Question

You break a pencil lead. Which statement is true?

A physical change has occurred, with no energy change.

A physical change has occurred, with energy being given off.

A chemical change has occurred, with energy being absorbed.

A chemical change has occurred, with energy being given off.

Answer 1

A physical change has occurred because the chemical make up has not been changed so the correct answer is A.

Answer 2

Answer: Option (A) is the correct answer.

Step-by-step explanation:

A change that causes no difference in chemical composition of a substance is known as a physical change.

For example, breaking a pencil lead is a physical change because it divides the lead into two halves that is, no change in its chemical composition has occurred.

Whereas a change that brings difference in chemical composition of a substance is known as a chemical change.

For example,
`C + 2H_(2) \rightarrow CH_(4)`

Here, chemical composition of both carbon and hydrogen has changes as they chemically reacted together that leads to the formation of methane.

Thus, we can conclude that the statement a physical change has occurred, with no energy change, is true.