Thermal Physics 🌡️

Question 1

What is internal energy?

Answer 1

The sum of the randomly distributed kinetic and potential energies of the PARTICLES within a substance.

Question 2

What is the internal energy of an ideal gas?

Answer 2

The sum of the randomly distributed kinetic energies of the atoms within a substance. (ideal gases have no potential energy)

Question 3

What are the assumptions of kinetic theory?

Answer 3

• Particles have rapid and random motion
• Particles don’t exert forces on each other except during collisions
• The duration of a collision is negligible compared to the time spent between collisions
• Volume of a particle is negligible compared to the volume of the gas
• There is a large amount of particles
• All collisions are elastic

Question 4

Define specific latent heat

Answer 4

The energy required per unit mass to change the state of a substance with no change in temperature.

Question 5

State Boyle’s law

Answer 5

For a gas of fixed temperature, pressure is inversely proportional to volume, pV = constant

Question 6

State Charle’s law

Answer 6

For a gas at a constant pressure, volume is directly proportional to temperature, V/T=constant

Question 7

State the pressure law

Answer 7

For a gas of fixed volume, pressure is directly proportional to temperature, p/T=constant

Question 8

Describe how Boyle’s law can be investigated

Answer 8

• pV=constant
• Fill a syringe with gas and connect it to a pressure gauge
• Vary the volume of the gas using the syringe
• Plot p (y) against 1/V (x)
• Move syringe slowly to avoid heating due to friction

Question 9

How do you convert between *C and K?

Answer 9

T = Theta + 273

Question 10

What is brownian motion?

Answer 10

The observed random motion of particles in a gas or liquid due to collisions with the gas or liquid particles -> evidence for the atomic nature of matter

Question 11

Describe the arrangement of particles in a solid

Answer 11

• Strong electrostatic forces
• Regular arrangement
• Particles vibrate about fixed positions
• Negative PE as energy has to be supplied to separate the particles

Question 12

Describe the arrangement of particles in a liquid

Answer 12

• Particles can move past each other
• Particles have negative PE as energy is required to separate the particles

Question 13

Describe the arrangement of particles in a gas

Answer 13

Negligible electrostatic forces between particles

Question 14

How do the vibrations of particles in a solid change as KE/temperature increases

Answer 14

The amplitude of the vibrations increases