Which is more useful in storing thermal energy: metal or an equal weight of water?

Question

explain why..

Answer 1

we think it's metal

Answer 2

I agree with billruss. and also with david h, but would like to add that the reason water's heat capacity is greater is that water has more degrees of freedom per unit weight.

i.e. more enthropy in 1kg of water than in 1kg of copper.

Temperature can be thought of as the average kinetic energy per degree of freedom, and since water has a lower molar mass than most metals, and since the water molecules have more freedom to change orientation, more heat is needed to give the average degree of freedom in water tha same amount of energy.

Answer 3

specific heat of water is 4200 J/kgC, which means 1 kg of water takes 420 kjoules to heat it up by 100 degrees

Aluminum is 900 J/kgC which means 1 kg of water takes 90 kjoules to heat it up by 100 degrees

Copper is 386 J/kgC

So water is 5 times or more efficient at storing thermal energy.

More useful? depends on the application.

Why? it's the property of the materials. Properties don't have reasons, they just are.

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Answer 4

It depends on the application, for example if i were to use a soldering iron , i could heat up the iron to 600 degrees c in a fire then take it too the job to be soldered.This would be impossibe using water as water will boil at 100c.

However by the same token water will be more usefull to heat your house and store hot water i a cylinder and pump it around radiators, very difficult to do with a solid metal !