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Tamil Nadu (TNBSE)Class 6 Science★ 6-10 marks in the TN Class 6 Term 3 exam through book-back MCQs, fill-ups, true/false and short answers

Chemistry in Everyday Life

Samacheer Kalvi (TN State Board) Class 6 Science — Term 3 Chapter 3, Chemistry in Everyday Life. Soaps and detergents (saponification), cement and gypsum, plaster of Paris, phenol, fertilizers (NPK) and adhesives, with the actual book-back questions, common mistakes and quick revision.

⏱ 14 min readEasy difficulty✓ Free · NCERT-aligned

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

1Explain how soap is made (saponification)
2State why gypsum is added to cement
3Describe plaster of Paris
4Identify phenol and its use
5Name the primary fertilizer nutrients (NPK)

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Why this chapter matters

Chemistry in Everyday Life links classroom chemistry to soaps, cement, fertilizers and glue we use daily. Saponification, gypsum in cement and NPK are directly tested book-back content in the TN Class 6 Term 3 exam.

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A 5-minute refresher here will save you 30 minutes of confusion below.

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Term 1 — Matter Around Us

Materials.

Chemistry in Everyday Life — Class 6 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 6 Science, Term 3 — Chapter 3. The chemistry behind everyday materials.

1. About this chapter

This chapter covers soaps and detergents, cement and gypsum, plaster of Paris, phenol, fertilizers and adhesives.

2. Soaps and detergents

Soaps were originally made from animal fats and vegetable oils. Saponification is the reaction of fats/oils with a sodium hydroxide solution to make soap.
A soap molecule has a water-loving end and a water-hating end, which lets it clean grease.

3. Cement, gypsum and plaster of Paris

Cement is made from limestone and clay (invented by Joseph Aspdin). Gypsum is added to cement to delay (slow down) its setting.
Plaster of Paris is made by heating gypsum; it sets hard with water and is used in casts and moulds.

4. Phenol, fertilizers and adhesives

Phenol is carbolic acid, used as a disinfectant at low concentration.
Fertilizers supply nutrients; the primary nutrients are NPK — Nitrogen, Phosphorus and Potassium. The earthworm is the farmer's best friend; organic fertilizer is eco-friendly.
Adhesives join (stick) components together. Natural adhesives come from starch; cello tape is an artificial adhesive.

5. Worked examples

Example 1. What alkali is used in saponification? Sodium hydroxide.

Example 2. Why is gypsum added to cement? To delay its setting.

Example 3. What are the three primary fertilizer nutrients? Nitrogen, Phosphorus, Potassium (NPK).

6. Book-back questions (Samacheer Kalvi)

I. Choose the correct answer

Soaps were originally made from — (a) plastics / (b) animal fats and vegetable oils. Ans: (b) animal fats and vegetable oils.
Saponification uses a ____ solution. — (a) hydrochloric acid / (b) sodium hydroxide. Ans: (b) sodium hydroxide.
Gypsum is added to cement for — (a) faster setting / (b) delayed setting. Ans: (b) delayed setting.
Phenol is — (a) carbolic acid / (b) citric acid. Ans: (a) carbolic acid.
Natural adhesives are made from — (a) plastic / (b) starch. Ans: (b) starch.

II. Fill in the blanks 6. The earthworm is called the farmer's best friend. 7. Organic fertilizer is eco-friendly. 8. The primary nutrients in fertilizers are nitrogen, phosphorus and potassium (NPK).

III. True or False 9. Plaster of Paris is made by heating gypsum. — True. 10. Adhesives separate components. — False (they join components). 11. Concentrated phenol is used as a disinfectant. — False (low concentration is used).

7. Common mistakes

Mistake: Saying gypsum makes cement set faster. Fix: Gypsum delays (slows) the setting of cement.
Mistake: Thinking adhesives separate parts. Fix: Adhesives join components together.
Mistake: Forgetting the third NPK nutrient. Fix: The primary nutrients are Nitrogen, Phosphorus and K (Potassium).

8. Quick revision

Term 3 · Ch 3 · chemistry in everyday life.
Soap: fats/oils + sodium hydroxide (saponification); molecule has water-loving and water-hating ends.
Cement (Joseph Aspdin) + gypsum (delays setting); plaster of Paris = heated gypsum.
Phenol = carbolic acid (disinfectant, low concentration); NPK = primary fertilizer nutrients; earthworm = farmer's friend.
Adhesives join parts; natural from starch, artificial like cello tape.

