What is the reason for grouping materials?

‘Grouping of objects helps the shopkeeper.’ Justify the statement.

Why is water called a universal solvent?

Name the naturally occuring hardest substance known.

Metals generally occur in solid state and are hard. Name a metal that exists in liquid state and a metal that is soft and can be cut with knife.

Name a non-metal that has lustre.

Kerosene, coconut oil, mustard oil do not dissolve in water, even on shaking. They separate after sometime forming two different layer. Explain why.

Metals have lustre (shine). Give reason why some metal articles become dull and loose their shine.

What is the basis for sorting materials?

Why is water important for our body?

Mention some materials which are made up of paper.