Hot Potato Lab

This year, my school is teaching our high school Biology classes through College Board's Pre-AP program. Even my Honors Biology class is going through Pre-AP Biology. One of the concepts that I have to teach with this curriculum that I haven't before at this level is Surface Area to Volume ratio in the context of how it plays a role in the size of cells. 

I teach this in AP Biology and we do the Surface Area to Volume diffusion lab using agar with phenolphthalein and sodium hydroxide and soak different sized cubes in dilute hydrochloric acid. I love this lab, but don't want to do it with my honors bio students, since they would do it again in AP Bio. So of course, I did a google search and found this hot potato inquiry lab. 

From the lab linked above (which is the answer key to the lab), I put together a google doc for my students to work with. Here is the link to that lab document.

I loved this lab, and I'll be keeping it in my curriculum for sure. Like many of the labs I do with students, I was so busy helping them trouble shoot and prepare that I forgot to take pictures. 

My students liked this lab because they got to use our Vernier temperature probes, and they love to use the probes. Since they used probes, students could just poke the probe right into the potato. They could also see through graphing the data what was happening with the rate of temperature loss. (But maybe this made me more excited than them.)

Here are some tips for the lab. I forgot to bring a crockpot to keep the potatoes hot during the day and I didn't cook them ahead of time. I have an incubator in my room whose maximum temperature is 60°C. In the morning, I put them in the incubator. Right before this last block class I put the potatoes in my classroom microwave for 5 minutes to make sure they were cooked all the way (soft), then put them back into the incubator until students needed them. The key is that they start with the potatoes hot. Even just being in the 60°C incubator was enough to keep the potatoes warm enough for the lab. 

None of the potatoes started at the same temperature, but that didn't matter since we were looking at the rate of temperature change for each of the potatoes.  Students used Google Sheets to collect their data and then graphed a scatter plot, added trend lines and the equation of the trend line. We then discussed how the slope of the trend line is the rate of heat loss from each potato.