AP Thermo Test

Many of you are still trying to get by without understanding things. Q = mc deltaT doesn't do much good if you don't recognize it as the flow of thermal energy into a body. If thermal energy is conserved then for a closed system the heat into the colder elements of the system must = the heat OUT of the hotter elements. In other words its Q into the cooler = -Qinto the hotter or more clearly:

mc delta of the cooler = -mc delta T of the hotter elements.

That minus sign is all important and leaving it out shows you don't understand what the conserving of a quantity means. Many of you managed to take 75 or 85 degree water add it to 25 degree water and geta final temperature of over 100 degrees. This indicates a total lack of understanding of the meaning and behavior of thermal energy.

An easier way to find Tf for a system reaching equilibrium is to take all the Us ( mcTs), add them together and then divide by the total heat capacity ( the sum of the mc for each element). This may become too complicated when there are phase changes

Some of you suddenly introduced atmospheres as a unit of pressure with predictably disastrous results. You do not need a non-standard alternate system of units to add to your difficulties. No KMT or thermodynamic equations should be expressed in such an accidental unit.