1. a. What is the first law of thermodynamics? b. What is work and what is heat?
ID: 549016 • Letter: 1
Question
1. a. What is the first law of thermodynamics? b. What is work and what is heat? c. How is the internal energy of a system altered? d. For each of the following energy transfers, what would be the change in internal energy? In each case, is the internal energy increasing or decreasing? 1. w =-150 Joules and q = 50 joules 11. w = 150 calories and q =-50 calories. iii. The work performed is -250 J and the heat transferred is 250 J (Selected answers: (d) i: U =-100 J, energy of the system is lowered)Explanation / Answer
Ans (a) first law of thermodynamics states that energy cannot be created nor destroyed , only it can be transferred from one state to another.
(b) heat is a one form of energy and it is represented by q. And work is a energy and represented by w.
(c) internal energy du, is a sum of work done and heat
du = dw + dq
(d) (i) du = -150 + 50 = -100J
(ii) du = 150 cal - 50 cal = + 100 cal
(iii) du = -250 + 250 = 0 J
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