The temperature of a 150 gram drinkinh hlass decreased from

The temperature of a 150 gram drinkinh hlass decreased from 25 to 14 * C as 200 grams of water were added. Determine the original temperature of the water. (Hint: Heat loss must equal heat gain.

Solution

The original water temp is 25C, as was given in the problem... I\'m assuming you meant to ask what was the initial temp of the water that was added, which isn\'t too hard. Here goes.
Q(heat)= m(mass) x c(specific heat) x delta T(change in temp)
so Q = (150g)(4.something J/gC-look it up)(25C-14C)
Because of conservation of energy and assuming ideal insulation, the heat LOST by the 150g of water during the mixing is equal to the heat GAINED by the 200g of water. So, once you have Q, rearrange the equation to look like [delta T] = Q/mc = Q/(200g)(c)
That will give you the temperature difference between 14C and the 200g of water\'s initial temp. Delta T should come out as being positive, since the temp is going up.
When you have more complex mixtures of things with different specific heats and add processes and changes, the math becomes a lot more of a headache but the same basic principles apply just the same.