Key formulas & results

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

Saponification

fats/oils + sodium hydroxide -> soap

Makes soap.

Cement

limestone + clay + gypsum (delays setting)

Invented by Joseph Aspdin.

Plaster of Paris

heated gypsum

Sets hard with water.

Fertilizer nutrients

NPK = Nitrogen, Phosphorus, Potassium

Primary nutrients.

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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

✗ Saying gypsum makes cement set faster

✓ Gypsum delays (slows) the setting of cement.

WATCH OUT

✗ Thinking adhesives separate parts

✓ Adhesives join components together.

WATCH OUT

✗ Forgetting the third NPK nutrient

✓ The primary nutrients are Nitrogen, Phosphorus and Potassium.

NCERT exercises (with solutions)

Every NCERT exercise from this chapter — what it covers and how many questions to expect.

Choose the correct answer

Book-back MCQs on soap, saponification, gypsum, phenol and adhesives.

Questions

Fill in the blanks

Earthworm, organic fertilizer and potassium.

Questions

True or False

Plaster of Paris, adhesives and phenol.

Questions

Practice problems

Try each one yourself before tapping "Show solution". Active recall > rereading.

Q1EASY· MCQ

Soaps were originally made from ____.

▶ Show solution

animal fats and vegetable oils.

Q2EASY· MCQ

Saponification uses a ____ solution.

▶ Show solution

sodium hydroxide.

Q3EASY· MCQ

Gypsum is added to cement for ____.

▶ Show solution

delayed setting.

Q4EASY· Fill in the blanks

The ____ is called the farmer's best friend.

▶ Show solution

earthworm.

Q5EASY· True or False

Plaster of Paris is made by heating gypsum. (True/False)

▶ Show solution

True.

Q6MEDIUM· Answer briefly

What are the three primary nutrients supplied by fertilizers?

▶ Show solution

Nitrogen, Phosphorus and Potassium (NPK).

5-minute revision

The whole chapter, distilled. Read this the night before the exam.

•Term 3 Chapter 3 of Samacheer Kalvi Class 6 Science.
•Soaps are made from animal fats and vegetable oils; saponification is the reaction of fats/oils with sodium hydroxide.
•Cement is made from limestone and clay (invented by Joseph Aspdin); gypsum is added to delay its setting.
•Plaster of Paris is made by heating gypsum and sets hard with water.
•Phenol is carbolic acid, used as a disinfectant at low concentration.
•Fertilizers supply NPK (Nitrogen, Phosphorus, Potassium); the earthworm is the farmer's friend; adhesives join components.

Tamil Nadu (TNBSE) marks blueprint

Where the marks come from in this chapter — so you can plan your prep.

Typical chapter weightage: 6-10 marks across book-back MCQ, fill-ups, true/false and short answers

Question type	Marks each	Typical count	What it tests
MCQ / Fill / T-F	1	5-7	Soap, cement, fertilizers
Short Answer	2	1-2	Saponification, NPK

Prep strategy

Remember soap = fats/oils + sodium hydroxide
Note gypsum delays cement setting
Link plaster of Paris to heated gypsum
Learn NPK as primary nutrients

Where this shows up in the real world

This chapter isn't just an exam topic — it lives in the world around you.

Cleaning

Soaps and detergents keep us clean.

Construction

Cement and plaster of Paris build and repair.

Farming

Fertilizers supply nutrients to crops.

Exam strategy

Battle-tested tips from teachers and toppers for this chapter.

State soap = fats/oils + sodium hydroxide
Quote gypsum delays cement setting
Link plaster of Paris to heated gypsum
Name NPK as primary nutrients

Going beyond the textbook

For olympiad aspirants and curious learners — topics that build on this chapter.

Explain how a soap molecule removes grease using its two ends.
Compare organic and inorganic fertilizers.

Where else this chapter is tested

CBSE board isn't the only one — other exams test this chapter too.

TN Class 6 Term 3 ExamHigh

NMMS / Foundation ScienceMedium

School unit testsHigh

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Questions students ask

The real ones — pulled from the Q&A community and tutor sessions.

Saponification is the chemical reaction in which fats or oils react with an alkali like sodium hydroxide to form soap; it is how soap is manufactured.

Gypsum is added to cement to slow down or delay its setting, giving workers enough time to mix, pour and shape the cement before it hardens.

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