While teaching the topic of physical and chemical changes, Mahima’s teacher listed the conditions that take place during a change.
I. Change in state
II. Change in colour
III. Evolution of a gas
IV. Change in temperature
He then asked Mahima to identify the conditions based on which it can be said with certainty that a particular change is chemical in nature.
Among the changes that are listed by the teacher, which changes should be selected by Mahima?
While teaching the topic of physical and chemical changes, Mahima’s teacher listed the conditions that take place during a change.
I. Change in state
II. Change in colour
III. Evolution of a gas
IV. Change in temperature
He then asked Mahima to identify the conditions based on which it can be said with certainty that a particular change is chemical in nature.
Among the changes that are listed by the teacher, which changes should be selected by Mahima?
The correct option is B Only III
Any change that is accompanied by evolution of gas is known as a chemical change. Therefore, whenever a gas is evolved in a process, it can be said with certainty that a chemical change has taken place.
The correct answer is B.
Why alternatives A, C and D are wrong:
Change in state can take place in both physical and chemical changes. For example, Change in colour can also take place in both types of changes. For example, when iron is heated, its colour changes to red and when iron rod is dipped in copper sulphate solution, which is blue in colour, the colour of the solution changes to green because of formation of iron (II) sulphate.
Similarly, change in temperature can also take place in physical as well as chemical changes.
Only III
Any change that is accompanied by evolution of gas is known as a chemical change. Therefore, whenever a gas is evolved in a process, it can be said with certainty that a chemical change has taken place.
The correct answer is B.
Why alternatives A, C and D are wrong:
Change in state can take place in both physical and chemical changes. For example, Change in colour can also take place in both types of changes. For example, when iron is heated, its colour changes to red and when iron rod is dipped in copper sulphate solution, which is blue in colour, the colour of the solution changes to green because of formation of iron (II) sulphate.
Similarly, change in temperature can also take place in physical as well as chemical changes.
