Chapter 7: Particulate Nature of Matter
Original notes — ready CBSE (NCERT, English Medium) • Class 8 • Science • Book: Curiosity
Chapter 7: Particulate Nature of Matter — EG's own notes, in simple words
Book: Curiosity (CBSE, Class 8) | Chapter 7 | Medium: English
Diagram (labels are printed on the image): Diagram (labels are printed on the image): particles in the three states of matter — tightly packed in a solid, looser in a liquid, and far apart in a gas. A general picture, not a diagram from the book.
Ink spreading slowly through water. A general picture about particles moving, not a book scene.
What the chapter is about
Everything around us is made of matter, and matter is made of tiny particles. These particles are too small to see, but their behaviour explains a lot: why solids keep their shape, why liquids flow, and why gases spread everywhere.
Particles of matter have space between them, and they are always moving. In a solid, particles are packed tightly and only vibrate in place, so a solid keeps its shape. In a liquid, particles have more space and can slide past each other, so a liquid flows. In a gas, particles are far apart and move freely and fast, so a gas fills its whole container.
Particles also attract each other. The attraction is strongest in solids and weakest in gases. When we heat matter, its particles move faster and the spaces between them grow — that is why most things expand on heating. Diffusion, like the smell of food spreading through a room, is particles moving from where there are many of them to where there are fewer.
What you should learn
Notice that matter is made of tiny moving particles with space between them, and how this explains the three states, expansion on heating and diffusion.
Key Terms
- Particle — A tiny unit of matter; all matter is made of particles.
- Diffusion — The spreading of particles from a region of higher concentration to a region of lower concentration.
- Intermolecular space — The empty space between particles of matter.
- Intermolecular force — The force of attraction between particles of matter.
- State of matter — One of the forms of matter: solid, liquid or gas, decided by how its particles are arranged and move.
Remember
- Matter is made of tiny particles that are always moving.
- Particles have space between them and attract each other.
- Solids: tightly packed, fixed shape. Liquids: flow. Gases: spread to fill space.
- Heating makes particles move faster and increases the space between them.
Exam Tip / Common Mistake
Common mistake: saying particles stop moving in a solid. They do not stop — they vibrate in their fixed places. Only their positions are fixed, not their motion.
Chart / Table: Particles in the three states
| Point | Detail |
|---|---|
| Solid | Tightly packed; vibrate in place; fixed shape and volume |
| Liquid | Looser; slide past each other; fixed volume, no fixed shape |
| Gas | Far apart; move freely and fast; no fixed shape or volume |
| Heating | Particles move faster; spaces grow; matter expands |
| Cooling | Particles move slower; spaces shrink; matter contracts |
Practice set — try it yourself
- What is meant by the particulate nature of matter?
Hint: Think about tiny particles. - Why does a gas fill the whole container?
Hint: Think about particle spacing and motion. - Why can a liquid be poured but a solid cannot?
Hint: Think about how particles move in each. - What is diffusion? Give one example.
Hint: Think about smell spreading. - Why do railway tracks have small gaps?
Hint: Think about expansion on heating.
Questions with Answers
- What does it mean to say matter is particulate?
It means all matter is made of tiny particles. These particles are too small to see, but they have space between them, they attract each other, and they are always moving. - Why does a solid have a fixed shape but a liquid does not?
In a solid, particles are tightly packed and held strongly, so they only vibrate in place and the shape stays fixed. In a liquid, particles can slide past each other, so the liquid flows and takes the shape of its container. - What is diffusion? Give an example.
Diffusion is the movement of particles from a place where there are many of them to a place where there are fewer. The smell of food spreading from the kitchen to other rooms is diffusion of food particles in air. - Why does matter expand on heating?
Heating gives particles more energy, so they move faster and push further apart. The spaces between particles grow, so the whole object expands. - Why can we smell a perfume from across the room?
Perfume particles mix with air particles and diffuse through the room. Because gas particles move freely and fast, the smell spreads quickly in all directions.
How to use this page: Read the summary, say the Key Terms in your own words, then try the practice set without looking. Use the Questions with Answers to check yourself afterwards. Ask your teacher or parent to check your answers.