Chapter 3, Problem 43A

Interpretation Introduction

Interpretation:

Whether breaking a pencil in two, is a chemical change or physical change should be classified.

Concept introduction:

The nature of any substance is explained by its chemical properties and physical properties.

A physical property describes the physical changes of a substance. Physical change is a temporary change; it is a reversible change. For example, color, mass, volume, etc.

A chemical property describes how a substance reacts with other substances. In a chemical change, a new substance is formed and absorption of energy or loss of energy occurs; it is an irreversible change. For example, rusting, dissolving, etc.

Answer to Problem 43A

Breaking a pencil in two is an example of physical change.

Explanation of Solution

Breaking of a pencil means the breakdown of the same substance into two parts. If in any changes the composition of compounds remains the same then it is categorized in physical change.

The pencil is divided into two parts but the material is the same for both parts and there is no new substance is formed. So, it is considered in physical change.

In a chemical change, the main important point is the formation of a new substance; in the given example, no new substance is formed. So, it is not considered ina chemical change.

Interpretation Introduction

(b)

Interpretation:

Wherher freezing and formation of ice is a chemical change or physical change needs to be determined.

Concept introduction:

The nature of any substance is explained by its chemical properties and physical properties.

A physical property describes the physical changes of a substance. Physical change is a temporary change; it is a reversible change. For example, color, mass, volume, etc.

A chemical property describes how a substance reacts with other substances. In a chemical change, a new substance is formed and absorption of energy or loss of energy occurs; it is an irreversible change. For example, rusting, dissolving, etc.

Answer to Problem 43A

Water freezing and forming ice is a physical change.

Explanation of Solution

If in any changes the composition of compounds remains the same then it is categorized in physical change. The liquid changes into solid when the intermolecular space is decreased and the arrangement of molecules is got fixed and form a complex structure that is ice. So, it considered as physical change.

In a chemical change, the main important point is the formation of a new substance; in the given example, no new substance is formed. So, it is not considered in a chemical change.

Interpretation Introduction

(c)

Interpretation:

Whether frying an egg is a physical or chemical change needs to be determined.

Concept introduction:

The nature of any substance is explained by its chemical properties and physical properties.

A physical property describes the physical changes of a substance. Physical change is a temporary change; it is a reversible change. For example, color, mass, volume, etc.

A chemical property describes how a substance reacts with other substances. In a chemical change, a new substance is formed and absorption of energy or loss of energy occurs; it is an irreversible change. For example, rusting, dissolving, etc.

Answer to Problem 43A

Frying an egg is a chemical change.

Explanation of Solution

In a chemical change, heat will be absorbed and the chemical bond will break.

While frying an egg, the new substance will be formed. So, it is considered a chemical change.

Chemically change is an irreversible process. By applying extra temperature change in the structure of the substance is a chemical change. And in a chemical change absorption of energy or loss of energy occurs in a chemical reaction.

The statement in the given questionis an irreversible process. So, it is not considered physical change.

Interpretation Introduction

(d)

Interpretation:

Whether burning wood is a chemical or physical change needs to be explained.

Concept introduction:

The nature of any substance is explained by its chemical properties and physical properties.

A physical property describes the physical changes of a substance. Physical change is a temporary change; it is a reversible change. For example, color, mass, volume, etc.

A chemical property describes how a substance reacts with other substances. In a chemical change, a new substance is formed and absorption of energy or loss of energy occurs; it is an irreversible change. For example, rusting, dissolving, etc.

Answer to Problem 43A

The burning of wood is an example of chemical change.

Explanation of Solution

Burning is the process wherenew substanceswill be formed in the end. The wood is formed by hydrocarbon and other components. Burning of the wood changes the structure, and form a new substance as ash and also, releases some gas. This change is irreversible. So, it is a chemical change.

The statement in the given question is an irreversible process. So, it is not considered physical change.

Interpretation Introduction

(e)

Interpretation:

Whether leaves changing colors in the fall is a chemical or physical change needs to be determined.

Concept introduction:

The nature of any substance is explained by its chemical properties and physical properties.

A physical property describes the physical changes of a substance. Physical change is a temporary change; it is a reversible change. For example, color, mass, volume, etc.

A chemical property describes how a substance reacts with other substances. In a chemical change, a new substance is formed and absorption of energy or loss of energy occurs; it is an irreversible change. For example, rusting, dissolving, etc.

Answer to Problem 43A

Leaves changing colors in the fall is a chemical change.

Explanation of Solution

Leaves fall with the change in color is the natural process where a new substance will be formed. This is a biochemical change. This means that color changing is a biochemical process. So. It is considered in a chemical change.

The statement in the given question is an irreversible process. So, it is not considered physical change.