Chapter 18, Problem 102A

Solution

(a)

Interpretation: A campfire "fanned" to help get it going is to be explained.

Concept Introduction: Oxygen is not combustible but can accelerate and facilitate the combustion of other substances.

A campfire "fanned" to help get it going is a spontaneous process.

When a campfire is "fanned" and supplied with more oxygen, the campfire is ignited and burns more quickly and with more flames. This process results in an increase in entropy due to a temperature increase. Since the entropy increase hence the process is spontaneous.

(b)

Interpretation: Ice cubes melt faster than a block of ice with the same mass is to be explained.

Concept Introduction: Entropy may be described as a system's degree of disorder.

Ice cubes melt faster than a block of ice with the same mass because it is a spontaneous process.

The melting of ice cubes occurs more quickly than the block of ice with the same mass because the melting of ice cubes has a higher entropy than the block of ice. This means that melting ice cubes is a process that is favored and more spontaneous.

(c)

Interpretation: Manganese dioxide not changed when hydrogen peroxide exposed by adding a pinch of powdered manganese dioxide is to be explained.

Concept Introduction: A catalyst is a substance that speeds up a chemical process without any chemical change.

Manganese dioxide does not change during the chemical reaction because it is a catalyst.

Manganese dioxide does not change when hydrogen peroxide is exposed by adding a pinch of powdered manganese dioxide because manganese dioxide is a catalyst. Catalysts do not change during the reaction.