Freezing and melting of water with Vernier Labquests

In my Science Seminar class, we are taking a look at how energy works. Energy is the capacity to do work or give off heat. All matter has kinetic energy because the atoms of a substance are constantly in motion, the measurement of that motion is what we often call the temperature of a substance. Yesterday we discussed how matter changes state when heat is applied to a substance and the relationship between kinetic and potential energy during this process. Today we conducted an experiment to verify that by completing Vernier's Freezing and Melting of Water using their LabQuest equipment. I've used this lab before and get good results. I would highly recommend purchasing their lab books if you have access to their equipment for use. I also use their probeware whenever a lab calls for a thermometer or pH probe. The equipment is easy to use and helps to develop student lab skills by the use of technology in the classroom.

Here are some pictures showing the various stages of this experiment.


The set up showing the students freezing the water.



Once the ice is frozen as shown the next step is to collect data as it is melting.



Last step in the melting process - LabQuest unit shown here.

Enzyme Activity Lab

Hydrogen Peroxide and Raw
Potato

A very quick and easy lab to observe enzyme activity is one in which you use raw and cooked potatoes and hydrogen peroxide. Hydrogen peroxide is made as a by-product in cellular processes, it is toxic to cells and that is where the enzyme catalase comes in. The function of catalase is to decompose hydrogen peroxide into water and oxygen gas. You've observed this if you've ever used hydrogen peroxide to disinfect a cut or scrape. Students can observe the activity of the catalase by looking for the bubbles of oxygen that are released.

Enzymes which are a class of proteins are subject to the threat of denaturation, or the loss of their 3-D structure, when exposed to changes in pH or heat. In this lab I have the students mix in some vinegar into the hydrogen peroxide to lower the pH of the environment. As a result there is a visible slowing down of the reaction. We also use a baking soda solution to create an alkaline environment but the enzyme isn't impacted as much. Lastly, I have them test a piece of cooked potato. In the cooking process the catalase is denatured and there is no activity at all.

Hydrogen peroxide and
cooked potato

We have been investing in Vernier Lab Quest equipment for student data collection. Using a very crude methodology, I had the students stopper up the test tubes and use the Gas Pressure Sensor to observe any pressure changes that result from the release of the oxygen from the decomposition reaction. It worked. Clearly there was a significant pressure change with the raw potato and hydrogen peroxide, less change with the vinegar mixed in, and absolutely no change in pressure when the cooked potato was tested. Vernier does put out a series of experimental procedures that are more sophisticated and quantifiable. In this case I was focused on the students learning the key concepts of enzymes (active site, activation energy, catalyst) and the conditions that will lead to protein denaturation.

Testing for pressure change using a Vernier Lab Quest
with a Gas Pressure Sensor.