# About heat question which one is right?

1. Jun 16, 2014

### new hand

It is given that:

1 kg of 0 degree celsius ice is put into a cup of 0 degree celsius cold water.

is the temperature of the ice and the water remains unchanged?

or the total internal energy remains unchanged?

THX!!!

2. Jun 16, 2014

I don't think it will be cold water anymore

3. Jun 16, 2014

### Staff: Mentor

If the system is isolated, both are true.

Why? At the temperature of the phase transition, both phases coexist.

Last edited: Jun 16, 2014
4. Jun 16, 2014

Oh, I see.:shy: Thanks

5. Jun 16, 2014

### new hand

oh I forget to say
Assume there is no energy transfer between the mixture and the surroundings.

6. Jun 16, 2014

### new hand

But I think in this way,

Even if the ice melts, the energy released by the ice is not enough to lower the temperature of the water. And the temperature of the ice cannot rise because there is no heat transfer.

7. Jun 16, 2014

### Staff: Mentor

You need to add energy to ice to transform it into liquid water.

8. Jun 16, 2014

### new hand

So, will the temperature remain unchanged?

9. Jun 16, 2014

### Staff: Mentor

Yes, unless you want to violate the 0th law of thermodynamics.

Absent any chemical reaction (including dissolution), mixing two things of the same temperature together can only result in something at the same temperature.