B3: Gas Laws

Question 1

What does a positive value of W mean

Answer 1

Work is done by the gas in expanding
Volume of gas increases

Question 2

What does a negative value of W mean

Answer 2

Work is done on the gas to contract
Volume of gas decreases

Question 3

What are all the types of processes in thermodynamics

Answer 3

Isothermal (Temp is constant)
Adiabatic (No thermal energy Q is transferred to the gas system)
Isovolumetric (volume V is constant)
Isobaric (Gas pressure P is constant)

Question 4

In an adiabatic process, why does temperature increase when the gas is compressed

Answer 4

In an adiabatic process, Q = 0, so ΔU = -W
When the gas is compressed, work is done, so the value of W is negative. -W will be positive so ΔU will also be positive.
Since ΔU = (3/2nR)ΔT, ΔT will also be positive, thus temperature increases

Question 5

How can work done by calculated graphically

Answer 5

Work done is the area under the P-V curve

Question 6

What is the second law of thermodynamics

Answer 6

Thermal energy can flow spontaneously from a ho to cold object, it will not flow spontaneously from a cold to hot object