NCERT 6th Class (CBSE) Science: Separation of Substances

Question: What is the difference between homogeneous and heterogeneous mixture? Give an example of each mixture.

Answer: Homogeneous mixture:

1. Mixtures in which constituents are uniformly spread.
2. Each part of the mixture has same properties.
3. Fore example sugar in water, air, soft drinks.

Heterogeneous mixture:

1. Mixtures in which constituents are not uniformly spread.
2. Each part of mixture does not has same properties.
3. For example sand, iron, biryani.

Question: We always talk about a saturated solution at temperature? Why is the temperature specified?

Answer: Saturated solution on heating becomes unsaturated and on cooling it becomes over saturated. So it is necessary to specified the temperature.

Question: Under which condition can handpicking be used to separate the constituents of a mixture?

Answer: 

1. Mixture in small amount
2. Impurity in small amount
3. Difference of colour, shape, size
4. Impurity is big enough to pick by hand

Question: How will you separate a mixture of grass, pebbles and sand?

Answer: We will separate the mixture by:

1. Sieving: We will separate sand from mixture by sieving.
2. Winnowing: We will separate grass and pebbles by winnowing.