CBSE Class 8 Science Chapter 9: The Amazing World of Solutes, Solvents, and Solutions — Assertion & Reason
CBSE Class 8 Science Assertion & Reason
Expert crafted · Instant PDF download · 2026-27
The following Assertion and Reason questions are based on Chapter 9: The Amazing World of Solutes, Solvents, and Solutions from the NCERT Class 8 Science textbook Curiosity. Each question has four options — read both the Assertion (A) and Reason (R) carefully before selecting your answer.
How to attempt Assertion & Reason questions:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Assertion & Reason Questions
1
Assertion (A): A mixture of salt and water is called a solution.
Reason (R): Salt and water form a uniform mixture where the components are evenly distributed throughout.
Reason (R): Salt and water form a uniform mixture where the components are evenly distributed throughout.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. A uniform mixture, where the solute dissolves completely and evenly into the solvent, is scientifically termed a solution.
2
Assertion (A): Air is considered a gaseous solution where nitrogen acts as the solvent.
Reason (R): Nitrogen is present in the largest amount in the air, while other gases like oxygen and carbon dioxide act as solutes.
Reason (R): Nitrogen is present in the largest amount in the air, while other gases like oxygen and carbon dioxide act as solutes.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. In a solution, the substance present in the larger amount is the solvent, which makes nitrogen the solvent in the Earth's atmosphere.
3
Assertion (A): When no more salt can be dissolved in a glass of water at room temperature, it becomes an unsaturated solution.
Reason (R): A saturated solution is one in which the maximum amount of solute has been dissolved at a given temperature.
Reason (R): A saturated solution is one in which the maximum amount of solute has been dissolved at a given temperature.
Answer: (d)
A is false, but R is true. A solution that cannot dissolve any more solute at a particular temperature is called a saturated solution, not an unsaturated one.
4
Assertion (A): A saturated solution of baking soda at 20°C can dissolve more baking soda if it is heated to 50°C.
Reason (R): For most solid substances, solubility in water increases with an increase in temperature.
Reason (R): For most solid substances, solubility in water increases with an increase in temperature.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Heating a saturated solution increases its capacity to dissolve solute, effectively turning it back into an unsaturated solution at the higher temperature.
5
Assertion (A): Aquatic life gets more dissolved oxygen in warm water than in cold water.
Reason (R): The solubility of gases in liquids generally decreases as the temperature of the liquid increases.
Reason (R): The solubility of gases in liquids generally decreases as the temperature of the liquid increases.
Answer: (d)
A is false, but R is true. Cold water holds more dissolved oxygen than warm water. Because gas solubility drops as water warms up, aquatic life can actually struggle to get enough oxygen in warm water.
6
Assertion (A): A piece of iron feels heavier than a piece of wood of the exact same size.
Reason (R): Iron has a higher density than wood, meaning it has more mass packed into the same unit volume.
Reason (R): Iron has a higher density than wood, meaning it has more mass packed into the same unit volume.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Density is mass per unit volume. Because iron is denser, an equal volume of iron contains much more mass than wood.
7
Assertion (A): A heavy wooden log floats on water while a tiny iron nail sinks to the bottom.
Reason (R): Whether an object floats or sinks depends on its density compared to the liquid, not its total mass or size.
Reason (R): Whether an object floats or sinks depends on its density compared to the liquid, not its total mass or size.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Wood has a lower density than water, so it floats regardless of how large the log is. Iron has a higher density, so even a small nail will sink.
8
Assertion (A): While measuring water in a measuring cylinder, one should read the mark that coincides with the top of the curved surface.
Reason (R): The curved surface of a liquid inside a narrow cylinder is called a meniscus.
Reason (R): The curved surface of a liquid inside a narrow cylinder is called a meniscus.
Answer: (d)
A is false, but R is true. For water and other colourless liquids, you must read the mark that coincides with the BOTTOM of the meniscus to get an accurate volume measurement.
9
Assertion (A): A hot air balloon rises upwards in the sky.
Reason (R): Heating the air increases its volume, which decreases its density and makes it lighter than the surrounding cool air.
Reason (R): Heating the air increases its volume, which decreases its density and makes it lighter than the surrounding cool air.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. When the air inside the balloon is heated, the particles spread out. This lowers the density of the hot air, causing the balloon to rise.
10
Assertion (A): Applying high pressure to a gas significantly increases its density.
Reason (R): Increasing pressure on gases causes their particles to move closer together, decreasing the volume.
Reason (R): Increasing pressure on gases causes their particles to move closer together, decreasing the volume.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Because gases are highly compressible, pressure forces the same amount of mass into a smaller volume, thereby increasing the density.
11
Assertion (A): Most digital weighing balances used by shopkeepers show the true weight of an object in newtons (N).
Reason (R): Mass is the quantity of matter present in an object, typically measured in grams (g) or kilograms (kg).
Reason (R): Mass is the quantity of matter present in an object, typically measured in grams (g) or kilograms (kg).
Answer: (d)
A is false, but R is true. While balances mechanically react to weight (force), they are calibrated to display the measurement in units of mass (grams or kilograms), not newtons.
12
Assertion (A): Ice floats on the surface of liquid water.
Reason (R): As water freezes into ice, its particles arrange themselves to take up less space, increasing its overall density.
Reason (R): As water freezes into ice, its particles arrange themselves to take up less space, increasing its overall density.
Answer: (c)
A is true, but R is false. Ice floats because it is LESS dense than liquid water. When water freezes, its molecular structure actually expands to take up MORE space, causing its density to drop.
13
Assertion (A): The volume of an irregular solid like a stone can be determined by measuring the amount of water it displaces.
Reason (R): The rise in the water level in a measuring cylinder is exactly equal to the volume of the object submerged in it.
Reason (R): The rise in the water level in a measuring cylinder is exactly equal to the volume of the object submerged in it.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. This is the displacement method. An immersed object displaces a volume of liquid perfectly equal to its own volume.
14
Assertion (A): In thick sugar syrup (Chashni) used for sweets, sugar is considered the solvent and water is the solute.
Reason (R): When mixing a solid and a liquid to form a solution, the liquid component is generally termed the solvent.
Reason (R): When mixing a solid and a liquid to form a solution, the liquid component is generally termed the solvent.
Answer: (d)
A is false, but R is true. Even if there is a massive amount of solid sugar dissolved in a very small amount of liquid water, the water remains the solvent and the sugar is the solute.
15
Assertion (A): The innermost core of the Earth has the lowest density compared to its outer layers.
Reason (R): As one moves deeper into the Earth, both pressure and temperature rise significantly.
Reason (R): As one moves deeper into the Earth, both pressure and temperature rise significantly.
Answer: (d)
A is false, but R is true. The inner core has the HIGHEST density. The immense pressure deep within the Earth compresses the materials, making them much heavier and more compact than the crust.
❓ Frequently Asked Questions
What is covered in CBSE Class 8 Science Chapter 9 The Amazing World of Solutes, Solvents, and Solutions?
This chapter covers all key topics from The Amazing World of Solutes, Solvents, and Solutions as per CBSE 2026-27 syllabus.
Is this Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 8 board exam preparation covering the complete syllabus.
Are these CBSE Class 8 Science Assertion & Reason updated for 2026-27?
Yes, all content at eBookPublisher is updated as per the latest 2026-27 CBSE syllabus.
How many chapters are in CBSE Class 8 Science?
All chapters of CBSE Class 8 Science are covered at eBookPublisher with free Assertion & Reason for each chapter.
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