Video: Recalling the State of Matter for Which Particles Have the Most Energy

A substance can exist as a solid, liquid, or gas. In which of the states of matter do particles in the substance have the most energy?

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Video Transcript

A substance can exist as a solid, liquid, or gas. In which of the states of matter do particles in the substance have the most energy?

One great example of a substance that can exist as a solid, a liquid, or a gas is water. We know that water can exist as a chunk of ice, that is, a solid. Or it can exist as a liquid, just water. Or it can exist as water vapour, a gas. What we want to know is in which of these states of matter, solid, liquid, or gas, do the particles in our substance have the most energy.

To figure that out, we can consider just how it is that water moves from being a solid to being a liquid to being a gas. For example, considering the transition from solid to liquid, we know that if we leave an ice cube out on a counter, eventually it will melt. It will become a liquid. That happens because heat from the environment is added to the ice cube. If we wanted to, we could speed up this process by putting the ice cube in a dish and heating the dish. This shows us that, in order to go from a solid to a liquid, we need to add energy to our substance.

And the same is true in going from a liquid to a gas. If we heat up water in a pan, then eventually, the water will start to boil. That is, it will vaporize. Just like before, we’re adding energy into our substance, which is changing its state now from a liquid to a gas. From this perspective, we would guess that the particles in the gaseous state of our substance have the most energy.

Another way to see this is to think of it in terms of the average speed of the particles in each state of matter. When our substance is a solid, the particles in it are arranged in a very orderly fashion. They don’t move quickly at all. But then, as we add energy to our substance, the average speed of the particles picks up. The average particle speed in a liquid is higher than that in a solid. And higher still as we might be able to see from the sketch is the average speed of the particles in a gas compared to that in a liquid.

Both of these perspectives indicate the same answer to this question. They both tell us that the state of matter in which a material has the most energy is the gaseous state.

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