March+16-20+2009+Week+3



1. It takes 36 kJ to melt a sample of ice. How much did it weigh.

2. How much heat is required to change a 37.9 g ice cube from ice at -11.6°C to steam at 131°C?

The heat of fusion of water is 6.02 kj/mol. The heat of vaporization of water is 40.7 kJ/mol. The heat capacity of ice is 2.11 kJ per kg K (kJ per kilogram per degree kelvin). The heat capacity of water is 4.187 kJ/Kg K. The heat capacity of steam is 1.996 kJ per kg K.

3. Make an excel spreadsheet for question 2. I want you to use excel to make a program that will allow you to simply figure out how much energy is required to change cold ice to hot steam. I also want to see the percentage of energy used to change the temperature, percent of energy used to convert ice to a liquid, and the percent of energy used to turn hot water into steam.

Don't forget that to change the temperature of a sample use the equation q= mc(delta)T

ie heat is equal to the mass times the specific heat times the change in temperature.

Answer: Total energy required = 117kJ

3a. Look at your percents Write a quick sentence or two explaining where the energy went.

4. You just figured out how much heat is required to change cold ice to hot steam. Do the same problem but start at 0C ice and turn it into 100C steam. What percentage of the energy went into melting the ice, boiling the water, and changing the temperature from 0-->100? (you should be able to solve this very quickly using your excel spreadsheet).

1. 107.6g