Final answer:
The difference between capillary melting point and true melting point is that the true melting point is an intrinsic property of a substance, while the capillary melting point may vary due to impurities, pressure, and other experimental conditions.
Step-by-step explanation:
The capillary melting point and the true melting point refer to two different ways of determining the melting point of a substance. The true melting point is the temperature at which a solid becomes a liquid at atmospheric pressure. In contrast, the capillary melting point is a method typically used in laboratories where the substance is sealed in a thin capillary tube and observed under a microscope as it is heated. Differences can arise between these two measurements due to impurities, pressure variations, or experimental conditions.
While the true melting point is an intrinsic property of a substance determined by intermolecular forces and is not affected by external conditions, the capillary melting point can sometimes deviate from the true melting point. This deviation often happens if the sample being used is impure or if there are variations in atmospheric pressure. Notably, for water (H₂O), we know that its true melting point is 0°C at 1.00 atm, where both solid and liquid water can exist in equilibrium.