Class 8 Science Chapter 9 The Amazing World of Solutes Solvents and Solutions Solutions

🌟 Class 8 Science – Curiosity Chapter 9

🧪 The Amazing World of Solutes, Solvents & Solutions

🟢 1. State whether the statements given below are True [T] or False [F]. Correct the false statement(s).

(i) Oxygen gas is more soluble in hot water rather than in cold water.

(ii) A mixture of sand and water is a solution.

(iii) The amount of space occupied by any object is called its mass.

(iv) An unsaturated solution has more solute dissolved than a saturated solution.

(v) The mixture of different gases in the atmosphere is also a solution.

✅ Answer:

(i) ❌ [F] False

✔️ Correct: Oxygen gas is more soluble in cold water (ठंडे पानी)

📌 Reason: Temperature ↑ → Gas solubility ↓

(ii) ❌ [F] False

✔️ Correct: Sand + water = non-uniform mixture (suspension)

👉 Solution = uniform mixture (समांग मिश्रण)

(iii) ❌ [F] False

✔️ Correct: Space occupied = Volume (आयतन)

👉 Mass = amount of matter

(iv) ❌ [F] False

✔️ Correct: Saturated solution has maximum solute

👉 Unsaturated solution can dissolve more

(v) ✅ [T] True

🌬️ Air = gaseous solution

👉 Nitrogen = solvent, others = solutes

🟢 2. Fill in the blanks.

(i) The volume of a solid can be measured by the method of displacement, where the solid is ______ in water and the ______ in water level is measured.

(ii) The maximum amount of ______ dissolved in ______ at a particular temperature is called solubility at that temperature.

(iii) Generally, the density ______ with increase in temperature.

(iv) The solution in which glucose has completely dissolved in water, and no more glucose can dissolve at a given temperature, is called a ______ solution of glucose.

✅ Answer:

(i) 👉 immersed, rise 💧

(ii) 👉 solute, solvent 🧪

(iii) 👉 decreases 🌡️⬇️

(iv) 👉 saturated ✔️

🟢 3. You pour oil into a glass containing some water. The oil floats on top. What does this tell you?

(i) Oil is denser than water

(ii) Water is denser than oil

(iii) Oil and water have the same density

(iv) Oil dissolves in water

✅ Answer:

👉 Correct option: (ii) Water is denser than oil

🧠 Explanation:

👉 Less dense liquid floats ⬆️

👉 Oil floats → Water more dense 💧

🟢 4. A stone sculpture weighs 225 g and has a volume of 90 cm³. Calculate its density and predict whether it will float or sink in water.

✅ Answer:

📌 Formula:

👉 Density = 225 / 90 = 2.5 g/cm³

📊 Comparison:

Water = 1 g/cm³
Object = 2.5 g/cm³

👉 It will sink (डूबेगा) ⬇️

🟢 5. Which one of the following is the most appropriate statement and why are the other statements not appropriate?

(i) A saturated solution can still dissolve more solute at a given temperature.

(ii) An unsaturated solution has dissolved the maximum amount of solute possible at a given temperature.

(iii) No more solute can be dissolved into the saturated solution at that temperature.

(iv) A saturated solution forms only at high temperatures.

✅ Answer:

👉 Correct: (iii) ✔️

❌ (i) → Unsaturated solution

❌ (ii) → Definition wrong

❌ (iv) → Any temperature pe possible

🟢 6. You have a bottle with a volume of 2 litres. You pour 500 mL of water into it. How much more water can the bottle hold?

✅ Answer:

📌 2 L = 2000 mL

👉 Remaining = 2000 – 500 = 1500 mL

💧 Final: Bottle can hold 1500 mL (1.5 L) more

🟢 7. An object has a mass of 400 g and a volume of 40 cm³. What is its density?

✅ Answer:

📌 Formula:

👉 Density = 400 / 40 = 10 g/cm³

🟢 8. Analyse Fig. 9.25a and 9.25b. Why does the unpeeled orange float, while the peeled one sinks? Explain.

✅ Answer:

🍊 Unpeeled Orange:

Air pockets present 🌬️
Density ↓ → floats ⬆️

🍊 Peeled Orange:

No air spaces
Density ↑ → sinks ⬇️

📌 Conclusion:

👉 Floating depends on density (घनत्व)

🟢 Question 9 and 10 of Class 8 Science Curiosity Chapter 9

🟢 9. Object A has a mass of 200 g and a volume of 40 cm³. Object B has a mass of 240 g and a volume of 60 cm³. Which object is denser?

✅ Answer:

📌 Formula:

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🧮 Object A:

👉 Density = 200 / 40 = 5 g/cm³

🧮 Object B:

👉 Density = 240 / 60 = 4 g/cm³

📊 Comparison:

🔴 Object A = 5 g/cm³

🔵 Object B = 4 g/cm³

👉 Object A is denser (अधिक घनत्व वाला) ✔️

🟢 10. Reema has a piece of modeling clay that weighs 120 g. She first moulds it into a compact cube that has a volume of 60 cm³. Later, she flattens it into a thin sheet. Predict what will happen to its density.

✅ Answer:

📌 Formula:

👉 Density = 120 / 60 = 2 g/cm³

🧠 Concept:

🔄 Shape changes (आकार बदलता है)

❌ Mass same (द्रव्यमान समान)

❌ Volume same (आयतन समान)

👉 Density remains SAME ✔️

📌 Conclusion:

👉 Density is an intrinsic property (स्वाभाविक गुण)

👉 Shape change does NOT affect density

🟢 Class 8 Science Curiosity Chapter 9 Question 11 and 12

🟢 11. A block of iron has a mass of 600 g and a density of 7.9 g/cm³. What is its volume?

✅ Answer:

📌 Formula:

👉 Volume = 600 / 7.9 ≈ 75.95 cm³

📌 Final Answer:

👉 Volume ≈ 75.95 cm³ ✔️

🟢 12. You are provided with an experimental setup as shown in Fig. 9.26a and 9.26b. On keeping the test tube (Fig 9.26b) in a beaker containing hot water (~70°C), the water level in the glass tube rises. How does it affect the density?

✅ Answer:

🌡️ When water is heated:

Particles gain energy ⚡
Move faster 🏃
Spread apart ↔️

👉 Volume increases (आयतन बढ़ता है)

👉 Water level rises in tube 📈

🧠 Analysis:

❌ Mass = same

✔️ Volume = increases

👉 Density decreases (घटती है) ⬇️

📌 Conclusion:

👉 Heating → Volume ↑ → Density ↓

Class 8 Science Chapter 9 The Amazing World of Solutes Solvents and Solutions Solutions | Curiosity NCERT Answers

Amresh Academy

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