Chapter 2.4, Problem 36LC

a)

Interpretation Introduction

Interpretation: The boiling of water should be classified as a physical or chemical change.

Concept Introduction: A change that affects the chemical composition of a substance is said to be a chemical change whereas a change that affects the form of a substance but not its chemical composition is said to be a physical change.

Answer to Problem 36LC

Physical change.

Explanation of Solution

During the boiling of water, the change in phase takes place, water changes its phase from liquid to a gaseous state. In this process, there is no change in the chemical composition of water and thus, it is a physical change.

b)

Interpretation Introduction

Interpretation: The salt dissolved in water should be classified as physical or chemical change.

Concept Introduction: A change that affects the chemical composition of a substance is said to be a chemical change whereas a change that affects the form of a substance but not its chemical composition is said to be a physical change.

Answer to Problem 36LC

Chemical change.

Explanation of Solution

When salt is dissolved in water it results in the dissociation of salt into its constituent ions. In this process, there is a change in the chemical composition of salt and thus, it is a chemical change.

c)

Interpretation Introduction

Interpretation: The turning of milk into sour should be classified as a physical or chemical change.

Concept Introduction: A change that affects the chemical composition of a substance is said to be a chemical change whereas a change that affects the form of a substance but not its chemical composition is said to be physical.

Answer to Problem 36LC

Chemical change.

Explanation of Solution

The turning of milk into sour results in the formation of lactic acid from lactose, a sugar found in milk. In this process, there is a change in the chemical composition of milk and thus, it is a chemical change.

d)

Interpretation Introduction

Interpretation: The rusting of metal should be classified as physical or chemical change.

Concept Introduction: A change that affects the chemical composition of a substance is said to be a chemical change whereas a change that affects the form of a substance but not its chemical composition is said to be a physical change.

Answer to Problem 36LC

Chemical change.

Explanation of Solution

During rusting of iron, the iron and oxygen molecules react to make a new compound, iron oxide. In this process, there is a change in the chemical composition of iron and thus, it is a chemical change.