Matter is made up of extremely small particles called atoms or molecules. These particles are so tiny that they cannot be seen with the naked eye. They have some important characteristics: they are in constant motion, they have spaces between them, and they attract each other with varying degrees of force. The motion of these particles increases with temperature, which explains processes like diffusion and expansion of matter on heating.
The particulate nature of matter can be observed through simple activities such as dissolving sugar or salt in water, the spreading of ink or potassium permanganate in water, and the smell of perfume spreading in a room. These activities show that particles of matter are continuously moving and have space between them. The arrangement of these particles is different in solids, liquids, and gases, which gives each state of matter its unique properties. This concept helps us understand the behaviour of matter in our daily life.
Key Points
- Matter is made up of tiny particles called atoms or molecules.
2. These particles are too small to be seen with the naked eye.
Characteristics of particles of matter:
- They have space between them (intermolecular space).
- They are in constant motion (possess kinetic energy).
- They attract each other with intermolecular forces.
Diffusion is the mixing of particles of two substances on their own due to motion, e.g., spreading of perfume, mixing of salt in water.
Particles of matter move faster when heated, as heat increases their kinetic energy.
The arrangement of particles is different in solids, liquids, and gases:
- Solids → particles tightly packed, strong force of attraction.
- Liquids → particles loosely packed, weaker force, can flow.
- Gases → particles far apart, negligible force of attraction, move freely.
Evidence for particulate nature includes: dissolving sugar or salt in water, spreading of ink in water, smell of food or perfume spreading in air.
