Thermal Physics

Question 1

What is absolute zero?

Answer 1

The lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy

Question 2

What is avogadro’s constant?

Answer 2

The number of particles that make up one mole of any gas
6.022 x 10^23

Question 3

What is Boltzmann’s constant (k)?

Answer 3

A constant relating the average kinetic energy of the particles in a gas, to the gas’ temperature

Question 4

What is Boyle’s law?

Answer 4

The pressure of an ideal gas is inversely proportional to its volume when held at constant temperature

Question 5

What is Brownian motion?

Answer 5

The seemingly random motion of particles

Question 6

What is Charles’ law?

Answer 6

The volume of an ideal gas is directly proportional to its absolute temperature when held at constant pressure

Question 7

What is an ideal gas?

Answer 7

A gas that meets the ideal gas assumptions. All the gas laws are based on ideal gases

Question 8

What is internal energy?

Answer 8

The sum of the randomly distributed kinetic and potential energies of all the particles in a given system

Question 9

What is the Kelvin scale?

Answer 9

An absolute temperature scale that starts at absolute zero (0K = -273C)

Question 10

What is the molar gas constant?

Answer 10

A fundamental constant, used in the ideal gas law

Question 11

What is molar mass (M)?

Answer 11

The mass of one mole of the substance in question

Question 12

What is molecular mass?

Answer 12

The mass of one molecule of the substance in question

Question 13

What is the pressure law?

Answer 13

The pressure of an ideal gas is directly proportional to its absolute temperature, when the volume is fixed

Question 14

What is the specific heat capacity?

Answer 14

The amount of energy required to increase the temperature of 1kg of a substance by 1 Kelvin

Question 15

What is the specific latent heat?

Answer 15

The amount of energy required to change the state of 1kg of a substance without a change of temperature

Question 16

What are the ideal gas assumptions?

Answer 16

• large number of molecules in random, rapid motion
• particles occupy negligible volume compared to the volume of gas
• all collisions are perfectly elastic and the time of the collisions is negligible compared to the time between collisions
• negligible forces between particles except during collision

Question 17

How does the ideal gas model explain the presence of gas pressure?

Answer 17

• pressure = force/area
• force = change in momentum/time
• the particle collides with the container wall, changing the momentum
• the change in momentum = mv - -mv
∴ change in momentum = 2mv
So, force on the particle from the wall = 2mv/t
By N3, there is a force on the wall from the particle which also = 2mv/t
∴ Pressure on wall = (2mv/t)/A x N

Question 18

State the equation for specific heat capacity

Answer 18

Q = mcΔθ

Q - thermal energy
m - mass
c - specific heat capacity
Δθ - change in temperature

Question 19

Define specific latent heat of fusion

Answer 19

The specific latent heat of fusion is defined as the thermal energy required to convert 1kg of solid to liquid with no change in temperature

Question 20

Define specific latent heat of vaporisation

Answer 20

The specific latent heat of vaporisation is defined as the thermal energy required to convert 1kg of liquid to gas with no change in temperature

Question 21

State the equation for specific latent heat

Answer 21

Q = mL

Q - thermal energy
m - mass
L - specific latent heat

Question 22

State the equation linking mass (m), molar mass (M), and number of moles (n)

Answer 22

Mass = molar mass x number of moles
m = Mn

Question 23

State the equation linking number of atoms (N), number of moles (n), and Avogadro’s constant (Na)

Answer 23

Number of atoms = number of moles x Avogadro’s constant
N = nNa