Like heat energy changing the form of the water
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Temperature is defined as the average kinetic energy of the molecules in a substance. KE = 3/2 * k * T, KE average kinetic energy, k is the boltzmann constant, and T is temperature in Kelvin.
Molecules also generally like to stick to each other, but if they are moving fast enough, they bounce right off and can’t stick because they have too much energy. Imagine it like a ball and a valley. If you gently roll the ball into the valley, it won’t roll up and out the other side. If you throw the ball down the hill, that energy let’s it roll up and out the other side. The colder molecules get stuck in the valley, forming a solid, and the hotter molecules make it out of the valley, and form a liquid. The same type of valley happens between a gas and a liquid too.
When a molecule gets stuck in a valley, it has to give up all of that extra energy, and that extra energy is called the latent heat of fusion (when dealing with melting and freezing) and latent heat of vaporization (when dealing with boiling and condensing). When getting out of the valley, it has to absorb that same amount of energy again. E = m * h, the energy required for a phase change is the mass of the substance times the latent heat of the substance. If you boil a pot of water, while it’s boiling the water is exactly at the boiling point. That’s because all of the energy you’re pumping in that would normally increase the temperature is going into the latent heat, and temperature doesn’t change while the phase change is happening. The same applies for all phase changes.
Also, if you ever looked at a phase change diagram, if pressure is low enough, liquids can’t exist, the transition goes right between solid and gas. CO2 does this at atmospheric pressure, which is why dry ice works the way it does. At higher pressures, liquid CO2 can exist. At extremely high pressures, the line between liquid and gas is blurred, and its just called a supercritical fluid. Both of these situations are basically the two valleys overlapping.
Fun fact: at a specific temperature and pressure (depending on the material) called the triple point, all 3 traditional phases of matter can exist at the same time.
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