Which is hotter; 100 Degrees Celcius 'Water', OR 100 Degrees Celcius 'Water Steam(Stuff that comes out of a kettle)'

[EndCredits]

My 15-year-old sister is convinced that 100 Degrees Celcius 'Water Steam(Stuff that comes out of a kettle)' is hotter than 100 Degrees Celcius 'Water'

 

I tried to straighten her up, but she wouldn't believe it. I then tried my last resort:

 

Comparing the question with the 'Which is heavier; A tonne of Bricks or a Tonne of Feathers' question.

 

100 Degrees is obviously the sane as 100 degrees, and a tonne is obviously the same as a tonne, it would just take alot more feathers.

 

If you want one more question to answer, here is another obvious question:

 

Which is louder; A 88 decibel motor engine, or a 88 decibel scream?

 

Yes, the above question probably couldn't fully happen, but this is just theory.

 

So, if someone can prove me wrong that the question titled isn't the same amount of heat, please prove me wrong!

[Cap'n Refsmmat]

If the two are at 100 degrees Celsius, it's of course true that neither is hotter than the other. However, one must remember that there can be a difference between "hotter" and "feels hotter", depending on the heat capacity and conductivity of the material. For example, reach into a 400-degree oven and your hand won't be burned by the hot air -- but grab the 400-degree metal pan with your bare hands and you'll end up with some blisters. The pan, with a higher specific heat capacity, can transfer more energy into your hands than the air can, despite being at the same temperature.

 

It's also possible to heat up steam past 100 degrees Celsius, although I don't think that commonly happens in a boiling pot or kettle.

[Moontanman]

Which is louder; A 88 decibel motor engine, or a 88 decibel scream?

 

To a human the scream is worse as far as how it sounds but both would contain the same amount of sound energy.

[Janus]

My 15-year-old sister is convinced that 100 Degrees Celcius 'Water Steam(Stuff that comes out of a kettle)' is hotter than 100 Degrees Celcius 'Water'

 

I tried to straighten her up, but she wouldn't believe it. I then tried my last resort:

 

Comparing the question with the 'Which is heavier; A tonne of Bricks or a Tonne of Feathers' question.

 

100 Degrees is obviously the sane as 100 degrees, and a tonne is obviously the same as a tonne, it would just take alot more feathers.

 

If you want one more question to answer, here is another obvious question:

 

Which is louder; A 88 decibel motor engine, or a 88 decibel scream?

 

Yes, the above question probably couldn't fully happen, but this is just theory.

 

So, if someone can prove me wrong that the question titled isn't the same amount of heat, please prove me wrong!

 

An mass of 100° steam does contain more heat than an equal mass of 100° water. This is due to the heat of vaporization needed to convert water to steam. This works out to being ~540 kilo-calories per kilogram. Put another way, it takes over 5 times as much heat to convert water to steam than it does to initially raise the water's temperature from 0 to 100°. That heat is released when the steam condenses.

[ewmon]

Comparing the question with the 'Which is heavier; A tonne of Bricks or a Tonne of Feathers' question.

BTW, this trick question has evolved in many ways, but it was once:

 

Which is heavier, a pound of gold or a pound of feathers?

The answer is a pound of feathers.

Feathers are measured using the avoirdupois system (ie, 16 oz per pound).

Gold is measured using the troy system (ie, 12 oz per pound).

16 oz is greater than 12 oz; thus, a pound of feathers is heavier.

[CaptainPanic]

Cap'n Refsmmat, for the most part your post is correct... but there are a few things I'd like to correct or add:

If the two are at 100 degrees Celsius, it's of course true that neither is hotter than the other. However, one must remember that there can be a difference between "hotter" and "feels hotter", depending on the heat capacity and conductivity of the material. For example, reach into a 400-degree oven and your hand won't be burned by the hot air -- but grab the 400-degree metal pan with your bare hands and you'll end up with some blisters. The pan, with a higher specific heat capacity, can transfer more energy into your hands than the air can, despite being at the same temperature.

The reason that the pan will burn your hand, and hot air won't is not the heat capacity. It's especially the heat transfer that is much higher between your hand and the metal surface. Heat transfer is independent of heat capacity... and metals actually have a really low heat capacity (the heat capacity of iron (460 J/kgK) is 9 times lower than liquid water (4180 J/kgK), and 4.3 times lower than that of steam (2000 J/kgK)).

Gases normally have a really low heat transfer coefficient but will often have a very normal heat capacity similar to liquids or other (non-metallic) solid materials. Heat transfer from a gas to a liquid/or solid can typically be 10-20 times lower than between liquid/liquid or solid/liquid, but the difference depends heavily on things like mixing/stirring or the liquid and gas phases... and this can easily be an order of magnitude different from what I say here.

 

However, regardless of mixing/stirring, metals typically have the highest heat conductivity of all materials. The 'heat conductivity' or 'thermal conductivity' of materials is listed here.

The "heat transfer" describes the transfer of energy from one material to another. Heat conductivity describes how easily a material can conduct the heat internally.

 

It's also possible to heat up steam past 100 degrees Celsius, although I don't think that commonly happens in a boiling pot or kettle.

In the presence of liquid water, you can never heat the steam to a higher temperature than the boiling point of the water (i.e. 100 deg C).

You can only superheat the steam if you bring the steam into contact with a heat source outside the kettle itself. Read more about superheaters (in steam engines) here - it's a bit off topic though, so I'll leave it at this.

 

Anyway, 100 deg C is 100 deg C, regardless of the material, or its state (gas / liquid).