Lakhmir Singh and Manjit Kaur Solutions for Chapter: Changes Around Us, Exercise 5: Questions Based on High Order Thinking Skills (HOTS)

When electricity is passed through water, then two gases, hydrogen and oxygen are produced. On the other hand, when heat is supplied to water, then another gas, steam, is produced. What type of change takes place.
(a) in the first case?
(b) in the second case?

A white powdery substance $\mathrm{X}$ immediately sets into a hard mass on adding a liquid $\mathrm{Y}$ to it. In hospitals, a thick coat of the paste of substance $\mathrm{X}$ is applied over the bandage on the fractured bone of a patient to keep the fractured bone in place to get joined properly.
(a) What could the substance $\mathrm{X}$ be?
(b) Name the liquid $\mathrm{Y}$.
(c) What type of change occurs in $\mathrm{X}$ on adding $\mathrm{Y}$?

An iron rim is made slightly smaller than the wooden wheel (around which it is to be fitted). This iron rim is heated uniformly due to which it undergoes a change $\mathrm{P}$ and can be easily put around the wooden wheel. When cold water is poured over this hot iron rim, it undergoes another change $\mathrm{Q}$ and fits tightly over the wooden wheel. After a considerable time, a change $\mathrm{R}$ takes place in the iron rim due to which a red-brown coating is formed on it.
(a) What are the changes (i) $\mathrm{P}$ (ii) $\mathrm{Q}$ and (iii) $\mathrm{R}$?
(b) Out of $\mathrm{P}, \mathrm{Q}$ and $\mathrm{R}$, which change! changes is/are reversible?

When a liquid $\mathrm{X}$ is added to a grey, powdery substance $\mathrm{Y}$, the substance $\mathrm{Y}$ slowly sets into a hard mass. A thick paste of substance $\mathrm{Y}$ and sand made in Liquid $\mathrm{X}$ is used for plastering the walls of houses.

(a) What could the liquid $\mathrm{X}$ be?

(b) Name the substance $\mathrm{Y}$.

(c) What type of change occurs on adding $\mathrm{X}$ to $\mathrm{Y}$?

Name the cause of change which takes place during the conversion of ice into water.

Name the cause of change which takes place during the conversion of water into hydrogen and oxygen. (Electricity / Fire)

Name the cause of change which takes place during the formation of image of a person on a photographic film. (Electricity/ Light)

Name the cause of change which takes place during the bending of iron rods to make an iron grill. (Light / Force)