Steam vs water at the same temperature

[daveed]

if steam and water are both at 100 degrees celsius, why would the steam scald you more, even if they both have the same kinetic energy?

 

[DB]

Do you mean steam as in evaporized water? Because I don' think it's possible to have water and water vapor at the same temperature. Heat is energy and would give water vapor a stronger energy than room temp. water. Making it more likely to scald you. Heat is needed to evaporate water.

I think that's what you were asking.

 

[DB]

Oh ya, I'm pretty sure, the more kinetic energy the more heat it emits. (Kinetic Energy of molecule i.e H20, having more motion, therefore more kinectic energy)

 

[russ_watters]

if steam and water are both at 100 degrees celsius, why would the steam scald you more, even if they both have the same kinetic energy?

Steam has more energy than water because it takes energy to break the bonds that keep it a liquid. When steam hits you, some of it condenses, and your skin absorbs all that extra energy.

 

[Clausius2]

Because I don' think it's possible to have water and water vapor at the same temperature.

That's false, you can have a mixture of steam and water (vapor) at the same temperature, just the temperature of change of state.

Steam has more energy than water because it takes energy to break the bonds that keep it a liquid. When steam hits you, some of it condenses, and your skin absorbs all that extra energy.

That's a good explanation. It sounds good.

 

[sheldon]

is it called superheated?

 

[brewnog]

No. It's superheated once there is no longer a dryness fraction (ie once all the liquid water in the mixture has evaporated, or when the steam is 'dry'.). This is the region beyond the saturation line on a Ts diagram of water boiling.

 

[Dual Op Amp]

Once water reached it's evaporation point, it changes into steam, and floats away into the air. This small amount of water reduces the overall temperature of water to 212 degrees F. This means no matter what water's temperature will not exceed 212 degrees F. For example, if you put a cup of water in an oven at 400 degrees F, the water would be 212 degrees F. Why? Because as, water heats to it's evaporation point, (212) it turns to steam. Steam is less dense than air, so it rises away from the cup. This reduces the overall temperature of the water, making it stay at a temperature of 212 degrees F or 100 C.

 

[brewnog]

This means no matter what water's temperature will not exceed 212 degrees F.

This is not true. Water could easily exceed this temperature, if the pressure was allowed to rise above atmospheric. For example, at 4.7atm, the boiling point of water is roughly 150 degrees Celcius.

 

[russ_watters]

This is misleading at best:

Once water reached it's evaporation point, it changes into steam, and floats away into the air.

When a specific mass of water reaches 100C, it isn't even close to having enough energy for all of it to turn to steam. It takes 539 cal/gram to boil water that is already at its boiling point, but to raise it one degree C (to get to the boiling point) only takes 1 cal/gram.

 

[OddThoughts]

if steam and water are both at 100 degrees celsius, why would the steam scald you more, even if they both have the same kinetic energy?

At standard atmospheric pressure, usually accepted as 14.7 psi, at 100 deg C. water boils and steam condenses simultaneously, 100 C is the max temperature water can reach at this pressure and it is the minimum temperature that steam can exist at this pressure. Therefore it is possible for steam to exist at many times the max temperature of water.

 

[laestat]

the owen is a constant heating device, water upon constant heating beyond the Tsat will yield to super-heated tendencies, meaning the cup becomes empty & the owen is filled with steam at super-heated temperatures and the pressure rises. The Latent heat of vapourization is surpassed by constant heating easily..

 

[Drakkith]

Nov21-04, 03:12 PM <---Whew! Long time ago that this thread was brought up for air!

 

[DaveC426913]

Indeed. And it seems gibberish to me.

What's an owen?

 

[Bloodthunder]

Probably an oven.

 

[laestat]

sorry. its oven, my bad..

 

[DaveC426913]

Ok, but I still don't get how your post is shedding any light on the topic.

I guess it doesn't matter; the thread's 7 years old.

 

[laestat]

just a random browse n got into it..didnt get to see when were these published in the forum..