Thermal Physics

Question 1

What is heat ?

Answer 1

Heat is a form of energy measured in joules (relates to the average Ek of the molecules within a system )

Question 2

What is temperature?

Answer 2

A measure of how hot something is measured in kelvins or Celsius (a measure of the average kinetic energy of particles within a substance)

Question 3

What is thermal equilibrium?

Answer 3

When two or more bodies have the same temperature and no net flow of energy between the bodies

Question 4

What happens if there are two objects (one hotter than the other ) ?

Answer 4

As energy flows from higher temperatures to lower temperatures via molecular collisions which impart Ek into other particles .

This results in the Ek of all particles to be the same meaning both objects have the same temperature therefore there wouldn’t be any net flow of energy

Question 5

What does net flow mean ?

Answer 5

Equal amounts of energy flowing either way

Question 6

Laws of thermodynamics (zeroth ) :

Answer 6

If two systems are in thermal equilibrium with a third system then those two are in equilibrium with each other.

Question 7

What are diathermal walls ?

Answer 7

Walls which allow heat to flow in and out of systems

Question 8

What are adiabatic walls ?

Answer 8

Walls that do not allow heat to flow in and out of the system

Question 9

Why do all particles above absolute zero have internal energy?

Answer 9

All particles within a substance above absolute zero are always vibrating or moving around meaning they have kinetic energy.

As internal energy is the sum of kinetic and potential energy , any substance above absolute zero must have internal energy

Question 10

How can you change the internal energy of an object ?

Answer 10

• transferring heat or energy
• doing work on the object

Question 11

How does providing heat change the internal energy?

Answer 11

When heat is applied there is an increase in the kinetic energy changing the temperature or change the state providing more potential energy

Question 12

How does doing work on the object change the internal energy ?

Answer 12

Doing work results in the volume of the object to be changed resulting in the object to expand or contract changing the potential energy

Question 13

What is specific heat capacity?

Answer 13

It is the energy required to change the temperature of a kilogram of a substance by 1k (1 degree )

Question 14

What is the equation for specific heat capacity?

Answer 14

Q= MC(change in temperature)

Question 15

What is the unit for specific heat capacity?

Answer 15

Jkg^-1 k^-1

Question 16

When energy is lost by the hotter object what would the change in temperature be ? (Two substances reaching thermal equilibrium)

Answer 16

Initial temperature - final temperature

Question 17

When the energy is gained by the cooler object what is the change in temperature? (Two substances in thermal equilibrium)

Answer 17

Final temperature- initial temperature

Question 18

Why is energy gained by the cooler temperature?

Answer 18

Heat energy flows from a substance with a higher temperature to a lower temperature

Question 19

What does the Maxwell-Boltzmann distribution show us ?

Answer 19

It shows us how the kinetic energy is spread within the molecules of a substance

Question 20

If a substance had a low specific heat capacity. How fast would it heat and cool ?

Answer 20

Quickly

Question 21

If a substance had a high specific heat capacity. How fast would it heat and cool ?

Answer 21

Slowly