The quantity which changes with temperature

The correct option is Molarity.

To understand why molarity changes with temperature while the other options do not, let us analyze the definitions of each concentration term:

1. Molarity is defined as the number of moles of solute dissolved per liter of solution:
$\text{Molarity}=\frac{\text{Moles of solute}}{\text{Volume of solution (in Liters)}}$
Because volume is directly proportional to temperature (as temperature increases, liquids expand, causing the volume of the solution to increase), molarity depends on temperature. Specifically, as temperature increases, the volume of the solution increases, which in turn decreases the molarity.

2. Molality is defined as the number of moles of solute per kilogram of solvent:
$\text{Molality}=\frac{\text{Moles of solute}}{\text{Mass of solvent (in kg)}}$
Mass is a quantity that does not change with temperature. Therefore, molality is independent of temperature.

3. Mole fraction is the ratio of the number of moles of a particular component to the total number of moles in the mixture:
${\chi }_A=\frac{n_A}{n_A+n_B}$
Since the number of moles is calculated from mass (which is temperature-independent), the mole fraction does not change with temperature.

4. Mass percentage is defined as the mass of solute per unit mass of solution, multiplied by 100:
$\text{Mass percentage}=\frac{\text{Mass of solute}}{\text{Total mass of solution}}\times 100$
Since it is based entirely on mass measurements, it is completely independent of temperature.

In conclusion, concentration terms that involve volume (like Molarity) change with temperature, whereas those that are based strictly on mass (like Molality, Mole fraction, and Mass percentage) remain unaffected by temperature variations.