The Amazing World of Solutes, Solvents, and Solutions

(i) False [F]
Correction: Oxygen gas is *less* soluble in hot water than in cold water. Generally, the solubility of gases *decreases* with an increase in temperature.

(ii) False [F]
Correction: A mixture of sand and water is *not* a solution. It is a heterogeneous (non-uniform) mixture because sand does not dissolve in water and the particles are visible and settle down.

(iii) False [F]
Correction: The amount of space occupied by any object is called its *volume*, not mass. Mass is the amount of matter present in an object.

(iv) False [F]
Correction: A *saturated* solution has the maximum amount of solute dissolved at a given temperature. An unsaturated solution has *less* solute dissolved than a saturated solution (i.e., more solute can still be dissolved in it).

(v) True [T]
The atmosphere is a uniform mixture of different gases such as nitrogen, oxygen, carbon dioxide, argon, etc., so it qualifies as a solution (gaseous solution).

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

(ii) The maximum amount of solute dissolved in a fixed quantity of solvent (or solution) at a particular temperature is called solubility at that temperature.

(iii) Generally, the density decreases 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 saturated solution of glucose.

Correct Answer: (ii) Water is denser than oil

Justification: When two immiscible liquids are mixed, the denser liquid sinks to the bottom and the less dense liquid floats on top. Since oil floats on water, it means oil is less dense than water, i.e., water is denser than oil. The density of water is approximately $1\ \text{g/cm}^3$ while the density of oil is approximately $0.8{-}0.9\ \text{g/cm}^3$.

Given:
- Mass of stone sculpture $= 225\ \text{g}$
- Volume of stone sculpture $= 90\ \text{cm}^3$

Formula:
$$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$$

Calculation:
$$\text{Density} = \frac{225\ \text{g}}{90\ \text{cm}^3} = 2.5\ \text{g/cm}^3$$

Prediction:
The density of water is $1\ \text{g/cm}^3$. Since the density of the stone sculpture ($2.5\ \text{g/cm}^3$) is greater than the density of water ($1\ \text{g/cm}^3$), the stone sculpture will sink in water.

Answer: Density $= 2.5\ \text{g/cm}^3$; the sculpture will sink in water.

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

Explanation:
A saturated solution is defined as the solution in which the maximum amount of solute has already been dissolved at a given temperature, and no more solute can be dissolved in it at that temperature. Statement (iii) correctly captures this definition.

Why the other statements are not appropriate:

- (i) is incorrect: A saturated solution has already reached its maximum capacity of dissolving solute. It *cannot* dissolve any more solute at the same temperature. This is the opposite of what a saturated solution means.

- (ii) is incorrect: It is the *saturated* solution (not the unsaturated solution) that has dissolved the maximum amount of solute possible at a given temperature. An unsaturated solution still has the capacity to dissolve more solute.

- (iv) is incorrect: A saturated solution can form at *any* temperature, not just at high temperatures. The amount of solute that saturates a solution may differ with temperature, but saturation is not restricted to high temperatures only.

Given:
- Total volume of the bottle $= 2\ \text{litres} = 2000\ \text{mL}$
- Volume of water already poured $= 500\ \text{mL}$

Calculation:
$$\text{Remaining capacity} = \text{Total volume} - \text{Volume already filled}$$
$$\text{Remaining capacity} = 2000\ \text{mL} - 500\ \text{mL} = 1500\ \text{mL}$$

Answer: The bottle can hold 1500 mL (or 1.5 litres) more water.