer 7

Infra-red radiation is the transfer of thermal energy where energy is emitted as invisible electromagnetic waves.

Question 8

True or False? IR radiation needs particles to transfer heat.

Answer 8

False, it does not need particles, so it can even travel through a vacuum

Question 9

All objects emit IR radiation. The ………. the object, the ………. IR radiation it emits

Answer 9

hotter, more

Question 10

a) Black surfaces are the ………. emitters and absorbers of heat radiation. However they are ………. at reflecting IR radiation
b) Shiny surfaces are the ………. reflectors of IR radiation. However they are ………. emitters and absorbers of heat radiation.

Answer 10

a) best, poor
b) best, poor