A steam engine converts 150 kg of water completely to steam. The process involves transfer of 4 x 108 J as heat. If steam escaping through the safety valve does 2 x 108 J of work against outside atmosphere, the net change in the internal energy is:

Question

anonymous · Answer

@radar 
@tkhunny

farcher · Answer

The mass of the steam is not needed and this question requires the application of the first law of thermodynamics:

Change in internal energy of a system = heat input to system - work done by system