What is Solutions Exercises in Class 8 Science NCERT?

The Class 8 Science NCERT Chapter 9 — Amazing World of Solutes, Solvents and Solutions exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, solubility questions, concentration questions, competency-based questions. It includes multiple-choice qu…

What does the NCERT Class 8 Science Amazing World of Solutes, Solvents and Solutions exercise section cover?

The Class 8 Science NCERT Chapter 9 u2014 Amazing World of Solutes, Solvents and Solutions exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, solubility questions, concentration questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Amazing World of Solutes, Solvents and Solutions exercises?

Class 8 students should approach the Amazing World of Solutes, Solvents and Solutions exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and solubility questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Amazing World of Solutes, Solvents and Solutions questions competency-based as per NEP 2020?

Yes, the Amazing World of Solutes, Solvents and Solutions exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 9 exercises?

The Chapter 9 u2014 Amazing World of Solutes, Solvents and Solutions exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, solubility questions, concentration questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Amazing World of Solutes, Solvents and Solutions exercise set present two statements u2014 an Assertion (A) and a Reason (R) u2014 and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Amazing World of Solutes, Solvents and Solutions exercises is to read through all theory parts of NCERT Curiosity Chapter 9 once, write down the key terms such as NCERT exercises, solubility questions, concentration questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions u2014 first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

What does the NCERT Class 8 Science Amazing World of Solutes, Solvents and Solutions exercise section cover?

The Class 8 Science NCERT Chapter 9 — Amazing World of Solutes, Solvents and Solutions exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, solubility questions, concentration questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Amazing World of Solutes, Solvents and Solutions exercises?

Class 8 students should approach the Amazing World of Solutes, Solvents and Solutions exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and solubility questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Amazing World of Solutes, Solvents and Solutions questions competency-based as per NEP 2020?

Yes, the Amazing World of Solutes, Solvents and Solutions exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 9 exercises?

The Chapter 9 — Amazing World of Solutes, Solvents and Solutions exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, solubility questions, concentration questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Amazing World of Solutes, Solvents and Solutions exercise set present two statements — an Assertion (A) and a Reason (R) — and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Amazing World of Solutes, Solvents and Solutions exercises is to read through all theory parts of NCERT Curiosity Chapter 9 once, write down the key terms such as NCERT exercises, solubility questions, concentration questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions — first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

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Solutions — Exercises

🎓 Class 8 Science CBSE Theory Ch 9 — Reaching the Age of Adolescence ⏱ ~20 min

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Chapter 9 — Summary

In this chapter we explored how two or more substances can mingle so smoothly that they look like a single substance. We met solutes, solvents, looked at the many faces of solutions, and learnt how to tell a true solution apart from a colloid or a suspension.

Solution

A homogeneous mixture of two or more substances. Always = solute + solvent.

Solute & Solvent

Solute is the substance that dissolves; solvent is the one that does the dissolving (usually in larger amount).

Types of Solutions

Can be gas-gas (air), gas-liquid (cola), liquid-liquid (vinegar), solid-liquid (salt water), solid-solid (brass) and more.

Miscible / Immiscible

Liquids that mix freely (water + alcohol) vs those that stay in layers (oil + water).

Solubility

Max solute that dissolves in 100 g of solvent at a given temperature.

Saturation

Unsaturated (less) → Saturated (max) → Supersaturated (more than max; unstable).

Factors

Nature of solute-solvent, Temperature (solids ↑ with T, gases ↓ with T), Pressure (gases only).

Concentration

Dilute vs concentrated. Mass % = (mass solute / mass solution) × 100.

Universal Solvent

Water dissolves more substances than any other liquid because it is polar.

Solution vs Colloid vs Suspension

Distinguished by particle size, clarity, settling and Tyndall effect.

Tyndall Effect

Scattering of light by colloidal particles — makes a torch beam visible through milk, fog or smoke.

Everyday Examples

Sea water, lemonade, air, brass, cola, milk, fog, muddy water — every mixture tells a story.

Key Terms (Keyword Grid)

SolutionHomogeneous mixture of solute and solvent.

SoluteSubstance that dissolves; usually smaller amount.

SolventSubstance that dissolves the solute; usually larger amount.

MiscibleLiquids that form a single clear layer when mixed.

ImmiscibleLiquids that do not mix; form separate layers.

SolubilityMax g of solute per 100 g solvent at a given temperature.

SaturatedSolution that has dissolved its maximum solute.

UnsaturatedSolution that can dissolve more solute.

SupersaturatedHolds more than the normal maximum — unstable.

DiluteSolution with little solute.

ConcentratedSolution with a large amount of solute.

Mass %(Mass of solute ÷ Mass of solution) × 100.

Universal SolventWater — dissolves more substances than any other liquid.

SuspensionHeterogeneous mixture with visible particles that settle.

ColloidMixture with medium-sized particles that scatter light.

Tyndall EffectScattering of light by colloidal particles.

AlloySolid solution of two or more metals (e.g. brass).

Polar moleculeMolecule with + and − ends (e.g. water).

NCERT-Style Exercises

Try each question on your own first, then click Show Solution to check.

