The change in internal energy (ΔΕ) of a system : -8 kJ
The laws of thermodynamics 1 state that: energy can be changed but cannot be destroyed or created
The equation is:
[tex]\tt \Delta U=Q+W[/tex]
Energy owned by the system is expressed as internal energy (U)
This internal energy can change if it absorbs heat Q (U> 0), or releases heat (U <0). Or the internal energy can change if the system does work or accepts work (W)
The sign rules for heat and work are set as follows:
• The system receives heat, Q +
• The system releases heat, Q -
• The system does work, W -
• the system accepts work, W +
5 kJ of work is done on the system : W = +5 kJ
releases 13 kJ of energy to the surroundings : Q = -13 kJ
[tex]\tt \Delta E=-13+5=-8~kJ[/tex]
