how come spilled water inside and outside evaporates so quickly despite water’s evaporation point bring 100°, no where near the ambient temperature in home or outside?
In: 365
Water’s *boiling* point is 100 Celsius, but individual water molecules can at times get enough energy to reach the equivalent of 100 C and evaporate by themselves.
The latent heat of vaporization is the amount of energy needed in a substance to change phases from a liquid to a gas. At 100° Celsius temperature and one atmosphere of pressure, there is enough energy that this change is pretty much immediate. At lower temperatures, however, there can still be enough energy to cause some of the substance to change from liquid to gas. At higher temperatures and lower pressures, the likelihood of this phase change increases, which is why water at 2° C tends to take longer to evaporate than water at 50° C, which takes even longer than water at 100° C.
Note: all of this is only partially correct! Physics is very very complicated, but I won’t go down every rabbit hole in a ELI5. (this is more like ELI15 anyways)
The boiling point of water is 100°C, not the evaporation point (there is no such thing). Every liquid evaporates all the time until its “[partial pressure](https://en.wikipedia.org/wiki/Partial_pressure)” is reached in the air around it. In a big room or outside, the partial pressure of water never reaches the maximum. The partial pressure of water in the air is often referred to as humidity.
The temperature of a substance is the *average* speed of the molecules. This means in any substance, there are quicker and slower molecules. In solids that doesn’t matter much, because even the quickest (hottest) particles don’t have enough energy to escape their neighbours. Solids are held together very strongly.
That is different for liquids. In a liquid the molecules are held together very weakly, which is why they can flow and change their shape easily. Single molecules in a liquid can gain enough speed overcome the attractive forces of its medium and “fly away” from the rest and become a gas in the surrounding air. This process of single molecules leaving the liquid and becoming gas is called evaporation.
If the temperature of a liquid reaches the point where the *average* speed of molecules is high enough to escape, we call this boiling temperature of that liquid (100°C for water). You may ask, why not every molecule evaporates instantly, once the liquid reaches its boiling point. The answer is simple: Even in a boiling liquid, only the *average* speed is high enough to escape and every time a molecule escapes, the liquid “cools down” a tiny tiny bit, because it just lost its quickest (read: hottest) molecule, therefore being under its boiling point on average again. This is also why you can’t heat a liquid over its boiling temperature. The temperature doesn’t rise because more and more quick particles escape and therefore bring down the average speed in the liquid.
Be aware: the boiling point is dependent on the ambient pressure. 100°C is only the correct boiling point for water at sea level so 1 bar of pressure. This is why a pressure cooker cooks quicker: the pressure is higher, therefore the boiling point of water is higher, so the water gets hotter than its “normal” boiling point would allow it to get. Higher temperature means quicker cooking. Fun fact: everything cooks really really really slowly, even in the fridge or freezer. The point is, things go bad way quicker at these temperature than they cook themselves.
BTW: as the quickest molecules leave the liquid first, its overall temperature drops, making it harder for more molecules to escape. This is one of the methods hot liquid (like tee or coffee) cool down by (the other ones being heat transfer to the cup and infrared radiation). You can often see this in a very dry room (for example in winter) as little bit of water vapor over the no longer boiling coffee.
Water particles are moving around quickly even when water is liquid and below 100°C.
Some particles get fast enough to escape into the air.
This happens until all water particles are in the air under normal circumstances.
Waters vapor pressure, which is the amount of vapor-phase water that will exist above liquid water, is why this happens. Even Ice had some vapor pressure and will evaporate. At room temperature, water has a vapor pressure of around 0.03 atmospheres, which means you can get roughly 3% water in ambient air at 100% humidity. If you’re below that, the water will evaporate until the humidity reaches 100%. The rate at which it evaporates is based on a difference between water’s vapor pressure and the humidity level in the air. This is why you feel hot/sticky on humid days: your sweat can no longer evaporate as quickly, so your body has trouble cooling off, and your sweat just sticks on you.
At higher temperatures, water has a higher vapor pressure. 100C is the point at which the vapor pressure is exactly 1 atmosphere, which means you can have 100% water in the vapor phase at ambient pressures. This means that the water will boil far more vigorously – if you’re boiling in an open container, the vapor phase above the water will never hit 100% water.
In a closed container, it will boil briefly and then stop once the pressure rises and the vapor-phase water concentration increases.
As others have stated, 100C is the boiling point, not evaporation which is a different process.
With boiling, you’re actively turning the water from a liquid to a gas which can then fly away.
With evaporation, you have to zoom in to the atoms to see what’s going on. All atoms have some amount of kinetic energy. Their wizzing around, bumping into other atoms, vibrating, rotating, etc. Sometimes, right at the surface of water, one of these wizzing atoms just sort of **pops** right off the rest of the water and keeps wizzing away. That’s evaporation. It’s when atoms have just enough energy to individually escape the rest of their pack without changing their state of matter.
Many of these explanations are certainly not ELI5. Why have a sub Refdit called ELI5 when people who are highly educated do not like the simplistic answers. Granted the simple answers may sound incomplete, or even incorrect to the highly educated. However, unless an explanation is way off base, then allow the people who try to communicate with the ELI5 readers to be less than perfect in their answers. Consider this, if you do not know much about why inflation or recession occur do you want a Harvard economics professor to explain it to you, or do you want a 5th grade teacher who minored in economics to explain it to you?
Oversimplified but this ELI5, commonly we have three conditions of matter, from highest density, solid, liquid, and air. If sugar is soluble in water (solid to liquid), then water also soluble in air (liquid to air).
The real key is the difference between evaporation and vaporization. Evaporation (mostly) happens at the surface of a liquid whereas vaporization (boiling) happens within the liquid. The difference is in the energy of those molecules. All water molecules are attracted to other water molecules because water molecules are like little magnets. All the molecules within the liquid have molecules surrounding them holding them in place, meaning it takes a lot of energy to get them to boil. Molecules on the surface have air above rather than more water, so they have less molecules to escape from and need less energy to escape to a gaseous state, so it can happen at much lower temperatures.
Because water doesn’t have to boil to evaporate.
Water can evaporate at any temperature. In ELI5 terms, think of a glass of water as a whole bunch of tiny molecules stuck together. When they heat up, they vibrate, and eventually vibrate enough to ‘unstick’ from each other until a single water molecule will break free of the surface and float away into the air.
So, boiling water is just adding a lot of heat to the water which will make those bonds break faster and more violently, so the water will evaporate faster.
This is also why blowing on water will help it evaporate faster, the air molecules collide with the water molecules, transfer their energy to them and help them break free.
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