Liquids are not necessarily heavier than solids. The concept of "heaviness" is related to density, which is the mass of a substance per unit volume.

Here's the breakdown:

* Density is what determines if something sinks or floats. A denser object will sink in a less dense fluid.

* Solids tend to have higher density than liquids because their molecules are packed more tightly together.

* Liquids have more freedom of movement between their molecules compared to solids, making them less dense.

Examples:

* Water (liquid) is denser than ice (solid). This is why ice floats on water.

* Steel (solid) is denser than mercury (liquid). Steel would sink in mercury.

It's crucial to remember that density depends on the specific substance. There are many cases where a solid is less dense than a liquid.