If steam is hotter than boiling water, then why doesn't water steam after water boils?

Question

Why doesn't water boil first? I know for a fact that steam is hotter. But you always see steam several minutes before the water boils. Why?

Answer 1

That's water vapor you're seeing, not steam.

Answer 2

A few things:

1. you can't see steam, steam is invisible -- what you can see is the tiny water droplets that form as steam cools down and condenses into tiny visible water droplets that look like smoke

2. at a given pressure like in the open atmosphere, steam can be exactly the same temperature as boiling water, or hotter

if you heat water it will eventually boil into steam (at about 212 degrees F at normal pressure) the steam will also be 212 deg, if you continue to heat the steam, it will become hotter and hotter steam

Water has a vapor pressure at all temperatures. Some liquid water will turn into water vapor before the water starts boiling. Some of that vapor (steam) will condense and look like the smokey droplets that indicate steam is there

Remember water at room temperature will eventually evaporate. As you heat it up it evaporates more quickly and that is what you see above the pan of water before boiling.

Boiling point is defined as the place when the vapor pressure of the liquid becomes equal to the atmospheric pressure.

I hope I have answered the question you were trying to ask.

Answer 3

If you have water in a pan on a heat source. Heat rises. So the surface of the water is hotter then the the water under the surface. You are seeing the surface faporizing before you see the lower water boil. Which the boiling action is caused by the water at the bottom at some point is hotter then the above water.
You are actually seeing steam in bubble-form rising to the top to be released.

Answer 4

Hello:
I am going to wade in on this question. I hope it will help.
When heating any substance it will go through a series of transitions. Lets start at the begining.

Solid: As you heat a solid up it will steadly get warm and slowly get hotter.At some point the solid starts to melt but is not getting warmer.This point is called the heat of fusion. This is the heat needed to change the solid to a liquid but no temperature changed is observed. Melting point is the temperature where the rate of a solid melting and the rate of a liquid freezing is the same.

Liquid: Once a substance is completely a liquid the temperature will now continue rise. Once the liquid temperture gets high enough. The liquid will under go its own transition. Where more heat is added but the temperature is not changing. The liquid is changing into a vapour. The heat required to do this is called the heat of vapourization. Once this level of heat has been absorbed the liquid will vapourize. It is this extra bit of heat in the vapour that makes the vapour hotter then corresponding liquid at a the same temperature.

Vapour: The temperature once again contninues to rise.

So yes steam is hotter then boiling water. The water vapour you see is the water that has manged to be vapourized at that point in time. The vapourization rate will continue to increase as the temperature of the water increases.

Water can only boil once it's boiling point is reached.

Answer 5

Its because at that point,the water vapor being released by the boiling water,condenses into steam,which is only visible during that range of temperature...tom science

Answer 6

there are several points you have to remember , 1st pressure plays a major part in qwhat tempo water boils. 2ndly , when water boils it actually a bit , cos energy is needed to release water from the surface tension of the water and evaporation causes cooling, so as water boils (ie evaporates) the temp of the water actually drops

Answer 7

The boiling water has diff. temp. .At some places water heats up before& we see steam rising.

After all it's heat that matters

Answer 8

that water did boil.

there are several parts of water at varying temperatures

the hottest parts rise, then turn to steam.

Answer 9

water does not need to boil to evaporate. heating it up is enough. what you see is condensation from this vapor coming in contact with colder air above the pot - kinda same stuff that the clouds are made of

Answer 10

What you see is not steam but water vapor