Freezing and Melting Lab

Freezing and Melting of Water Based on Physical Properties

Problem: What is the freezing point and melting point of water?

In this experiment, a test will be done to determine the freezing and melting point of water. The independent variable is the temperature of water in the beaker. The dependent variable is the state of the water in the test tube. We will be filling a beaker with ice water and adding 5 teaspoons of salt. Then the test tube will be placed in the beaker. The temperature probe will remain in the test tube for the entire lab. After 15 minutes, the test tube will be taken out, and the beaker with be filled with warm water. After holding the tube for 10 minutes, the tube will be put into the hot water. This is to examine the changes in the state of water based on its characteristics.
 

This is how the lab was set up.

Hypothesis: The freezing point of the water in the test tube will will be at 0 ºC because it is one of the physical properties of water. The melting point of water will be at 25 ºC because that is when the ice will have enough energy and warmth to turn into a liquid.

Data and Results:

The water in the test tube was partially frozen on the edges of the water. It did not turn into a complete solid ice cube; however, there was some freezing.

During the melting phase of the water, the ice on the sides quickly melted into liquid after placing it in the hot water.

Freezing and Melting Points of Water

General Temperature of Water	Temperature (ºC)
Freezing Point of Water	0.4 ºC
Melting Point of Water	18.8 ºC

These are the freezing and melting points of the water in the test tube. These were based on the flat parts of the graphs below. The melting point was 18.4 ºC higher than the freezing point. 

This is graph shows the temperature patterns for the “Melting Curve” and the “Freezing Curve.” The Freezing Curve is red, and the Melting Curve is blue. During the beginning and end of the Freezing Curve the kinetic energy decreased because the temperature decreased. However, the part of the Freezing Curve that remained constant had a decrease of potential energy because the temperature still decreased. The beginning and end of the Melting Curve had a major increase in kinetic energy, especially the end because the temperature increased. The part that stayed constant in the Melting Curve had an increase in potential energy because the temperature increased.

Conclusion: In conclusion, this experiment was successful in helping me find out the freezing and melting points of water. My hypothesis for the both the freezing point and the melting point were rejected. I was only 0.4 ºC off on my hypothesis for the freezing point, but for the melting point, I was almost 6 ºC off. Some errors that may have occurred would be that we did not stir the temperature probe enough. Also, not all of the salt had dissolved because there were still little clumps stuck to the sides and the bottom. The information I collected can be used in many other tests, as well. The same experiment could be conducted, but instead of water in the test tube, another liquid could be substituted. An experiment can be done to compare the freezing and melting point of water to the boiling point of water. In conclusion, I learned a lot about the freezing and melting point of water, and this experiment has clarified the process of change from ice to liquid H2O.