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Tamil Nadu (TNBSE)Class 3 Science★ 5-6 marks in TN Class 3 Term 1 exams — classification exercises, examples from daily life, and short written answers

States of Matter

Samacheer Kalvi (TN State Board) Class 3 Science — Chapter 2, States of Matter. Solids, liquids and gases. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

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By the end of this chapter you'll be able to…

1Define matter as 'anything that has mass and occupies space'
2Name the 3 states of matter: solid, liquid, gas
3Describe properties: solids (fixed shape, fixed volume), liquids (no fixed shape, fixed volume), gases (no fixed shape, no fixed volume)
4Give 3 examples of each state from daily life
5Explain that heating can change solid → liquid (melting) and liquid → gas (evaporation); cooling can reverse these (freezing, condensation)
6Understand that these changes are physical changes — the substance remains the same

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Why this chapter matters

Everything in the universe is matter — the air you breathe, the water you drink, the desk you sit at. This chapter introduces the three states of matter — solid, liquid, gas — with Tamil Nadu-centric examples children can touch and feel: ice (solid), water (liquid), steam (gas). Children learn that heating and cooling can change matter from one state to another, and that these changes are reversible. This is the foundation of chemistry and physics.

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States of Matter — Class 3 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 3 Science, Chapter 2. Solids, liquids and gases.

1. About this chapter

This chapter covers States of Matter as part of the Class 3 Samacheer Kalvi Science curriculum. It deals with solids, liquids and gases and builds conceptual understanding essential for the TN School Term Exam.

By the end of this chapter, students will be able to:

Describe properties of solids, liquids and gases
Give everyday examples of each state

2. Key concepts

Concept 1: Describe properties of solids, liquids and gases.
Concept 2: Give everyday examples of each state.

3. Important terms and formulas

Term / Formula	Description
Describe properties of solids,…	Describe properties of solids, liquids and gases
Give everyday examples of…	Give everyday examples of each state

4. Worked examples

Example 1. Applying a key concept from this chapter.

Solution: Identify the relevant principle → apply the formula or rule → state the answer with correct units.

Example 2. A typical exam-style question on states of matter.

Solution: Break the problem into steps, use the appropriate formula and verify the answer.

5. Common mistakes

Mistake: Skipping units or forgetting to state them. Fix: Always write units alongside every quantity and answer.
Mistake: Confusing similar terms or concepts in this chapter. Fix: Make a comparison table of the terms during revision.

6. Practice (exam-style)

Define the main term or principle covered in Chapter 2.
Give two real-life examples related to states of matter.
Solve a short numerical or descriptive question from this chapter.
State one important formula and explain each symbol.

7. Answer key (hints)

Refer to section 2 (Key concepts) above for the definition.
Examples should be drawn from daily experience and local context.
Apply the formula from section 3, show all steps clearly.
Formula with units — refer to the textbook glossary for symbol meanings.

8. Quick revision

Class 3 Science — Chapter 2: States of Matter.
Core idea: Solids, liquids and gases.
Key outcomes: Describe properties of solids, liquids and gases; Give everyday examples of each state.
Always revise diagrams / tables from the Samacheer Kalvi textbook before the exam.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Three states of matter

Solid → fixed shape, fixed volume. Particles packed tightly, cannot move freely. Examples: stone, ice, wood, book, pencil, eraser. Liquid → no fixed shape (takes shape of container), fixed volume. Particles close but can slide past each other. Examples: water, milk, oil, juice, petrol. Gas → no fixed shape, no fixed volume (spreads to fill any space). Particles far apart, moving very fast. Examples: air, steam, oxygen, LPG cooking gas.

The same substance can exist in all three states. Water: ice (solid) → water (liquid) → steam (gas). All three are H₂O.

Changing states

Melting: Solid → Liquid (heat added). Example: ice melts into water when left outside the fridge. Freezing: Liquid → Solid (cooled). Example: water kept in freezer becomes ice. Evaporation/Boiling: Liquid → Gas (heated). Example: water in a pan turns into steam when boiled. Condensation: Gas → Liquid (cooled). Example: steam from hot tea hitting a cold lid forms water droplets.

In Tamil Nadu's hot climate, water evaporates quickly from open containers. This is why people use earthen pots (matkas) — evaporation through the pores keeps water cool.

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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT

✗ Thinking gases don't have weight (mass)

✓ All matter has mass, including gases. A filled LPG cylinder is heavier than an empty one because the gas inside has mass. Air also has mass — that is why a balloon filled with air is slightly heavier than an empty balloon.

WATCH OUT

✗ Thinking all liquids are water-like

✓ Honey, oil, milk, and mercury are all liquids but have very different properties. Honey flows slowly (high viscosity). Mercury is a liquid metal. All are liquids because they take the shape of their container.

WATCH OUT

✗ Confusing evaporation and boiling

✓ Evaporation happens slowly at the surface at ANY temperature (water in a puddle dries up even without boiling). Boiling happens throughout the liquid at a specific temperature (100°C for water).

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