Chapter 10, Problem 14A

(a)

Interpretation Introduction

Interpretation: Whether burning a match is exothermic or endothermic needs to be explained.

Concept Introduction: In an exothermic reaction energy discharges from the system while in endothermic reaction consumed energy from the surrounding. Chemical energy is the type of potential energy that stores energy in chemical bonds. Chemical energy is consumed when those bonds are created, and chemical energy is discharge when they split.

Answer to Problem 14A

Burning a match is exothermic.

Explanation of Solution

Burning of match is an exothermic reaction as it discharges heat during the burning. On striking the match on match box, the friction produces greater heat energy than the surrounding molecules can take in.

(b)

Interpretation Introduction

Interpretation: Whether water boiling in a kettle is exothermic or endothermic needs to be explained.

Concept Introduction: In an exothermic reaction energy discharges from the system while in endothermic reaction consumed energy from the surrounding. Chemical energy is the type of potential energy that stores energy in chemical bonds. Chemical energy is consumed when those bonds are created, and chemical energy is discharge when they split.

Answer to Problem 14A

Water boiling in a kettle is endothermic process.

Explanation of Solution

In boiling, water absorbs heat so, it is an endothermic process. Once all the intermolecular bonds are broken, the water transforms to steam (water vapor) absolutely. This kind of physical process is called phase change.

(c)

Interpretation Introduction

Interpretation: Whether water freezing is exothermic or endothermic needs to be explained.

Concept Introduction: In an exothermic reaction energy discharges from the system while in endothermic reaction consumed energy from the surrounding. Chemical energy is the type of potential energy that stores energy in chemical bonds. Chemical energy is consumed when those bonds are created, and chemical energy is discharge when they split.

Answer to Problem 14A

Water freezing is exothermic.

Explanation of Solution

Water freezing is an exothermic reaction as it discharges heat during the process. If the water is put in a freezer the water can gradually lose heat to the cold air around it. After losing energy, the water molecules start to move gradually, come closer and pack close enough to turn to ice. The water converts heat into the surrounding area in this process

(d)

Interpretation Introduction

Interpretation: Whether water vapor condensing on a cold pipe exothermic or endothermic needs to be explained.

Concept Introduction: In an exothermic reaction energy discharges from the system while in endothermic reaction consumed energy from the surrounding. Chemical energy is the type of potential energy that stores energy in chemical bonds. Chemical energy is consumed when those bonds are created, and chemical energy is discharge when they split.

Answer to Problem 14A

Water vapor condensing on a cold pipe is exothermic.

Explanation of Solution

Water vapor condensing on a cold pipe an exothermic reaction as it discharges heat during the process. Water vapor discharge energy into the pipe and cools to the point that the vapor molecules transform into a liquid state.

(e)

Interpretation Introduction

Interpretation: Whether warm pack giving off heat is exothermic or endothermic needs to be explained.

Concept Introduction: In an exothermic reaction energy discharges from the system while in endothermic reaction consumed energy from the surrounding. Chemical energy is the type of potential energy that stores energy in chemical bonds. Chemical energy is consumed when those bonds are created, and chemical energy is discharge when they split.

Answer to Problem 14A

Warm pack giving off heat is exothermic.

Explanation of Solution

Warm pack giving off heat an exothermic reaction as it discharges heat during the process. It releases heat from system into surrounding.