Thanks! missed the latent heat part. Is this (latent heat) expected of P4?


if the temp of the ice goes below 0 deg C, can the water in the testtube freeze and its temp continue to drop below 0 deg C too?

Tang:

http://www.postimage.org/image.php?v=aV1Sz9L9


Answer is (3).


When salt is added into the crushed ice, the temperature (Q) will drop below 0 degree C.

The water in the test tube will lose heat and freeze into ice. So temperature (P) will drop to 0 degree C.

Over time, to keep the ice in the test tube frozen, the temperature (Q) of the crushed ice rises while ice remains at 0 degree C (P).

when salt is added to the ice, the melting point of the ice is lowered, ie, it goes below 0 deg C.

That being said, I believe the ice/salt mixture will turn into water faster but I don;t think the temp will go down.

In order for the temp to go down, heat must be removed from the mixture. But from the pic, heat seems to be added to the ice since the water in the test tube gets colder.

Did I go wrong somewhere?