Molar Potatoes

Molarity is technically defined as the amount of solute dissolved in any given solvent. Students begin learning this fundamental concept in chemistry, but it seems that the topic isn't truly driven home until AP Bio. Likely the biggest reason that students don't fully grasp the significance of the principle during chemistry is that their isn't a truly concrete scenario to which they can apply their newfound knowledge. In AP Bio, however, students are forced to think in molar concentrations as they struggle to figure out whether water is going to flow into or out of a cell. Molarity is central to the concept of water potential and water potential is the fundamental force driving osmosis.

Generally the first big lab that students complete in AP Biology is an investigation of the principles of osmosis and diffusion. Over the course of three days they look at the relationship between surface area and volume using brilliant pink, phenolphthalein jello. Investigate water potential using dialysis tubing and various solution pairs. For the culminating activity I provide students with 5 sucrose solutions. Each solution is dyed a different color and has a different molar concentration. The students are not privy to the concentration associated with each color. After being given cylinders of potato, students are asked to design an experiment to determine the concentration of each solution. I must commend this year's class, nearly every group was able to correctly order the solutions. Ok, I think that I am done with what appears to be a fairly lengthy introduction. So, without further words, let me introduce our weekly reporters. Giving you a rundown for the week of 9/3-9/6 is Senior Melissa Amador and Sophomore Shaun Tarraporwalla.

Mel Begins:

This week in AP Biology has been both a long one and a short one. On Monday we had no school, because it was Labor Day. On Tuesday we completed the osmosis and diffusion, by doing procedure 3. In procedure 3 we had to find the molarity of 5 substances using potatoes. On Wednesday we played Jeopardy to study for the cells test. It always helps to play Jeopardy before the test because it reviews every topic we've gone through in the chapter. On Thursday we took our cells test, while being timed as if we were taking the AP test. On Friday I was not in class because I was assisting with the American Red Cross Blood Drive being held in our school. From what my classmates have told me, on Friday they took the Thermodynamics and Free Energy quiz on the videos from the nights before, and they were given the opportunity to work on the quarter projects due in a couple of weeks.

Shaun Concludes:

So everyone it time to sum up what happened during the first week of September… For those of you who don’t know the Monday on first week of September is a holiday known as “labor day” we were given that day off!

So starting on Tuesday we all hobbled into school weary and disappointed that we now again had to start waking up early after our long weekend had ended. However we were all excited by the time it was 4th period, this was because on Tuesday we were going to finish our labs! The activity we did involved us trying to figure out the correct order in ascending morality of different colored sucrose solutions. We achieved this by determining the percent change of potatoes that we had placed into each solution. The class was overall mostly successful in determining the correct order.  

Then on Wednesday we played a round of jeopardy which contained questions that helped us study for the test, the team that failed to have the least number of points would then receive extra credit…. Anyways the main event of the week was the dreaded test, I can not speak very much on this due to the fact that as of now we have not received our results but I can hope that we all did well.  On Friday we started by taking a test on Thermodynamics and Free energy, however there was also a blood drive taking place thus a significant portion of the class was unable to attend class. Due to this dilemma we had a short review and discussion of Thermodynamics and Free energy, after which we were given time to work with our partners on our TED ED projects. 


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