Question

1. A gas expands and does p-v work on the surroundings equal to

Answer 1

The change in energy of the system : -63 J

Further explanation

Given

279 J work

216 J heat

Required

The change in energy

Solution

Laws of thermodynamics 1

ΔU=Q+W

Rules :

• receives heat, Q +  
• releases heat, Q -  
• work is done by a system, W -  
• work is done on a system, W +  

a gas work on the surrounding : W =-279 J

a gas absorb heat from surrounding : Q = +216 J

Internal energy :

= -279+216

= -63 J