# 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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