-25 J is the change in internal energy, for a system that does 70 joules of work as it absorbs 45 joules of heat.
According to first law of thermodynamics energy cannot be created or destroyed but it can be changed from one form to another. First law of thermodynamics is also known as the law of conservation of energy.
Equation of first law of thermodynamics
ΔU = Q - W
where,
ΔU = Change in internal energy
Q = Heat added to the system
W = Work done by the system
Now put the values in above equation
ΔU = Q - W
= 45 - 70
= -25 J
Thus from the above conclusion we can say that -25 J is the change in internal energy, for a system that does 70 joules of work as it absorbs 45 joules of heat.
Learn more about the First law of thermodynamics here: https://brainly.com/question/1613201
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