4/11.22 Physics Help Please! The change in thermal energy of a gas?

Question

11J of heat are removed from a gas sample while it is being compressed by a piston that does 20J of work.

A) What is the change in the thermal energy of the gas?

E(th)= ???J

B) How does change the temperature of the gas?

Increase or decrease?

Answer 1

♠ initial state of certain amount of gas m was:  

p1*V1=(m/μ)*R*T1;

♣ final state of the same amount of gas m is:  

p2*V2=(m/μ)*R*T2;

A) ΔE= 20 –11 =9 J;

B) ΔE= p2*V2 –p1*V1 =

=(m/μ)*R*(T2 –T1) =9 J > 0,

hence T2 >T1; increase!