Chapter Exercises Solutions

Questions and Answers

1. True/False

(i) Oxygen is more soluble in hot water. (False) - Gas solubility decreases with heat. (ii) Sand and water is a solution. (False) - It is a non-uniform mixture (Suspension). (iii) Space occupied is mass. (False) - Space is Volume. (iv) Unsaturated has more solute than saturated. (False) - Saturated has the maximum possible. (v) Mixture of gases is a solution. (True) - Air is a gaseous solution.

2. Fill in the Blanks

(i) immersed/dipped; rise/increase. (ii) solute; solvent (or solution). (iii) decreases. (Heating expands volume, Mass stays same, so $D=M/V$ decreases). (iv) saturated.

3. Oil on Water

Answer: (i) Oil is lighter (less dense) than water. Note: The question asks “Oil floats… what does this tell you?”. Usually implies lesser density. However, technically “Lighter” is a vague term, “Less Dense” is scientific. Checking options: (i) Oil is denser (False), (ii) Water is denser (True), (iii) Same density (False), (iv) Dissolves (False). Correct Selection: (ii) Water is denser than oil (or Oil is less dense than water).

4. Stone Density

• Mass ($m$) = 225 g
• Volume ($V$) = 90 cm³
• Density = $225 / 90 = 2.5 \text{ g/cm}^3$.
• Prediction: Water density is $1 \text{ g/cm}^3$. Since $2.5 > 1$, the stone will sink.

5. Saturated Solution Statement

Answer: (iii) No more solute can be dissolved into the saturated solution at that temperature. (This is the definition).

6. Bottle Capacity

• Total Capacity = 2 Litres = 2000 mL.
• Filled = 500 mL.
• More needed = $2000 - 500 = 1500 \text{ mL}$ (or 1.5 Litres).

7. Calculate Density

• $m$ = 400 g
• $V$ = 40 cm³
• Density = $400 / 40 = 10 \text{ g/cm}^3$.

8. Orange Float/Sink (Fig 9.25)

• Unpeeled Orange: Floats. The peel contains porous air pockets, lowering the overall density of the orange to less than water.
• Peeled Orange: Sinks. Without the airy peel, the dense fruit flesh is denser than water.

9. Which is Denser?

• Object A: $D = 200 / 40 = 5 \text{ g/cm}^3$.
• Object B: $D = 240 / 60 = 4 \text{ g/cm}^3$.
• Answer: Object A is denser.

10. Clay Modeling

Answer: Density will remain the same.

• Density is an intrinsic property of the material. Changing shape (cube to sheet) does not change the Mass or the Volume of the material itself.

11. Iron Block Volume

• Mass = 600 g
• Density = 7.9 g/cm³
• Formula: $V = m / D$
• $V = 600 / 7.9 \approx 75.95 \text{ cm}^3$.

12. Hot Water Experiment (Fig 9.26)

• Observation: Water level rises in the tube when placed in hot water.
• Reason: Heat causes water to expand (Volume increases).
• Effect on Density: Since Mass is constant and Volume increases, Density decreases.