Page 2 - CBW

Reason (R): For the formation of rust, iron must be exposed to air and water.

7. Assertion (A): The expansion of a metal rim upon heating is a reversible change.
Reason (R): Upon cooling, the metal rim contracts and returns to its original size.
8. Formation of clouds is a result
of water cycle.
Is the formation of clouds a

physical or chemical change?
Explain.

9. Case Study 1: Melting of Ice Cream

You left a bowl of ice cream outside on a hot day. After some time, the
ice cream melted and turned into a liquid. Later, you placed the bowl in
the freezer, and the liquid solidified back into ice cream.

Questions:
a) What type of change occurred when the ice cream melted?
b) Is the melting of ice cream a reversible or irreversible change?
c) What does this example illustrate about the nature of physical
changes?

10.
Case Study 2: Metal Lid on a Jar

Scenario: You had difficulty opening a metal jar lid. To loosen
it, you placed the jar under hot water. After a few minutes,
the lid opened easily.

Questions:
a) What type of change occurred when the lid was heated?
b) Is the expansion of the lid a reversible or irreversible change?
c) What does this example illustrate about the nature of physical changes?

11. You have a glass of water at room temperature. You place
it in the freezer, and after a few hours, the water turns
into ice.
Questions:
1. What type of change occurs when water freezes?
Is it reversible or irreversible? Explain.
2. If the ice is left at room temperature, it will melt
back into water. What does this indicate about
the nature of the change?