Lesson 1 of 12 · 7 min
Classifying matter
NCERT § "Nature of Matter"
On one kitchen counter: Diya's tumbler of water, a second glass with sugar stirred in, and a third with a pinch of sand at the bottom. Chemistry puts these three glasses in three different boxes.
The lesson in notes
In short
Whatever has mass and takes up room counts as matter; it exists as solids (definite shape and volume), liquids (definite volume, no definite shape) and gases (neither definite shape nor volume).
The three states can be interconverted by changing temperature and pressure; heating a solid gives a liquid, and heating a liquid gives a gas.
At the macroscopic level matter is split into mixtures and pure substances.
A homogeneous mixture has the same composition throughout, such as sugar dissolved in water or air; a heterogeneous mixture does not, such as a mixture of salt and sand.
Components of a mixture keep their own properties and can be separated by physical methods like filtration, crystallisation or distillation.
Pure substances are either elements, made of only one kind of atom, or compounds, in which atoms of two or more elements are joined in a fixed ratio.
A compound's properties differ from those of its constituent elements, and it can be broken into its elements only by chemical methods; water, for example, is unlike hydrogen or oxygen.