This chapter tells the students about the source from where our universe is created, i.e. matter.
Indian philosophers state that matter consists of 5 basic elements – the "Panch Tatva"- air, earth, fire, sky, and water. According to them, every living or non-living thing is formed of these five elements. Modern-day scientists classify matter based on its physical properties and chemical nature. In the view of physical nature, there are two theories, i.e. matter is either made from a continuous sort of a block of wood or created of particles like sand. Matter consists of millions of tiny particles, as shown in an experiment of some crystals of permanganate of potash which keep on dividing themselves into smaller and smaller particles. The experiment shows that the matter has space present in it and has kinetic energy too. That's why the colour of permanganate of potash goes on. Particles in the matter have the force of attraction too.
We are surrounded by matter, and it usually exists in three phases: solid, liquid, and gas. The state's classification arises due to the variation within the characteristic of the particles of matter. The solids are categorised based on fixed shape, distinct boundaries, and negligible change in volumes, i.e., negligible compressibility. The liquids do not have any fixed shape but have fixed volume. On the other hand, the gases are highly compressible compared to solid and liquid, and liquids have no fixed shape. In terms of force of attraction between the particles:
In terms of the interparticle spaces, these phases follow the ascending pattern in solids, liquids and gases. The kinetic energy of the particles is least in the case of solids and highest in gases. The kinetic energy in the case of liquids lies somewhere between them.
The phases of matter are interconvertible, i.e. they can be altered by altering either temperature or pressure. One special case of phase change is Sublimation. It is the phase change of a solid to a gas when it converts without going through the liquid state. The melting point is the temperature at which the kinetic energy is higher than the strength of the force of attraction between the particles. Evaporation is defined as the phase change of a liquid into vapour at any temperature below its boiling point. The evaporation causes cooling because the particles of liquids absorb energy from the environment (surroundings) to regain the energy lost during evaporation. The evaporation rate depends on the surface, the temperature of the encircling (surrounding), humidity, and wind speed. Latent heat of vaporisation is defined as the heat energy needed to change a unit mass of liquid into its gases phase at its boiling point. The Latent heat of fusion is defined as the amount of energy needed to convert a unit mass of solid into liquid when the temperature equalises the melting point. The pressure needs to be the atmospheric pressure in both cases.