Question

Alan wrote the following examples of changes in substance.

Answer 1

Answer:

The correct option is B

Explanation:

A physical change is characterized by the following

• no new substance is formed
• easily reversible
• cannot be represented by a chemical reaction

A chemical change is characterized by the following

• new substances are formed
• easily reversible
• can be represented by a chemical reaction

A camp fire is usually made by burning woods. This process is called combustion, it involves the burning of a substance in oxygen to produce carbon dioxide (CO₂). This is a chemical change because new substance (CO₂) is formed and the ashes formed (after burning) cannot be reversed back to wood.

Plants convert carbon dioxide and water into glucose and oxygen through photosynthesis. This process is also a chemical change because new substances (glucose and oxygen) are formed and the reaction cannot also be easily reversed.

The reaction involved can be represented as  

6CO₂ + 6H₂O ⇒ C₆H₁₂O₆ + 6O₂

Answer 2

A campfire being lighted and plants converting carbon-dioxide and water into glucose and oxygen are both forms of chemical change.

Therefore, the answer is:

B. Both are examples of chemical change.