# Question #3c48f

##### 1 Answer

Here's what I got.

#### Explanation:

The key here is the **specific heat** of water, which is usually given as

#c = "4.18 J g"^(-1)""^@"C"^(-1)#

The specific heat of a substance is the amount of heat that must be provided in order to increase the temperature of

In your case, you need to provide

Now, the problem provides you the amount of heat that you have at your disposal and the desired *change in temperature*, which is equal to

#DeltaT = 75.0^@"C" - 20.0^@"C" = 55.0^@"C"#

Use the specific heat of water to calculate how much heat would be needed in order to increase the temperature of

#55.0 color(red)(cancel(color(black)(""^@"C"))) * "4.18 J"/("1 g" * 1color(red)(cancel(color(black)(""^@"C")))) = "229.9 J g"^(-1)#

So, you must add **for every**

#8000 color(red)(cancel(color(black)("J"))) * overbrace("1 g"/(229.9 color(red)(cancel(color(black)("J")))))^(color(blue)("needed for 55" ""^@"C increase")) = color(darkgreen)(ul(color(black)("35.8 g")))#

I'll leave the answer rounded to three **sig figs**, but keep in mind that you only provided one significant figure for the amount of heat you have at your disposal.