Thermal processes

Question 1

Define thermal equilibrium

Answer 1

Thermal equilibrium is a state in which 2 or more objects have the same temperature and there is no net energy transfer between them

Question 2

Describe conduction in terms of particles

Answer 2

• Particles at hotter end gain kinetic energy and vibrate more vigorously
• Hotter particles collide with neighbouring particles, transferring kinetic energy from one particle to another
  (Metals have free electrons that move to cooler regions and transfer kinetic energy upon collisions with other particles)

Question 3

Define conduction

Answer 3

Conduction is the transfer of heat through a medium without the physical movement of the medium

Question 4

Which states does convection occur in

Answer 4

Liquids and gases

Question 5

Define convection

Answer 5

Convection is the transfer of heat from one place to another by the physical movement of a medium

Question 6

Describe heating of a liquid in terms of convection

Answer 6

• Liquid near heat source gains heat, expands, becomes less dense and rises
• Cooler, denser liquid sinks
• Convection current set up which heats up the whole liquid

Question 6

What enables convection to occur

Answer 6

• Convection currents due to difference in density

Question 7

Describe cooling of a room in terms of convection

Answer 7

• Air near air-con loses heat, contracts, becomes denser and sinks
• Warmer, less dense air rises
• Convection current set up which cools to whole room

Question 8

Define radiation

Answer 8

Radiation is the transfer of heat in the form of infrared radiation without the need for a medium

Question 9

What are the factors affecting rate of absorption and emission of radiation

Answer 9

• Colour
• Texture
• Temperature
• Surface area