Behind the Scenes: In the Lab

My partner and I performed a lab about diffusion and osmosis not too long ago.  Here is each of the practices that were utilized in the lab:

Science Practice #1 “The student can use representatives and models to communicate scientific phenomena and solve scientific problems.”

• Science Practice 1 was utilized when we each had to create 3 dialysis-tubing bags to mimic a cell model. Each bag held a different solution; glucose, ovalbumin, and sucrose, and the solution was then placed inside of a few beakers each with a different paring of a solution to test the effects of concentration on diffusion.

Science Practice #2 “The students can use mathematics appropriately.”

• The next practice was used multiple times throughout the experiment. We had to calculate the percent change of the solutions by using this formula: final weight/ initial weight x 100. We also used our knowledge of water potential: = (water potential is the sum of solute [ -iCRT: ion, concentration, 0.0831, and temperature] and the pressure). Calculating the water potential indicates which way the water will flow and whether or not the dialysis bag will expand or shrink.

Science Practice #3 “The student can engage in scientific questioning to extend thinking or to guide investigations within the context of the AP course.”

• Science Practice 3 was used when we did another lab that required the use of potatoes to determine how to find out the molarity within each solution. In this lab, my partner and I had to come up with out idea on how to complete this ourselves and we proved to be successful when we put our two heads together.

Science Practice #4 “The student can plan and implement data collection strategies appropriate to a particular scientific question.”

• Then the next practice included gathering data for all aspects of the lab.  When we did the experiment with the dialysis tubing, we had to document things such as the mass of the solutions before and after the procedure, how much of each solution was inside of the bag and in the beaker, and what the conditions were for each of the solutions like factors such as temperature.

Science Practice #5 “The student can perform data analysis and evaluation of evidence.”

• Science Practice 5 was utilized in each of the labs we conducted throughout the week. Through the data that we collected, we came to the conclusion why osmosis or diffusion happened for each particular pairing of solutions.

Science Practice #6 “The student can work with scientific explanations and theories.”

• The next practice was in need when my partner and I had to explain why osmosis occurred in the potato lab, and as well as the dialysis lab. We figured that if the bag shrunk or if the potato weighed less, then the concentration must have been higher on the outside than on the inside of our cell model. The increase in mass in the potato helped us conclude that the solution had more molarity than one who had a loss of mass.

Science Practice #7 “The student is able to connect and relate knowledge across various scales, concepts and representations in and across domains.”

• By using Science Practice 7, my partner and I were able to make connections to what we had previously learned in class. In the cell model using phenolphthalein, we were able to see how the cell size affects diffusion. The bigger the cell, the longer it will take for molecules to diffuse throughout the cell, which then impacts how other molecules such as water and proteins are able to move through out a cell.  If cells aren’t able to work properly, then they will be of no use to our body.