Ideal Gases + Thermodynamics

Question 1

Ideal Gas

Answer 1

A gas which obeys the equation pV = nRT at all pressures, volumes, and temperatures.

Question 2

Absolute zero (0K)

Answer 2

The zero point of the thermodynamic temperature scale and the temperature at which all substances have a minimum internal energy

Question 3

Thermal equilibrium

Answer 3

When there is no net flow of heat between two objects in thermal contact, the two objects are in a state of thermal equilibrium

Question 4

Absolute scale of temperature

Answer 4

It is the scale that is independent of the property of any substance and has an absolute zero

Question 5

First Law of thermodynamics

Answer 5

The first law of thermodynamics states that the increase in the internal energy of a system is equal to the sum of the heat supplied to the system and the work done on the system, and the internal energy of a system depends only on its state.

Question 6

Internal energy

Answer 6

The internal energy of a system is the sum of microscopic KE, due to random motion of particles, and microscopic PE, associated with the intermolecular forces of the system.

Question 7

Heat Capacity

Answer 7

The quantity of heat required to cause a unit rise in temperature of a body

Question 8

Specific Heat Capacity

Answer 8

The quantity of heat required per unit mass to cause a unit rise in temperature of a body

Question 9

Cyclic Process

Answer 9

A process in which the system goes through a series of processes and ends at its initial state

Question 10

Specific Latent heat of fusion

Answer 10

The quantity of heat required to convert unit mass of solid to liquid without any change in temperature

Question 11

Specific Latent heat of vaporisation

Answer 11

The quantity of heat required to convert unit mass of liquid to gas without any change of temperature

Question 12

Where does microscopic KE come from

Answer 12

The microscopic KE arises due to the kinetic energies of the particles due to their constant random motion, which can be rotational, translational and vibrational

Question 13

Where does microscopic PE come from

Answer 13

The microscopic PE of a body arises due to the potential energies of the particles, arising from the interactions between them

Question 14

KE as a result of random motion of gas molecules in a system

+

Mean KE <KE></KE>

Answer 14

3/2nRT = 3/2pV = 3/2NkT

3/2kT = Total KE/N (number of molecules)

Question 15

Work done by gas in p - V graph

Answer 15

area under curve; make sure to take note of any possibly missing squares (ie they don’t include the 0 points of both axis)

Question 16

Isotherm

Answer 16

Defn: The change in volume and pressure of the gas occurs without a change in temperature

No change in Temperature
Delta U = 0
Q = -W

Question 17

Isobar

Answer 17

Defn: The gas undergoes heat exchange such that its volume change occurs under constant pressure

No change in Pressure
Rightward Shift -> W < 0
Leftward Shift -> W > 0

Question 18

Isovolumetric/ Isochoric/Isometric

Answer 18

Defn: a Change in pressure of the gas occurs without a change in volume

No change in Volume
W = 0
Delta U = Q

Question 19

Adiabatic

Answer 19

Defn: The change in pressure and volume of the system occurs without any heat transfer into and out of the system

Look out for ‘Insulated’ or ‘process happens quickly’
No transfer of Heat
Q = 0
Delta U = W

Question 20

Pressure

Answer 20

(nRT)/V = 1/3(density, rho)(squared Vrms, <v^2>)

Question 21

Internal energy of an Ideal Gas

Answer 21

The sum of microscopic kinetic energies of the molecules due to their random motion.

Ideal gases have no PE due to lack of interactions between particles aside from collisions