NCERT 6th Class (CBSE) Science: Sorting Materials into Groups

Question: What is the basis for sorting materials?

Answer: Materials are grouped on the basis of similarities or dissimilarities in their properties.

Question: What is the reason for grouping materials?

Answer: Materials are grouped for our convenience to study their properties and also observe any patterns in these properties.

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

Answer: Metals when exposed to air react with moisture and gases present in it, thereby forming a dull layer of some other compound on it.

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

Answer: The molecules of water do not intermingle (mix) with the molecules of oil. The space between the molecules of water is not taken by oil, so they are immiscible in water.

Question: Name a non-metal that has lustre.

Answer: Iodine.

Question: 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.

Answer: Mercury is a metal that exists in liquid state. Sodium and Potassium are soft metals and can be cut with knife.

Question: Name the naturally occuring hardest substance known.

Answer: Diamond, it is made up of carbon (non-metal).

Question: Why is water called a universal solvent?

Answer: Water dissolves a large number of substances in it. So it is called universal solvent.

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

Answer: Proper grouping of objects helps shopkeeper in the following ways:

1.  He can locate the required object easily and quickly.
2.  He can easily come to know what stocks are going to finish and he should purchase them for his customers.