Materials

Immersion Heater

600 ml beaker (to hold Styrofoam cup)

Large Styrofoam cup

Stopwatch

Digital Thermometer

Laptop (for graphs)

Introduction

In this lab we will explore some concepts of heat and its relationship to temperature change.

Safety

In this lab we will make use of immersion heaters. Immersion heaters must be immersed in water before they are plugged in. If you plug them in without first immersing them, they will glow red hot and possibly melt, presenting a considerable risk of burning you and also of possibly starting a fire. Be sure to have the immersion heater plugged in only during the indicated times during the procedure. Also, always make sure that the immersion heater is not immersed beyond the bottom of the plastic handle. (You want it in the water but not too much!)

Preliminary Questions

Answer the following before conducting the experiment.

Q1. We will start with a mixture of ice and water at 0 C°. When you first plug in the immersion heater sketch what you think a graph of temperature vs. time will look like.

Explain why you think your graph will look like this.

Q2. Once all of the ice has melted, sketch what you think a graph of temperature vs. time will look like as you continue heating with the immersion heater. Explain why you think your graph will look like this.

Procedure

1. Set-up

A large reservoir of ice and water at equilibrium should be available at the front of the room. Place the tips of your digital thermometer and immersion heater into the reservoir so that they have time to equilibrate.

Q3. Record the appropriate power rating of the heater.

Power Rating: _______________

You want the ice and water to remain at equilibrium for the start of the experiment so perform the following steps rapidly.

Q4. Determine the mass of the Styrofoam cup.

Perform the following steps as rapidly as possible.

Fill the Styrofoam cup from the reservoir with 150 ml of water (no ice) and determine the mass of the cup and water. Use a paper towel to dry 200 ml of ice and then add it to the water in the Styrofoam cup. Determine the mass of ice, water, and cup.

Mass of Cup: _______________

Mass of Cup + Water: _______________

Mass of Cup + Water + Ice: _______________

Mass of Water: ______________

Mass of Ice: ______________

2. Start Acquiring Data

Place the cup into the beaker to keep it from falling over. Recover your thermometer and immersion heater, and place them into your cup. Record the initial temperature of your water in the data table (next page). Simultaneously plug in your immersion heater and start the stopwatch. Stir the water continuously and record the temperature every 20 seconds in the table below. Also carefully observe the ice and record the time at which all of the ice melted. Once the ice has melted, continue stirring and recording the temperature at one minute intervals for 5 minutes after the ice has melted. Unplug the immersion heater at this point.

Q5. Data Table

Time (s)	Temperature (°C)
0

Q6. Elapsed time at which ice melted: _______________

Questions and Data Analysis

Q7. Use Excel or LoggerPro to make a properly labeled graph of Temperature vs. time. Attach the graph.

Q8. Did the portion of the graph when the ice was melting match what you expected? (Q1). Explain.

Q9. Did the portion of the graph when the water was heating match what you expected? (Q2) Explain.

Q10. Explain how you can use the elapsed time at which the ice had melted and the power rating of the immersion heater to find the total energy added to the ice to melt it. Find the total energy added to the ice.

Q11. The latent heat of fusion is defined as the energy per mass needed to turn a solid substance at its melting point into liquid. Use your answer to Q10 and the appropriate mass to determine the latent heat of fusion for water.

Q12. Look up the accepted value of the latent heat of fusion for water and compute the percent difference between the value you’ve found and the accepted value.

Q13. How well did your value agree with the accepted value? Discuss any reasonable sources of error. In particular were there any sources of heating that we did not take into account? Do not use catchalls. Be specific.