# 3.6.1: Practice Heat to Melt or Boil

Exercise $$\PageIndex{1}$$

How much heat does it take to melt 43.77 g of copper if the copper is already at its melting point?  The heat of fusion of copper is 49 cal/g.

2100 cal  (2144.73 rounded to 2 sig. dig.)

Exercise $$\PageIndex{1}$$

How much heat does it take to boil 26.88 g of ethanol if the ethanol is already at its boiling point?  The heat of vaporization of ethanol is 853 J/g.

22900 J

Exercise $$\PageIndex{1}$$

What if you start with 85.5 g of ethanol that is only 18.5 °C?  The boiling point of ethanol is 78.4 °C. The heat of vaporization of ethanol is 853 J/g. The specific heat of ethanol is 2.46 J/g°C.

85500 J (It takes 12600 J to heat it from 18.5°C to 78.4°C plus another 72900 J to boil it.)

Exercise $$\PageIndex{1}$$

Starting with 245 g of ice that is –16.3°C, how much energy is needed to warm the ice, melt it, and warm the water to 27.2 °C?

The specific heat of ice is 0.488 cal/g°C, the specific heat of liquid water is 1.00 cal/g°C, and the heat of fusion of ice is 79.7 cal/g.