Question

Complete each of the statements below.

When work is done on a system by its surroundings, the sign of w is                           [ Select ]                       ["positive", "negative"]         .

When work is done by a system on its surroundings, the sign of w is                           [ Select ]                       ["negative", "positive"]         .

When q has a negative sign, we can say that heat is transferred                           [ Select ]                       ["from", "into"]         the system                            [ Select ]                       ["from", "into"]         its surroundings.

If ∆U for a system is 0 and w is negative, then q must be                           [ Select ]                       ["positive", "negative"]         .

Answer 1

(1) From Thermodynamics, we know work done on a system by its surrounding, the sign of w is positive.

(2) We now work done by a system on its surrounding , the sign of w is negative.

(3) we know from first law of thermodynamics,

Heat is transferred into the system q > 0

Heat is transferred out of the system � q < 0

In question q is negative so answer will be ["from", into "] its surrounding.

(4) We know from first law of thermodynamics,

∆U = q+w

From question, ∆U = 0 , W = -ve

Put all information from question in abov relationship

0 = q - w

So q = w

So q must be positive