Why is hot water heavier than cold water?

Hot water is heavier than cold water because of the difference in molecular structure between the two. Hot water molecules are more spread out than cold water molecules, making them less dense and thus lighter. This is because when water is heated, the molecules move faster and farther apart, creating more space between them and making the overall density of the water less. Cold water molecules, on the other hand, are more tightly packed together, making them denser and thus heavier. This is because when water is cooled, the molecules slow down and move closer together, reducing the amount of space between them and making the overall density of the water higher.

The difference in molecular structure between hot and cold water is due to the fact that heat energy causes the molecules to vibrate and move around more quickly, which in turn causes them to spread out. This is why hot water is less dense and lighter than cold water.