Question

(a) Define 'mixture'

(b) Why is it necessary to separate the constituents of a mixture ?

(c) State four differences between compounds and mixtures

Answer 1

(a) “Mixtures can be de ned as. a kind of matter which is formed by mixing two or more pure
substances (elements and compounds) in any proportion, such that they do not undergo any chemical
change and retain their individual properties. Therefore they are impure substances.
(b) Because: The mixtures contain unwanted substances which may be harmful and may degrade the
properties of mixtures. So we, need to separated them and extract useful substances.
This is necessary because
(i) It removes unwanted and harmful substances
(ii) to obtain pure and useful substances them.
Example: Sea water is rich in common salt which is an important ingredient of our food to add taste
and nutrients. But sea water, cannot be directly used to get the salt.
Hence, it is necessary to separate both.
(c) Compound
1. A compound is formed from its constituent elements as a result of chemical reaction.
2. A compound is always homogeneous in nature.
3. In a compound the elements are present in a xed ratio by weight.4. The components of a compound can’t be separated by physical methods but can be separated
by chemical methods only.
5. The properties of a compound are different from those of its elements.
6. The formation of a compound from its elements is accompanied by energy changes.
Mixture
1. A mixture is obtained form its (elements, compounds) components as a result of physical
change.
2. The mixtures can be homogeneous or heterogeneous.
3. In a mixture the components can be present in any ratio.
4. The components of a mixture can be separated by physical methods only.
5. The properties of a mixture lie between those of-its components.
6. The formation of a mixture from its constituents is not accompanied by energy changes.