Here's why:

* Solids have molecules that are tightly packed together. This allows sound vibrations to travel quickly from one molecule to the next.

* Liquids have molecules that are more loosely packed, so sound travels slower.

* Gases have the most widely spaced molecules, making sound travel the slowest.

Think of it like this: Imagine a line of people holding hands. If you shake the hand of the person at the beginning of the line, the vibration will travel quickly down the line because the people are close together. This is similar to how sound travels through a solid.