latent heat of boiling water

[kenny1999]

It's said latent heat of boiling water or steam will cause more damage.

I find that when I cook and the water is boiling, if I put my hand near the steam I wouldn't get as much pain as I accidentally put my hand directly into the boiling water. I would probably hold on a few seconds under the steam but if I put my hand into the boiling water I won't be able to withstand one second.

Why is that?

Edited November 4, 2022 by kenny1999

[Bufofrog]

Because the water is much more dense than the steam.  In other words there are many more high temperature molecules in contact with your skin in water than in steam, therefore much more heat is transferred to your skin from the water.

[sethoflagos]

On 11/4/2022 at 10:33 AM, kenny1999 said:

It's said latent heat of boiling water or steam will cause more damage.

I find that when I cook and the water is boiling, if I put my hand near the steam I wouldn't get as much pain as I accidentally put my hand directly into the boiling water. I would probably hold on a few seconds under the steam but if I put my hand into the boiling water I won't be able to withstand one second.

Why is that?

What @Bufofrog says is true.

And yet condensing steam can readily provide the highest heat transfer coefficients commonly found in industrial processes, often up to 15,000 Wm^-2K^-1. This is typically 5 times higher than for liquid heat transfer media.

Another factor to consider is that the strong thermal convection above your cooking pot draws a lot of air into the steam rising from it that both cools it and provides a partially insulating 'mitten'. 

Immersing your hand in a stream of pure dry saturated steam would be an altogether different experience. Not to be tried at home or anywhere else for that matter. 

[exchemist]

On 11/4/2022 at 9:33 AM, kenny1999 said:

It's said latent heat of boiling water or steam will cause more damage.

I find that when I cook and the water is boiling, if I put my hand near the steam I wouldn't get as much pain as I accidentally put my hand directly into the boiling water. I would probably hold on a few seconds under the steam but if I put my hand into the boiling water I won't be able to withstand one second.

Why is that?

When you put your hand near what you may think is steam, it is just condensed water droplets. For real steam, i.e. vapour at 100C, you would need to put your hand into the invisible stream issuing from the spout of a vigorously boiling kettle, i.e. the inch or so before it becomes visible as a cloud of "steam". If you ever do that, you will scream and need to see a doctor: the scald will be far more intense than from boiling water. Do not try it. That's because of the latent heat.

[Bufofrog]

38 minutes ago, exchemist said:

the scald will be far more intense than from boiling water.

Agreed, I stand corrected.