Steam is formed at 100°C but I see “steam” being produced at less than that temperature. What is that and why isn’t it steam?
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At pretty much any temperature, there’s some amount of water converting into water vapor. Behold: [edit: grabbed the wrong visual the first time; let’s try this.]
[https://en.wikipedia.org/wiki/Vapour_pressure_of_water](https://www.engineeringtoolbox.com/docs/documents/599/Water_saturation_pressure_C.jpg)
The amount of the water that converts into vapor goes from “miniscule” at cold temperatures, to “a fair bit” at warm temperatures, “quite a bit” at 80-90C, to “100%, just give it a minute” at 100C.
In other words, the equilibrium favors liquid as long as you’re below 100C, but once you cross 100 degrees the equilibrium shifts to favoring gas. The energies of the particles are distributed in a bell curve (I forget if it’s normally distributed, but that’s the general shape) so in cold water we have “only the top 0.1% are energetic enough to vaporize” and that number increases until somewhere above 100 degrees we’re at “only the lowest 0.1% would have low enough energy to condense”.
I’m fairly sure the wisps we see above hot water are actually condensed water droplets, like a cloud. So yes, that region is rich in H2O gas, but what you’re seeing isn’t the gas, it’s tiny bits of liquid being carried upward because they’re suspended in a plume of hot gas.
At pretty much any temperature, there’s some amount of water converting into water vapor. Behold: [edit: grabbed the wrong visual the first time; let’s try this.]
[https://en.wikipedia.org/wiki/Vapour_pressure_of_water](https://www.engineeringtoolbox.com/docs/documents/599/Water_saturation_pressure_C.jpg)
The amount of the water that converts into vapor goes from “miniscule” at cold temperatures, to “a fair bit” at warm temperatures, “quite a bit” at 80-90C, to “100%, just give it a minute” at 100C.
In other words, the equilibrium favors liquid as long as you’re below 100C, but once you cross 100 degrees the equilibrium shifts to favoring gas. The energies of the particles are distributed in a bell curve (I forget if it’s normally distributed, but that’s the general shape) so in cold water we have “only the top 0.1% are energetic enough to vaporize” and that number increases until somewhere above 100 degrees we’re at “only the lowest 0.1% would have low enough energy to condense”.
I’m fairly sure the wisps we see above hot water are actually condensed water droplets, like a cloud. So yes, that region is rich in H2O gas, but what you’re seeing isn’t the gas, it’s tiny bits of liquid being carried upward because they’re suspended in a plume of hot gas.
water vapor forms at all temperatures, not just at 100°c. Water vapor even forms below freezing, that’s why ice cubes in your freezer will shrink over time in a process called sublimation. 100°c is just the temperature at which water instantly turns into vapor at sea level.
water vapor forms at all temperatures, not just at 100°c. Water vapor even forms below freezing, that’s why ice cubes in your freezer will shrink over time in a process called sublimation. 100°c is just the temperature at which water instantly turns into vapor at sea level.
There are 2 ways water turns into steam: evaporation and boiling.
Water boils at 100ºC, as you know, and steam is formed by boiling.
Evaporation, instead, can happen at any temperature. For example, when you mop the floor, you don’t have to dry it because it dries by itself. It dries because water evaporates, and steam is being produced at like 30ºC.
100°C is the temperature at which steam bubbles can be maintained inside a body of liquid water (called “boiling”), making it evaporate a lot faster than at lower temperatures. But some water evaporates from its surface at pretty much any temperature, faster when temperature is higher.
What you see rising from the water isn’t exactly steam. Actual steam (water vapor) is invisible. The “steam” that you can see is numerous tiny water droplets which condense out of actual steam that cools off in the air above the water. They are visible in the same way that clouds and fog are visible.
There are 2 ways water turns into steam: evaporation and boiling.
Water boils at 100ºC, as you know, and steam is formed by boiling.
Evaporation, instead, can happen at any temperature. For example, when you mop the floor, you don’t have to dry it because it dries by itself. It dries because water evaporates, and steam is being produced at like 30ºC.
100°C is the temperature at which steam bubbles can be maintained inside a body of liquid water (called “boiling”), making it evaporate a lot faster than at lower temperatures. But some water evaporates from its surface at pretty much any temperature, faster when temperature is higher.
What you see rising from the water isn’t exactly steam. Actual steam (water vapor) is invisible. The “steam” that you can see is numerous tiny water droplets which condense out of actual steam that cools off in the air above the water. They are visible in the same way that clouds and fog are visible.
What’s special about 100° C?
At 100° C at sea level, the temperature of the water stops rising.
Instead, all the energy being pumped into the water gets used to convert that water to steam.
The water stays at 100° C until it is all turned to steam, and only then will the temperature begin rising again, up to over 2,000° C – – at which point it starts to break down (hydrolyze) into hydrogen and oxygen gases.
That’s why you can boil water over a campfire in a paper cup, and also why you can light a match with superheated steam.
My understanding is that steam is an invisible gas which you will get when you heat water up enough, the stuff you can see is water vapour which rather than being a gas is actually lots of extremely small water droplets suspended in the air. So, if you can see it, it ain’t steam.
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