Molecules move differently depending on whether they are in a liquid, gas, or solid phase. Molecules in a solid cannot change position very easily. Instead, they stay in one place and vibrate. Molecules in a liquid can move around quite easily. They can change position and slide past each other. Molecules in a gas move around very easily. In a gas, the molecules spread out evenly to fill the container they are in. Imagine you are in a big crowd of people. Someone on the loud speaker asks everyone to join hands with whoever is closest by, so everyone in the whole crowd gets close together and joins hands, every which way. When everyone is holding hands, would you be able to move to the other side of the room without letting go of a hand? No, you would only be able to shift around a little bit right where you are. This is similar to the molecules in a solid, tightly packed.
Now imagine in the same crowd you are told to hold onto the end of 3 foot sections of rope. You are given a little bit more room to move so as a crowd you can change your shape. This would be similar to the molecules in a liquid.
If you were told to stay in the room, but not connected at all to each other, you would be moving similar to the molecules in a gas. You would not have a definite shape.
Molecules
What phase of matter has molecules that are packed the closest together?
The molecules in a solid are packed the closes together.
