§1. The Composition, Structure and States of Matter

A Grade 8 Physics topic: «The Composition, Structure and States of Matter» (pp. 6–11, E. Mambetakunov and others). Matter is the objective reality that acts on our senses but exists independently of our consciousness; it exists in two forms, substance and field. The states of matter are solid, liquid, gas and plasma. A molecule is the particle that carries all the properties of a substance; in Latin the word means «a small mass». The ancient Greek scholar Democritus gave the smallest particle of a substance the name «atom», while Maxwell, Boltzmann, Clausius, Brown and Stern determined the size of the atom (10⁻⁸ cm) and its mass. The protons and neutrons that make up the nucleus are together called nucleons. M. Lomonosov's three statements form the basis of the kinetic molecular theory. In 1827 R. Brown watched coloured grains placed in water. Diffusion is the mixing of the molecules of substances that touch one another; it is fast in gases, slower in liquids and very slow in solids.