Why is the “melting point” and “freezing point” of water the same temperature (0° Celsius)?
Is this always true with any material?
Compare the heat energy in a teaspoon of boiling water and a swimming pool full of room temperature water.
The melting point and freezing point of water is the same temperature (0° Celsius) because it is a unique characteristic of water. This is due to the hydrogen bonds formed between water molecules. When water freezes, the hydrogen bonds arrange into a hexagonal lattice structure, resulting in the expansion of water molecules and a decrease in density. This expansion and increase in space between molecules causes ice to be less dense than liquid water. On the other hand, when water is heated and reaches its melting point, the hydrogen bonds are broken, and the water molecules become more chaotic and move more freely, transitioning from a solid to a liquid state.
This phenomenon is not always true with any material. Different substances have different melting and freezing points, depending on their molecular structure and intermolecular forces.
Comparing the heat energy in a teaspoon of boiling water and a swimming pool full of room temperature water is not a straightforward comparison. The swimming pool contains a significantly larger volume of water, which requires a greater amount of heat energy to raise the temperature. However, the boiling water in a teaspoon is at a much higher temperature compared to room temperature water in the swimming pool. The heat energy depends on the mass and temperature of the water, therefore, the total heat energy in the teaspoon of boiling water may still be less than that in the swimming pool full of room temperature water due to the large volume difference.