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 story this chapter follows: Diya's tumbler of water

Diya pours water into a steel tumbler on her mother's kitchen scale: 180 mL, 180 g. That one glass holds 10 moles of water, 6.022 × 10²⁴ molecules, and the same water could be made from 20 g of hydrogen and 160 g of oxygen. Every idea in this chapter, from units to limiting reagents, is a question asked about that tumbler.

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.