Q1. Fill in the blanks: (a) A mixture of two miscible liquids is a ______ solution. (b) Air is mainly a solution of oxygen in ______. (c) Solubility of a gas in water ______ with rise in temperature. (d) Water is called the ______ solvent.

Solution: (a) liquid-liquid / homogeneous, (b) nitrogen, (c) decreases, (d) universal.

Q2. Classify the following mixtures as true solution, colloid or suspension: (i) sugar in water, (ii) milk, (iii) chalk in water, (iv) air, (v) fog, (vi) muddy river water, (vii) brass.

Solution: (i) True solution, (ii) Colloid, (iii) Suspension, (iv) True solution (gas-gas), (v) Colloid, (vi) Suspension, (vii) True solution (solid-solid / alloy).

Q3. Identify solute and solvent in each: (a) Iodine tincture, (b) Sugar syrup, (c) Aerated water (soda), (d) Brass, (e) Air.

Solution:

(a) Iodine (solute) in alcohol (solvent).
(b) Sugar (solute) in water (solvent).
(c) Carbon dioxide gas (solute) in water (solvent).
(d) Zinc (solute) in copper (solvent) — copper is the major metal.
(e) Oxygen + other gases (solutes) in nitrogen (solvent).

Q4. 15 g of common salt is dissolved in 135 g of water. Calculate the mass percentage of salt in the solution.

Solution: Mass of solution = 15 + 135 = 150 g. Mass % of salt = (15 ÷ 150) × 100 = 10%.

Q5. The solubility of potassium nitrate at 30 °C is 45 g per 100 g of water. Rahul dissolves 60 g of KNO₃ in 100 g of water at 30 °C. (a) How much will dissolve? (b) How much remains undissolved? (c) Is the resulting solution saturated?

Solution: (a) Only 45 g will dissolve (the solubility limit). (b) 60 − 45 = 15 g will remain at the bottom as undissolved solid. (c) Yes, the liquid portion is a saturated solution at 30 °C, since it has dissolved the maximum it can.

Q6. Why does a bottle of cola fizz more when opened on a warm day than on a cold day?

Solution: The solubility of a gas in a liquid decreases as temperature rises. A warm bottle holds CO₂ less tightly, so on releasing pressure (opening the cap) more gas escapes at once — producing a larger fizz. A chilled bottle retains more CO₂ and fizzes gently.

Q7. Define the Tyndall effect and give two everyday examples.

Solution: The Tyndall effect is the scattering of a light beam by the tiny particles present in a colloid, which makes the path of the beam visible. Examples: (i) The glowing beam of a cinema projector or car headlight in a smoky/dusty room. (ii) Sunbeams streaming through the canopy of a forest on a misty morning.

Q8. Differentiate between true solution, colloid and suspension in tabular form (any four points).

Solution:

Property	True Solution	Colloid	Suspension
Particle size	< 1 nm	1–1000 nm	> 1000 nm
Appearance	Clear	Translucent	Opaque / turbid
Settling on standing	Never	Rarely	Settles
Tyndall effect	No	Yes	Particles visible
Example	Salt water	Milk	Muddy water

Q9. Why is water called the "universal solvent"? Mention two substances that it cannot dissolve.

Solution: Water is polar — its molecules have positive and negative ends — and therefore it dissolves a very wide range of ionic and polar solutes (salt, sugar, acids, many gases, vitamins, etc.). No other liquid matches this range, so water earns the title "universal solvent". However, it still cannot dissolve non-polar substances such as cooking oil and candle wax.

Q10. Explain, with particle-level reasoning, why ice added to a glass of hot water melts very rapidly.

Solution: The water particles in hot water move with high kinetic energy. When they collide with the rigidly arranged particles of ice, they transfer this energy, loosening the inter-particle attraction that held the ice together. The surface ice particles break free, turn into liquid and mix quickly with the surrounding hot water — the cube melts rapidly.

Q11. State whether true or false. Correct the false ones. (a) A supersaturated solution is very stable. (b) Air is a homogeneous mixture. (c) Pressure strongly affects the solubility of solids in water. (d) The Tyndall effect is shown by true solutions.

Solution:

(a) False. Supersaturated solutions are unstable — a slight disturbance makes the extra solute crystallise out.
(b) True. Air has the same composition in every puff — it is a gas-in-gas solution.
(c) False. Pressure has a negligible effect on solids and liquids; it mainly affects the solubility of gases in liquids.
(d) False. The Tyndall effect is shown by colloids, not true solutions — particles in true solutions are too small to scatter light.

Q12. A student prepares three salt-water samples: (A) 10 g in 200 g water, (B) 10 g in 100 g water, (C) 20 g in 100 g water. Arrange them in order of increasing concentration and calculate their mass percentages.

Solution:

A: mass of solution = 210 g; mass % = (10/210) × 100 ≈ 4.76%.
B: mass of solution = 110 g; mass % = (10/110) × 100 ≈ 9.09%.
C: mass of solution = 120 g; mass % = (20/120) × 100 ≈ 16.67%.

Order of increasing concentration: A < B < C.

You have completed Chapter 9! Revisit Parts 1–3 to re-read any section you found tricky, try the activities at home (with adult help where needed), and you will be ready for any question examiners can throw at you on the amazing world of solutions.

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