Thermodynamics

Question 1

Define Heat

Answer 1

The transfer of energy from one object to another.

Question 2

Define Temperature

Answer 2

Measurement of how much heat is present in an object.

Question 3

What is absolute zero?

Answer 3

Molecules will not be moving, therefore have no kinetic energy. 0°C = 273.15K

Question 4

Kinetic Theory

Answer 4

Consideration of the microscopic movement of particles will predict the macroscopic behaviour of a substance.

Question 5

What is potential energy?

Answer 5

PE is due to the binding energy in bonds between molecules.

Question 6

Define internal energy.

Answer 6

The sum of the kinetic and potential energies of all the molecules within a given mass of a substance.

Question 7

What does Maxwell-Boltzmann distribution show?

Answer 7

There are no molecules with zero energy.
There are only a few molecules with high energy.
There is no maximum value for the energy a molecule can have.

Question 8

What happens Maxwell-Boltzmann distribution if temp increases?

Answer 8

The peak on the graph moves towards higher energies - higher speeds.

Question 9

Zeroth Law of Thermodynamics.

Answer 9

Objects in thermal contact are at the same temperature.

Question 10

First Law of Thermodynamics.

Answer 10

Energy is conserved. Change in internal energy = heat transferred + work done.
μ = Q + W

Question 11

How do you calculate the root mean square.

Answer 11

rms = the sum of the square of individual speed of molecules divided by number of molecules, then taking the square root of that mean.

Question 12

Average molecular ke

Answer 12

average ke is proportional to the absolute temp of the gas

1/2m = 3/2kT

Question 13

Define Specific Heat Capacity.

Answer 13

The amount of energy required to raise the temperature of 1kg of substance by 1 Kelvin.
ΔE = mcΔθ

Question 14

Define Specific Latent Heat

Answer 14

The energy required to change the state of a substance of 1kg at a constant temperature.
ΔE = LΔm

Question 15

Black Body Radiator

Answer 15

Theoretical object, that absorbs and emits EM radiation at all wavelengths.

Question 16

Boyles Law

Answer 16

For constant mass, at a constant temp, pressure is inversely proportional to volume.

Question 17

Charles Law

Answer 17

For constant mass, at constant pressure, volume is proportional to absolute temperature.

Question 18

Gay Lussacs/ Pressure Law

Answer 18

For constant mass, at const volume, pressure is proportional to absolute temperature.

Question 19

Ideal Gas Assumptions

Answer 19

• Molecules have negligible size and are identical.
• Collisions are perfectly elastic.
• Molecules exert no forces on each other, except during collisions - no PE
• Motion is random

Question 20

Ideal Gas Equation

Answer 20

pV = NkT - N is number of molecules
pV = nRT - n is number of moles. R = 8.31 Jmol^-1kg^-1

Question 21

Explain why the internal energy of an ideal gas is only kinetic.

Answer 21

as ideal gases do not have forces between molecules so no potential energy

Question 22

Describe how the concept of an absolute zero of temperature arises from ideal gas laws

Answer 22

pV = nRT. At absolute zero, pV = zero

Question 23

Describe how the concept of an absolute zero of temperature arises the kinetic model of an ideal gas

Answer 23

at absolute zero the molecules have

no kinetic energy, so molecules stationary

Question 24

The article also states that the internal energy of the air in the balloon could become
zero if the temperature of the gas became low enough.
Explain what is meant by the internal energy of the air and discuss whether the
statement is correct.

Answer 24

Internal energy is the sum of the potential and kinetic energies. In an ideal gas the molecules only have kinetic energy. KE=3/2kT. Above 0K air molecules are in continual random motion. If gas reached absolute zero, KE of molecules would be zero so statement correct. If not ideal gas, molecules would have potential energy at 0K, so statement incorrect.