ICSE ICSE Class 8 - CISCE Question Bank Solutions for Chemistry

Potassium chloride is added to water and stirred. A salt solution is obtained, which is then boiled, leaving behind a residue.

1. Is the above change physical or chemical?
2. Name the residue which remains behind after the salt solution is boiled.
3. Is the change reversible or not reversible?
4. Are the composition and properties of the original substance altered?
5. Give a reason why the above experimentation would not be possible if calcium carbonate was taken in place of potassium chloride.

Give a reason why – Heating a platinum wire is a reversible change but, heating a magnesium wire is an irreversible change.

Give a reason why – Addition of zinc nitrate to water is a physical change but, the addition of zinc to dilute nitric acid is a chemical change.

Give a reason why rusting of iron is a chemical change but, the magnetization of iron is a physical change.

Select the chemical changes from the following list of changes

Vaporisation of water into water vapour.

Select the chemical changes from the following list of changes

Boiling of milk. 

Select the chemical changes from the following list of changes

Respiration in mammals.

Select the chemical changes from the following list of changes

Rotting of eggs.

Select the chemical changes from the following list of changes

Drying of a fruit

Select the chemical changes from the following list of changes

The carbon cycle.

Select the chemical changes from the following list of changes

The occurrence of lightning.

Select the chemical changes from the following list of changes

Breaking of glass

Select the chemical changes from the following list of changes

Butter turning rancid

Select the chemical changes from the following list of changes

Glowing of an electric bulb.

Select the chemical changes from the following list of changes

The crystallisation of salt from its solution.

Select the chemical changes from the following list of changes

Change of seasons

Select the chemical changes from the following list of changes

Preparation of carbon dioxide from calcium carbonate & dilute hydrochloric acid.

Select the correct answer from the choice given below to complete the sentence

A change in which a substance retains its identity is a

______ change.

Select the correct answer from the choice given below to complete the sentence

The matter is added or removed during a ____________  change.

Select the correct answer from the choice given below to complete the sentence

The energy required for completion of a physical change is ______________ when the change is reversed.