Question

A steam engine receives 300 kJ of heat from its environment and does 400 kJ of work. How much does the energy of the steam engine change?

Answer 1

Energy of system is decreased by `"100 kilojoules"`

Explanation:

Form 1st law of thermodynamics

`"dU = dQ + dW"`

`"dU = 300 kJ + (-400 kJ)"`

[Work is done by the steam engine. Hence i took -400 kJ]

`"dU = -100 kJ"`