Consider each of the following processes. would the calculated value of ∆e for the system be a positive or negative answer? a. water warms up when left in the sun (system = water) b. a gas is compressed. (system = the gas) c. a hot object cools when left out. (system = the object) d. in a car engine, a mixture of air and fuel combusts and expands, pushing the piston. (system = the cylinder of the engine)

a. positive

b. positive

c. negative

d. positive

Explanation:

The Entropy (E) of  a system represents the degree of disorderliness of a system. The entropy of a system is directly proportional to the temperature of the system.

As water warms up, the temperature of the water increases and the entropy increases. Hence, change in entropy is positive.

The random movement of molecules in a gas that is compressed increases and forces such as friction generates heat into the system, leading to an increase in entropy.

A hot object that cools down when left out loses heat and this leads to a reduction in entropy and hence, a negative entropy change.

Combustion within an engine generally generates heat and leads to an increased entropy. Hence, combustion leads to a positive change in entropy.