4A.7

[Skyllar Kuppinger 1F]

"calculate the heat that must be supplied to a copper kettle of mass 400.0g containing 300.0g of water to raise its temperature from 20.0 degrees Celsius to the boiling point of water, 100.0 degrees Celsius."

the answer manual just does q=mcdeltaT for both copper and water and adds them up. they use the same delta t (80 degrees) for both the copper and the water. But how do you know that the water is going to be the same temperature as the copper in the kettle surrounding it?

[Sanjana Munagala_1j]

I believe you would treat the kettle and the water as one whole system and everything around it as the surrounding. Because you treat them as one, you can simply add the heat changes for both of them, assuming constant pressure. Heat at constant pressure is enthalpy which is a state function and thus you are allowed to add the individual enthalpies.

Hope that helps!

[chari_maya 3B]

Is it possible to do this problem by finding total mass and only applying mcdeltaT once, or would that not work because of different heat capacities?

[ASetlur_1G]

Is it possible to do this problem by finding total mass and only applying mcdeltaT once, or would that not work because of different heat capacities?

I think you have to do them separately because copper and water have different heat capacities.