Yeah that’s when I ask for the check please :)
I just read a little about it. Somehow frozen molecules, if they have enough energy, will evaporate even at 0 degrees celsius.
That’s where I stopped reading :)
I’m with you - when even the “simple concepts”, that we know we can grasp, become incomprehensible, it’s time to let the egg-heads work it out.
I also remember furiously scratching my head when scientists asserted that even Black Holes could “evaporate” and lose mass.
Don’t get discouraged, it’s truly not that complicated. Liquids at temperatures below their boiling point will evaporate; that’s certainly a familiar concept. Solids can do the same. It’s also possible for a solid to change directly into a gas without passing through the liquid phase, again think dry ice (that’s why we call it dry ice). Why can dry ice do this but not regular ice?
The answer is pressure. Dry ice is actually solid carbon dioxide. In order to exist as a liquid, any substance needs to have a certain amount of pressure to do so. There are no liquids in a vacuum. If you try to put water, for instance, in a closed, evacuated container, the water will boil, even at room temperature. If you have enough water and a tight container, it will eventually stop boiling. That’s because the water vapor in the container will exert a pressure and allow liquid water to exist. The pressure at which this happens is called the vapor pressure, and it depends on both the temperature and the identity of the substance.
This is not limited to liquids, but also occurs for solids. The vapor pressure of most solids is very small, though, so we don’t notice solids changing to gases very often. In the case of dry ice though, the vapor pressure is higher than atmospheric pressure at all temperatures above -78C. Thus dry ice evaporated. It does not melt, though, because of another pressure, the critical pressure. The critical pressure of each substance is simply the minimum pressure needed to have a stable liquid form. For carbon dioxide the critical pressure is far above atmospheric pressure, so we don’t see liquid carbon dioxide. The liquid does exist, but pressures must be high enough. If you buy pressurized tanks of carbon dioxide for a soda fountain, those tanks actually contain liquid carbon dioxide.
When talking about phase changes, we are accustomed to thinking that changes in temperature cause them, but as discussed above, pressure can also do so. You can boil liquids by reducing pressure. You can also liquefy gases by increasing pressure. Ice skating works because water is strange - increasing pressure on the solid makes it melt. The skate blade exerts a large pressure on the ice causing a temporary layer of liquid water to form and you can glide on that water. The triple point of any substance is a condition of BOTH temperature and pressure that allows all three phases to exist at once. If you’ve seen a triple point cell, it is actually evacuated to a low pressure. Both the temperature and pressure must be maintained to keep the equilibrium. Tapping on it changes the pressure.
It only seems complex because we live our entire lives within a very narrow range of ambient pressure. Varying the pressure is the cause of all these phenomena that you find unfamiliar.