Activity 2: Energy Needed to Melt Ice

Introduction

Ice at 0 °C is added to a measured volume of warm water. Some of the ice melts. Oncethe mixture reaches 0 °C, the volume of liquid water is measured. The additional volume comes from melted ice. Using the amount of ice melted together with thetemperature and volume of warm water, the heat of fusion of the ice is determined.

Purpose

Students will determine the energy needed to melt one gram of ice by measuring the heat lost by a known quantity of warm water when ice is placed in the water and melted.

Safety

1. Wear protective goggles throughout the laboratory activity.

2. A burner will be used to warm the water to about 50 °C. Burns are possible. Avoid contact with heated objects. Use hot pads to move warm objects. Always place warm objects where someone else will not inadvertently touch them.

Procedure

Work in pairs to accomplish the following steps.

1. Warm water to about 50 °C. Add about 100 mL to a graduated cylinder. Record the volume.

2. Pour the water into a Styrofoam Ò cup. Measure and record the temperature of the warm water to the nearest 0.2 °C.

3. Obtain several ice cubes; pat dry with a towel and immerse in the cup.

4. Cover with a lid that has a small hole near the edge. Allow to equilibrate at 0 °C by shaking and adding ice until the system is at 0 °C and excess ice remains.

5. Pour liquid water into a beaker, holding back ice that reamins.

6. Measure the volume of the liquid by pouring water from the beaker into a large graduated cylinder. Record the volume.

7. Repeat Steps 1 to 6 as instructed by your teacher.



Figure 9. Sample data table.

Data Analysis and Concept Development

Given the sample data table:

1. Determine the mass of ice melted (the density of water is one gram per milliliter).

2. Determine the change in temperature of water.

3. Calculate the energy released by the liquid water as it cooled.

4. Calculate the calories of energy required to melt one gram of ice? The specific heat of water is 1.0 cal/g °C.

5. Using the results of this experiment, determine the number of kilojoules required to melt one mole of ice.

6. Use chemical symbols in writing an equation for the fusion (melting) of ice, and include the energy term (in kJ /mole of water) as calculated in Question 5.

7. Calculate the experimental (percentage) error by comparing the experimental value which you have determined for the heat of fusion of ice to the accepted value for the heat of fusion. [6.010 kJ/mol.]

Implications and Applications

There are innumerable situations in which we try to control the temperature of foods and other materials using ice. Ice is very good for keeping materials cool in warm surroundings because is requires so much heat to melt.

When traveling in frigid locales, automobile drivers are encouraged to include kits with blankets, high energy foods that donÕt perish (such as peanut butter), and also to carry a metal cup and a candle. The cup and candle are intended to prepare emergency water by melting snow. It is dangerous and perhaps impossible to use body heat for this purpose when stranded in subfreezing weather.

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