Latent Heat of Fusion Experiment

1. Latent Heat of Fusion Experiment STARTER When heat is added to zero degree ice, the temperature of the ice and the melted water stays at zero degrees until all the ice is melted. If the heat wasn’t changing the temperature, what was it doing?

2. Latent Heat of Fusion for Water To melt ice at zero degrees into water at zero degrees, the heat added is: Q =mLf m = mass of the ice Lf = latent heat of fusion for water = 80 cal/gram We will design an experiment to determine Lf and compare our value to the accepted value.

3. Procedure Determine the mass of the empty foam calorimeter (with lid). Fill it about 1/3 full of water. Determine the mass of the water. Put the temperature probe in the water and start loggerpro and begin monitoring the water temp. Record the temperature right before you put the ice in. This is the initial water temperature Tiw. Obtain a chunk of ice ( about 2 small cubes worth). Put the ice in the water and close the lid back up. Gently swirl the water as the ice cube melts to thoroughly mix the water. Watch the temperature. When the ice has all melted it will flat line. Record this final temperature, Tf. Determine the mass of the ice that you used by reweighing the calorimeter with all of the original water and the melted ice in it.

4. Analysis – Do 2 Runs Make a data table and fill it in with your masses and temperatures. Calculate: 1. The heat that left the original water: Q1 = mwcw(Tf-Tiw) = _________ 2. The heat that warmed the melted ice water: Q2 = micecw(Tf – 0 ) = ________ 3. Conservation of energy says: Q1 + Q2 + miceLf = 0 , so Lf = -(Q1+ Q2)/mice = ________ Get the % Error = 100  Lf – 80  80 = _____________ Repeat ( 2 Runs)

5. Questions Why was Q1 negative? What does that indicate? Why was a foam calorimeter used? Why not just use a metal container? What would happen if you used too much ice?

6. Lab report Checklist Starter Data table Calculations Questions Summary