Chapter focus
Use a particle model to explain why matter has mass and occupies space, and how particles behave in different states.
These are original study notes and practice questions prepared for revision. Use your assigned NCERT edition for the complete lesson, diagrams, activities, and exercise wording.
What you will learn
- Explain the main idea: Use a particle model to explain why matter has mass and occupies space, and how particles behave in different states.
- Use the key terms and relationships in the notes below.
- Show your reasoning and check whether an answer fits the question.
Key ideas and notes
- Matter is made of tiny particles with spaces between them.
- Particles move; heating generally increases their motion.
- Solids keep shape, liquids flow but keep volume, and gases spread to fill their container.
Worked example
A scent spreading through a room is diffusion: particles move and mix through air.
Quick revision
Matter is made of tiny particles with spaces between them.
Particles move; heating generally increases their motion.
Solids keep shape, liquids flow but keep volume, and gases spread to fill their container.
Original practice questions
Try each question first. Open the answer to check your reasoning.
Which state is easiest to compress: solid, liquid, or gas?
Answer: Gas.
What happens to particle motion when a substance is warmed?
Answer: It generally increases.
Why does a liquid take the shape of its container?
Answer: Its particles can move past one another while remaining close together.
Chapter summary
Use a particle model to explain why matter has mass and occupies space, and how particles behave in different states. The key ideas above give you a short revision path; practise explaining them in your own words and revisit any step you could not justify.