You are already familiar with the term matter from your earlier classes. Anything which has mass and occupies speed is called matter.
Everything around for example, book, pen 🖊️, pencil ✏️, water, air, all living beings etc, are composed of matter. You know that they have mass and they occupy space.
You are also aware that matter can exist in three physical states viz. Solid, liquid and gas.
The constituent particles of matter in these three states can be represented as shown in picture. In solid, these particles are held very close to each other in an orderly fashion and there is not much freedom of movement.
In luquid, the particles are close to each other but they can move around. However, in gases, the particles are far apart as compared to those present in solid or liquid states and their movement is easy and fast.
Because of such arrangement of particles different states of matter exhibit the following characteristics:
(1). Solid have definete volume and definite shape.
(2). Liquids have definete volume but not the definite shape. They take the shape of the container in which they are placed.
(3). Gases have neither definite volume nor definte shape. They completely occupy the container in which they are placed.
These three states of matter are interconvertible by changing the conditions of temperature and pressure.
Solid⇌ luquid⇌Gas
On heating a solid usually changes to a liquid and the liquid on further heating changes to the gaseous (or vapour) state. In the reverse process, a gas on cooling liquified the reverse process, a gas on cooling liquified to the luquid and the luquid on further cooling freezes to the solid.
At the macroscopic or bulk level, matter can be classified as mixtures or pure substances. Many of the substances present around you are mixture. For example, surgar solution in water, air, tea etc., are all mixture. A mixture contains two or more substances present in it (in any ratio) which are called it's components.
A mixture may be homogeneous or heterogeneous. In a homogeneous mixture the components completely mix with each other and it's composition is uniform throughout.
Sugar solution, and air are thus, the examples of homogeneous mixture. In contrast to this, in Hatrogeneous mixture.
