Convection Current Experiments

At the end of the last class period, I assigned a small homework assignment. I wanted each student to define four terms. Unfortunately only about 7 of 25 students attempted the homework assignment.

On day two of the class, I we did an experiment where the students placed one drop of food coloring into clear plastic plate filled with water. The drop of food coloring was allowed to settle in the water and then the plated was placed over a warmer cup of water. The heat from this warm cup of water heated the plate and forced convection to begin occurring inside the fluid. The students were given the task of drawing a picture of the movement of the dye every thirty seconds. If the students watched carefully, they would be able to observe the convective current motion in the water in the plate.

Unfortunately, this experiment did not go quite as planned. Towards the end of my lecture in the previous class, I showed the students the necessary steps to complete the lab. I also typed up protocols for each group to follow. Nonetheless, on the day of experimentation, more than half of the class did not know what to do. Placing the first drop of dye in the water was something that had to be done with extreme care. Most of the groups had difficulty with this step, and with so many groups, I just ended up running around to each station and placing their first drop of dye for them. With so many students asking me questions and saying that they were ready for the next step, it felt slightly chaotic. I think I could have done a better job of organizing how each group would proceed through the experiment. Also, I needed to think of a better way to describe how to place the drop of dye in the water. At the halfway point through the class, most groups had completed the experiment. As the dye began to move, I went to each group and asked them questions to make sure they were grasping the important concepts from the experiment. Through discussion, we realized that the dye was being warmed which caused it to rise and expand.

After everyone completed the experiment and cleaned up, I re-did the experiment in front of the class and we discussed what they were supposed to observe. I asked the class what our observations were (dye rising and expanding) and what must have caused this. The rest of the hour, I tried to connect the concept of the convection that we saw occurring inside the plate with the convection that occurs inside the earth’s mantle. Again, the class was very attentive and participated when I asked them questions. It really seemed like those students interested in connecting the concepts together did so successfully. I could see the learning process taking place right before my eyes. It’s very interesting to ask a student to draw a pure conclusion based off an observation they’ve just made, watch their expressions as they think and mentally connect the dots, and then, deliver a conclusion that is in fact correct. It’s like you can see the knowledge being formed in their minds.

A few general observations that I made…

First, the students are very disinterested in doing homework. They won’t even complete small assignments that are essentially free points. Also, the students have an aversion to reading protocols. Even though each group had a set of instructions at their stations, very few took the initiative to read the protocols. Mr. Sowder and I discussed this after the class, and he mentioned that this is common in other science classes as well. During the class, as I wrote notes on the board, I heard several moans and groans from students about the amount of information I was putting on the board. For some reason, these students strongly dislike taking notes. I don’t think that they see a benefit in writing down what the teacher is writing on the board. I got the feeling that they preferred to just watch me as if I were a performer. They certainly have yet to understand the role that taking notes and reviewing them plays in the learning process.

One of the more interesting and accidental observations that I made happened in the morning while I was setting up for the day’s activities. Mr. Sowder’s first hour is a biology class. Much to my surprise of the 25 students in the class, only 2 students were male. For freshmen biology is considered an advanced class. Mr. Sowder’s 2^nd and 4^th hour classes are physical and earth science courses. I’ll comment on why this was so shocking later.

Next week is my last week, so I’ll have the rest of the summer to discuss random topics that have occurred to me throughout the ear.

Density Experiment

The last two weeks have been sort of like the ending to a movie. In Mr. Sowder’s class, the students have transitioned from learning physical science to earth science. The overall objective of the last unit of the semester is to help the students discover why the earth is shaped the way it is and why various formations exist on the earth’s surface. The students spent time plotting marks on a globe that represented earthquakes and volcano eruptions over the last 30 years. Mr. Sowder and I decided that I would lead a lab demonstration that explained the process of convective currents. Mr. Sowder would then take the information about convective currents and connect it with the theory of plate tectonics.

This assignment was perhaps my greatest challenge of the year. Earlier I had done presentations on college, or lectures on electricity, but I’d yet to lead a full-fledge lab. Furthermore, I was not entirely familiar with convective currents or plate tectonics. I know that this project would require a significant amount of research on my part. To make a long story short, I used several websites to get a food understanding of these concepts. Then, I found a few good activities that the class could do. From there, I constructed my lesson plan and crossed my fingers.

Mr. Sowder gave me two days to complete the lesson plan and I agreed to come in and do the lesson for his second hour (in addition to the fourth hour class which I normally visit). After researching convection currents, I thought it would be important to the students to have an understanding of density first. I began the lecture by explaining the terms mass, volume and density and showing how they were related. We did a few examples, but I wasn’t completely sure how well the class understood the concept. To explore density a little bit more, I began to do some demonstrations. I filled three cups with water, 91% rubbing alcohol, and vegetable oil. We then observed what happened when we put ice, wood, and aluminum in each cup. Much to the surprise of the class, the ice sank in the rubbing alcohol and kind of sank in the vegetable oil. The wood floated in all three and the aluminum sank in all three. Based of these observations and a table of densities, we walked through the steps of understanding that lower density materials float whereas higher density materials sink. The students absolutely loved this part of the class. They were very interested in seeing what would happen with the different solids in each fluid. I don’t think any students had seen ice sink before and I felt that was the key part to get them hooked on the day’s activity.

After establishing the basic concept of density, I asked the class to predict what would happen if we mixed alcohol, vegetable oil ad rubbing alcohol. Through lots of guessing, we made a prediction using the known densities of each species. I added food coloring to the rubbing alcohol in order to make it distinguishable from the water. The experiment worked nicely and the students were pleased to see their predictions come true.

Tune in next time to hear how the second day worked with the convective currents experiment.