10: First law of thermodynamics

Question 1

Define Internal energy

Answer 1

Internal energy of a system is the sum of all random distribution of microscopic KE and microscopic PE of all particles in a substance.

Question 2

Define specific heat capacity

Answer 2

SHC of a substance is the thermal energy per unit mass to raise the temperature of the substance by 1 degree kelvin

Question 3

Define specific latent heat of fusion

Answer 3

SLHF is the amount energy per unit mass required to change the substance from solid to liquid phase at constant temperature

Question 4

Define specific latent heat of vaporisation

Answer 4

SLOV is the amount of energy per unit mass required to change the substance from liquid to gaseous state at constant temperature

Question 5

Define first law of thermodynamics

Answer 5

First law of thermodynamics states that the increase in internal energy is equal to the sum of thermal energy supplied to the system and the work done on the system.

Question 6

State what is:
1.Isothermal
2. Isovolumetric
3. Isobaric
4. Adiabatic
5. Cyclic

Answer 6

1. Temperature constant
2. Volume constant
   3.Pressure constant
3. No heat transfer
4. No net change in Internal energy

Question 7

Imagine graph of (p-v): + state features
1.Isothermal
2. Isovolumetric
3. Isobaric
4. Adiabatic
5. Cyclic

Answer 7

1. curve inwards, shift outwards if temp increase
2. Vertical line, W=0 since ideal gas, if P increase, IE increase and vice versa
3. Horizontal line, if V increase>W decrease, T increase>Q increase, WD = area under graph
4. Similar to 1, however points move from on curve to another; Q=0 since no transfer of heat IE increase = WD
5. Magnitude of net work done is the area bounded, negative or positive determined by context/direction