How many grams of cold water necessary to lower temperature in container

Paulo Serrano

1. Homework Statement
How many grams of 20 degree C water do I need to add to 100 grams of 80 degree C of water to get the final temperature down to 50 degrees C?

2. Homework Equations
I'm sure it's a pretty simple equation, but I don't know it. (I'm studying a lot of different things at once and am not in school)

3. The Attempt at a Solution
Not sure.

Thanks :)

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w3390

First you need to know the equation for energy, which is q=c*m*deltaT, where deltaT is T(final)-T(initial). You also know that q of the 20 degree water equals the negative of the 80 degree water. Given this, you should be able to solve for grams of 20 degree water.

Paulo Serrano

q is heat energy, correct? Why is one the negative of the other?

w3390

One is negative of the other because the heat that leaves the 80 degree water is added to the 20 degree water.

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