# What mass of water would release 16700J of energy when freezing?

##### 1 Answer

#### Answer:

#### Explanation:

Your tool of choice here will be the *enthalpy of fusion*,

For a given substance, the enthalpy of fusion tells you how much heat is either **needed** to melt **given off** to freeze

Water has an enthalpy of fusion equal to

#DeltaH_"fus" = "333.55 J"#

https://en.wikipedia.org/wiki/Enthalpy_of_fusion

This tells you that when *liquid* at its freezing point to *solid* at its freezing point, **given off**.

In your case, you know that **given off** when a mass of water undergoes a liquid *phase change* at

Use the enthalpy change of fusion as a **conversion factor** to determine how many grams of liquid water would give off this much heat when freezing

#"16,700" color(red)(cancel(color(black)("J"))) * overbrace(("1 g H"_ 2"O")/(333.55 color(red)(cancel(color(black)("J")))))^(color(blue)(= DeltaH_"fus")) = color(green)(|bar(ul(color(white)(a/a)color(black)("50.1 g H"_2"O")color(white)(a/a)|)))#

The answer is rounded to three **sig figs**, the number of sig figs you have for the heat given off.