# Water density and temperature

1. Jun 21, 2005

### jazzchan

Dear all

Here is a question i need to help

Can I know how much water at 25^C to put into a water at 75^C and then the mixture is 60^C ??

thanks and best regards

Jazz

2. Jun 21, 2005

### VietDao29

Use
$$Q = mc\Delta t$$
Viet Dao,

3. Jun 21, 2005

### jazzchan

is it mean the Q of temperature from 75 to 60^c is equal to the Q of 25 to 60^C ??

thank

4. Jun 21, 2005

### HallsofIvy

Staff Emeritus
Since we are dealing with water of a constant heat capacity, it's not the complicated. You can treat it as a "mixture" problem. If you have x cm 3 of 25 degree water, the heat is proportional to 25x. If you have y cm3 of 75 degree water, the heat is proportional to 75y. Mixing those together you have x+ y cm3 of water that you want to be 60 degrees so the mixture's hear is proportional to 60(x+y). You want 25x+ 75y= 60(x+y). Of course, that's one equation in two unknowns because you didn't say how much of the 25 degree water you had or how much water you wanted to end up with.

5. Jun 21, 2005

### jazzchan

yes...my question is to find how much 25 degree water should be used...

would u tell me more ??

thanks...