If I put a cup of water in an oven proof container and boil it in an oven at 400 degrees, and then do it with an oven at 500 degrees,
Will the hotter oven evaporate the water faster?
My thought is it will all evaporate at 212 but the hotter oven would make it to 212 faster. Aside from that, would a hotter temp make it happen faster if all other things were equal?
In: Chemistry
Water needs on average 4.2 kilojoules per kilogram to raise the temperature by 1 degree Celcius between freezing and boiling.
To fully evaporate 1 kilogram of water at 100 degrees Celcius to 1 kilogram of steam, you need 2256 kilojoules.
Water cannot exist at 101 degrees Celcius at ambient pressures, so before the “mixture” can reach 101 degrees Celcius, it would all have to have evaporated.
The speed of evaporation is purely dependent on the rate at which heat is added. A 2kW element would take twice as long to boil the water than a 4kW element.
The only place where the thermostat becomes relevant is if the cup you’re boiling the water in is an insulator and heat cannot get into the cup fast enough – so the environment temperature causes the thermostat to swirch off until the environment cools down.
The water will reach the boiling point and stay at exactly there regardless of how hot the environment is. Cranking up the heat just makes it boil faster, but the water itself doesn’t go past 100C until it’s been vaporized.
The hotter the oven the faster the water will typically evaporate.
Once water reaches the boiling point at 212F it cannot get any hotter, however any heat energy that it gets from the oven will be used to evaporate water(which takes quite a lot of energy), so the more heat energy the more evaporation.
If you pour a little water into a hot pan, it will boil immediately. If you add more water, the thermal mass of the water exceeds the heat the pan is putting out, and can cool the pan. Same volume of water on a much bigger surface at the same temperature would also boil instantly, because you’ve applied much more heat to it.
Take it to an extreme comparison, one is a small camping stove slowly boiling a pot of water, the other is dropping a pot of water into the Sun. It would be weird if the nuclear furnace in the Sun *couldn’t* evaporate the water any faster than the small camping stove. If the pot was just sitting there, not melting, not evaporating, in the Sun for a couple of hours slowly steaming because the more energy couldn’t do anything to the water.
Another weird comparison is heating up steel red hot so it has some amount of energy in it – then dunking it in water, like a blacksmith does when making a horseshoe or sword. It hisses as the water next to it flashes to steam. Now heat up an Ocean Liner red hot and dunk it in the ocean. There’s a lot more energy involved in getting the Ocean Liner red hot because it’s so much bigger, imagine if it only hissed with a tiny poker’s worth of water flashing to steam from one end and nothing else happened and it just did that for months.
That the more energy somehow *couldn’t* evaporate more water per second. That would be really weird.
Yes, the more heat energy you can get into the water, the faster the water will evaporate away. The outside of the pot gets hot, the heat conducts through the pot, and into the water. The higher the heat difference, the faster conduction happens. The water touching the pot gets more energy more quickly from a more energetic (hotter) pot wall, that makes it evaporate more quickly and get out of the way of the rest of the water, which touches the pot quicker, heats up quicker. Same with the air to water boundary, the hotter air is molecules moving faster, hammering into the surface of the water more energetically, shoving more energy into the water more quickly.
Heat transfer is proportional to the difference in temperature. The water will be 212 degrees and receiving heat from the hotter air around it. Each unit of heat evaporates a certain amount of water. If we assume the oven is able to maintain the air at the set temperature, then 500 degrees will transfer heat into the water about 50% faster, and thus boil away the water about 50% faster.
Yes, hotter temperatures do make water evaporate faster when you’re cooking. Imagine you’re at a pool party on a hot day vs. a cool day. On the hot day, you’d dry off much quicker when you get out of the pool. The same idea applies to cooking.
When you’re cooking and the stove is set to a high temperature, it’s like turning up the sun at the pool party. The water in the pot gets really hot, and the heat gives energy to the water molecules. This energy makes the molecules move faster and faster until they have enough power to break away from the rest and jump into the air as steam.
So, the hotter the burner, the more energy the water molecules get, and the faster they turn into steam and evaporate. That’s why boiling water on a high setting makes it disappear faster than on a low setting.
Yep, you can see this effect boiling water on a stove. At a low simmer you’ll see little wisps of steam, but on full high you’ll see a big column of steam rushing out. That’s the water evaporating faster.
You can also feel it—it’s no problem to wave your hand through the simmer-level wisps of steam, or even bend right down and smell what you’re cooking, but you could easily scald yourself doing the same over a pot set to high (please don’t try this). That’s where all that extra energy is going.
Assuming standard pressure, water can evaporate at room temperature, this is because of a thing called vapor pressure.
Vapor pressure is the tendency for a liquid to turn into a gas. Basically any liquid with heat (i.e. anything above absolute zero), the molecules of the liquid will be moving; the more heat, the faster the movement. The more movement, the more likely it is that an individual molecule will be able to break away from the rest. This breaking away is evaporation.
So, it would stand to reason that the more heat applied when cooking will cause the water molecules to move faster, and thus evaporate sooner.
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