Matter is broadly classified into two groups— living and non-living . Non-living matter can further be grouped as pure substances and impure substances.
Elements and compounds are pure substances.
1. A pure substance has uniform composition and properties in all its parts, as it consists of particles of only one kind. For example, sugar and salt are pure substances.
2. It has certain characteristics such as specific temperatures at which it melts and boils. For example, pure water boils at 100°C.
3. The constituents, which make up a pure substance cannot be separated by physical means.
Mixtures are impure substances.
1. A substance is said to be impure if it has particles of other substances mixed in it.
2. The constituents of impure substances may be present in any ratio.
3. The constituents of an impure substance retain their individual properties. For example, the properties of iron and sand do not change when they are mixed together.
4. The constituents of an impure substance can be separated by physical means.