Energy of Solids, Liquids, and Gases

Most recent answer: 10/22/2007

What is the energy state of solid,gas and liquid?
- Brian (age 10)
Brian -

I don’t quite understand what you mean by "energy states," but here’s what I do know about solids, liquids, and gases. Solids are things where the molecules are all stuck together very tightly in a regular pattern. The molecules move around very little and have a low amount of energy. If you add energy by heating it up, the molecules will move around faster and slide against each other, and it will be a liquid. Molecules in a liquid have more energy than molecules in a solid. And if you heat it up even more, the molecules will speed up so much that they won’t be stuck together at all. The molecules in the gas have the most energy.


(published on 10/22/2007)

Follow-Up #1: energy in solids, liquids, and gases

how is the amount of energy different in solids, liquids and gases I value your opinion
- kayla (age 12)
canton , ohio, america
It's pretty close to what Tamara wrote. If you take some cold solid material and add energy to it (heat it up) the particles in it will rattle around more. Usually at some point they will rattle so much that they break up the regular solid pattern and start sliding around as a liquid. (I'm assuming here that everything is done at some fixed pressure.) Then as you add more energy the individual particles break loose from the liquid and go flying around separately- a gas. (In some materials the solid goes directly to the gas without going through a liquid state.) So the energy per particle is biggest for the gas and smallest for the solid.

In one case (3He) you can actually make the liquid turn solid by heating it up. In that weird case the solid has more energy than the liquid. The reasons for that special behavior are too tricky for me to describe here. It's something you may get to understand if you study physics further.

Mike W.

(published on 01/05/2012)

Follow-Up #2: turning gas to liquid

What happens when you take energy out of a gas? Will it become a liquid?
- Cassandra (age 13)

Yes, that's exactly how it works. There are some exceptions (for example, CO2) for which the gas turns directly to a solid when it's cooled down.

Mike W.

(published on 11/22/2015)