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Tamil Nadu (TNBSE)Class 3 Science★ 4-5 marks in TN Class 3 Term 1 exams — identifying kitchen science, household applications, and safety rules

Science in Everyday Life

Samacheer Kalvi (TN State Board) Class 3 Science — Chapter 4, Science in Everyday Life. Simple machines and tools. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

⏱ 10 min readEasy difficulty✓ Free · NCERT-aligned

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

1Identify science in everyday kitchen activities: boiling (liquid to gas), freezing (liquid to solid), fermentation (idli/dosa batter rising)
2Explain how a pressure cooker works in simple terms: increased pressure → higher temperature → faster cooking
3Identify simple machines at home: lemon squeezer and bottle opener as levers, knife as a wedge, stairs as an inclined plane
4List 3 kitchen safety rules: do not touch hot vessels with bare hands, keep flammable items away from flame, use a cloth to hold hot handles
5List 3 home safety rules: do not touch electrical items with wet hands, do not fly kites near power lines, keep floors dry to avoid slipping

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Why this chapter matters

Science is not confined to labs — it happens in every kitchen, every home, every day. This chapter makes children see the science in familiar activities: why idli/dosa batter ferments and rises (microorganisms produce gas), why water boils and turns to steam (change of state), why a pressure cooker cooks faster (increased pressure raises boiling point), and how simple tools like a lemon squeezer and bottle opener work (levers). It connects the abstract concepts of the previous three chapters — my body, states of matter, force — to concrete daily experiences. The chapter also teaches kitchen and home safety, which can prevent real accidents.

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Science in Everyday Life — Class 3 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 3 Science, Chapter 4. Simple machines and tools.

1. About this chapter

This chapter covers Science in Everyday Life as part of the Class 3 Samacheer Kalvi Science curriculum. It deals with simple machines and tools and builds conceptual understanding essential for the TN School Term Exam.

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

Identify science in daily activities
Explain how simple machines make work easier

2. Key concepts

Concept 1: Identify science in daily activities.
Concept 2: Explain how simple machines make work easier.

3. Important terms and formulas

Term / Formula	Description
Identify science in daily…	Identify science in daily activities
Explain how simple machines…	Explain how simple machines make work easier

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 science in everyday life.

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 4.
Give two real-life examples related to science in everyday life.
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 4: Science in Everyday Life.
Core idea: Simple machines and tools.
Key outcomes: Identify science in daily activities; Explain how simple machines make work easier.
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.

Kitchen science

Boiling → water turns into steam (liquid → gas) at 100°C. Freezing → water turns into ice (liquid → solid) at 0°C. Fermentation → microorganisms (yeast/bacteria) in idli/dosa batter produce gas bubbles that make the batter rise and become fluffy. Dissolving → salt/sugar disappear in water but are still there (the water tastes salty/sweet).

Idli is a marvel of food science: the fermentation of rice and urad dal batter not only makes it fluffy but also increases B-vitamins and makes it easier to digest. This traditional knowledge is centuries old.

How a pressure cooker works

A pressure cooker is sealed tight → steam cannot escape → pressure inside increases → water boils at a higher temperature (above 100°C) → food cooks faster. The weight/whistle on top releases excess steam to prevent explosion.

The pressure cooker was invented in 1679 but became an Indian kitchen staple only in the 20th century. It saves fuel and time — a dal that takes 45 minutes in an open pot takes only 10-15 minutes in a pressure cooker.

Simple machines at home

Lever → a rigid bar that rotates around a fixed point (fulcrum). Examples: lemon squeezer, bottle opener, scissors (two levers), seesaw. Wedge → a triangular tool that splits things apart. Examples: knife, axe, nail tip. Inclined plane → a slanted surface. Examples: stairs, ramp, slide in a park.

These are all 'simple machines' — tools that make work easier by multiplying or changing the direction of force. Complex machines like cars and washing machines are made of many simple machines working together.

Safety rules — Kitchen and Home

Kitchen: Use a dry cloth to hold hot handles. Turn pot handles inward so they cannot be knocked off the stove. Keep flammable items (plastic, cloth, paper) away from the flame. Do not run in the kitchen. Home: Never touch electrical items with wet hands — water conducts electricity. Do not fly kites near overhead power lines — wet kite string (manja) can conduct electricity. Keep floors dry to avoid slipping. Know emergency numbers: 108 (ambulance), 101 (fire).

Most home accidents are preventable. A child who learns these rules at age 8-9 is safer for life. The simple rule 'wet hands + electricity = danger' alone can save lives.

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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

✗ Touching electrical switches with wet hands

✓ Water conducts electricity — it creates a path for current to flow through your body. This can cause severe electric shock or death. Always dry your hands completely before touching any switch, plug, or appliance.

WATCH OUT

✗ Opening a pressure cooker immediately after turning off the flame

✓ The cooker is still under high pressure and full of superheated steam. Opening it immediately can cause a steam explosion. Always let it cool, wait for the pressure to release naturally, OR carefully lift the weight to release steam BEFORE opening.

WATCH OUT

✗ Mixing cleaning chemicals (like toilet cleaner and bleach) out of curiosity

✓ Mixing household chemicals can produce toxic gases that can be deadly. Never mix any cleaning products. If you need to clean, use one product at a time, and always with adult supervision.

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