Eli5 – Sublimation


How can a cold solid turn into a gas? Skipping the liquid part?

In: 5

Liquids need a certain temperature and pressure range to exist. A good example is carbon dioxide (dry ice, when it’s solid), which needs more than five times atmospheric pressure to be a liquid at any temperature. Therefore, if the temperature is high enough, its phase will change from solid to vapor (or vice versa). Sublimation can also happen during solid-vapor equilibrium.

It’s a wonder that liquids can exist at all.

A gas exists when the molecules have so much energy that they aren’t sticking together, and instead freely bouncing around.

A solid exists when they have so little energy that they settle together into a dense array.

Liquids are in a strange in-between, where the molecules still mostly clump together but can’t quite settle down. This is only possible because of pressure. In low pressures, liquids turn to gas. If the pressure isn’t high enough for a particular material to exist as a liquid, then it skips that and becomes a gas.

A great example of sublimation in nature is in Canada or anywhere that has freezing temperatures. After snow covers everything and becomes solid ice on the roads and sidewalks, we’ll have a -40°C day where it’s nothing but pure sunshine and the sidewalks and roads experience sublimation from the uv lights and it clears up the roads and sidewalks even though it’s way too cold for water to form. Idk if that’s what you’re looking for but the other posts described the actual science behind it so I’m providing an example, if that makes sense