Hot water is not inherently heavier than cold water. In fact, the density of water decreases as it is heated, which means that hot water is typically less dense than cold water. This property is due to the unusual behavior of water's density in relation to its temperature.
Water reaches its maximum density at approximately 4 degrees Celsius (39.2 degrees Fahrenheit). As the temperature of water decreases below 4 degrees Celsius, its density begins to decrease. This is why ice, which is formed from water at lower temperatures, floats on top of liquid water.
When water is heated above 4 degrees Celsius, it expands and becomes less dense. This is because the heat energy causes the water molecules to move more vigorously, increasing the average distance between them. As a result, hot water is less dense and will tend to rise when mixed with colder water.
However, it is worth noting that other factors can affect the density of water, such as the presence of dissolved substances or impurities. For example, if hot water contains dissolved salts or minerals, it may have a higher density than pure cold water due to the increased solute concentration. But in general, the temperature alone does not determine whether hot water is heavier or lighter than cold water.