Thermal Concepts

Question 1

What is Avogadro’s Constant?

Answer 1

6.02 x 10^23

Question 2

What is Brownian Motion?

Answer 2

• Where a larger particle (smoke) collides with smaller particles (air).
• The larger particle a random and jerky motion.
• The smaller particles cannot be seen meaning only the large particle can be observed.

Question 3

What is internal energy?`

Answer 3

• When a car moves it collides with an air molecule.
• The car exerts a force on the air molecule.
• Newton’s third law states that the car must experience an equal and opposite reaction.
• This is internal energy and since the gas molecules have no intermolecular bonds, it is all KE.
• “Sum of energy of the molecules of a body.”

Question 4

The relationship between Temperature and KE?

Answer 4

• Temperature is directly related to the KE of the molecules.
• HOWEVER: KE is not directly related to the temperature in °C.
• 0 K = -273 °C

Question 5

Describe conduction.

Answer 5

• When bodies are in contact with each other.
• Fast-moving molecules lose energy.
• Slow-moving gain energy.

Question 6

Describe convection.

Answer 6

• Hot air pushes cold air away

- In a convection current the hot air rises and then as it cools it will fall. The process is repeated.

Question 7

Describe radiation.

Answer 7

• Can pass through a vacuum.

- Infrared

Question 8

What are insulating materials usually made off.

Answer 8

• Fibrous materials that trap pockets of air.

- Air is a poor conductor of heat.

Question 9

What is Thermal Capacity (c)?

Answer 9

• Amount of heat energy needed to raise the temperature of an object by 1 °C
• Unit: J °C^-1 or JK^-1

Question 10

What is Specific Heat Capacity?

Answer 10

• Amount of heat energy required to raise the temperature of 1kg of the material by 1 °C.
• Unit: Jkg^-1 °C^-1.

Question 11

What is the difference between thermal capacity and specific heat capacity.

Answer 11

• Thermal Capacity: Size and what it’s made of.

- Specific Heat Capacity: Only on the material.

Question 12

How can the rate of evaporation be increased?

Answer 12

• Increase Surface Area
• Blowing across the surface
• Raising the temperature

Question 13

What is Specific Latent Heat Capacity?

Answer 13

• Amount of heat required to change the state of 1kg of the material without a change in temperature.
• Unit: Jkg^-1

Question 14

What is the equation for the KE of gas molecules?

Answer 14

• 3/2kT
• Where k = Boltzmann’s constant (1.38 x 10^-23)
• T = Temperature