The three states of Matter are solids, liquids, and gases. This will cover how the molecules will look like when they are in these different forms.
The molecules in solids are very solid. They barely have room to move! Imagine a cluster of balls in a box squished together. The molecules are close to each other giving it a definite size and shape.
The molecules in a liquid are free-flowing. They are not bunched up, nor too far apart. It has a definite size but no definite shape.
Gases have molecules that are all over the place. The are very spread out, just like children on a large playground. Gases can move through small gaps and large holes! They are have no size or shape!