Ecology: Water's Heat of Fusion

Determine the freezing and melting point of water and see what happens to temperature during the phase change.

Motion Sensors

Students can see temperature changes and periods of stability that occur during the phase changes of water. Enlarge graph.

Lab Summary:

In this exploration, students will use a sensor to record the temperature of water as it freezes and melts.

They will observe that as water changes phase from liquid to solid, it first enters a super-cooled state with a temperature below 0°C.

When the water begins to change phase into a solid (ice), an exothermic process occurs. The water temperature suddenly jumps up to 0°C. This exothermic process continues, keeping the water at 0°C, until all the molecules have joined the solid phase. When the water has reached the solid phase, the exothermic process stops. The temperature of the ice then decreases to that of the surrounding salt water ice bath, about –6°C or –7°C. When the ice is removed from the salt water ice bath, its temperature quickly increases to about 1°C to 2°C, where it stabilizes or rises slowly until all the ice is melted. The process of melting is an endothermic process that absorbs heat, preventing the temperature of the ice water from increasing to the surrounding temperature. As soon as all the ice has melted, the temperature of the liquid water rapidly increases to that of the surrounding air or water.

Download Free Lab  (PDF, 472 KB)

(student version)

Method:

Use a Temperature Sensor, to investigate the heat of fusion of water.

Here's What You Need:

Probeware

Other Materials

  • Test Tube, Medium
  • Rubber Stopper (#1) with small hole
  • Erlenmeyer Flask, 250-mL
  • Thermos™ Insulated Container
  • Large Wooden Spoon (for stirring ice bath)
  • Ruler, Metric
  • Pen
  • Protective Gear
  • Ice, 50.0 g
  • Rock Salt, 225.0 g
  • Water, 1.0 L

Lab Manual:

This activity is included in Explorations in Biology (PS-2807), complete with Teacher Information pages, student instructions and handouts, and sample data for a total of 25 probeware-based labs. For your convenience, we offer bundles which provide the probeware necessary for the activities in the manual. For more information on these resources and bundles, click here.