SECTION ONE: Methods
Lab 1 – Diffusion and Osmosis can be broken down into four parts (A, B, C, and D).
Lab 1A – Diffusion In this exercise, we tested diffusion through dialysis tubing. This was done through a demo with the teacher, rather than individually in groups. First, a piece of 2.5cm dialysis tubing was obtained. Then one end was folded and clipped securely so that a solution poured into the bag would not leak out. Next, the other side of the bag was opened. For step two, a 15% glucose/1% starch solution was tested for the presence of glucose with Benedict’s, and we recorded the data in a table. Using more 15% glucose/1% starch solution, 15 mL was placed in the dialysis bag. The other end was tied, …show more content…
For each tube, we folded up the bottom end and tied it securely so that the solution would not spill. Approximately 15mL of 0.4 sucrose solution was poured into one tube, while 15mL of 0.6 sucrose solution was poured into the other. Using our fingers, we removed most of the air out of the tube, and tied off the other end of the bag with string. Sufficient space was left so that the contents could expand. Both bags were then rinsed off gently with distilled water to remove any sucrose solution spilled. Then the outside of the bags were blotted off and the initial mass of each bag was taken, and recorded in grams. Each bag was placed in a cup that was labeled to indicate molarity of the solution in the dialysis bag. Each cup was filled with enough distilled water for the dialysis tubing to be completely submerged. The cups were left to stand for 20 minutes. At the end of this time, both bags were removed from the water, blotted and weighed again. The mass of each bag was recorded. Unlike the procedure called for in the lab manual, only 10cm of dialysis tubing was used per solution, as opposed to 30cm. Also, each cup was only filled with enough distilled water to cover the tubing, rather than 250 mL or 2/3’s of the …show more content…
First, we obtained four carrot sticks per sucrose solution, totaling eight carrots. Each group of carrots was weighted together in order to determine their initial weight. The four carrots for 0.4M sucrose and the four carrots for 0.6M sucrose were weighed separately. Then we poured enough of the assigned solution into each cup so that it would be able to coat the carrots completely, and placed the carrots in the correct cups. The cups were labeled and covered with plastic wrap. Then they were left to stand overnight. In the original lab instructions, potato cores were supposed to be used, and part of the procedure involved cutting the cores. Because baby carrots were used, this step was omitted. Instead of using 100mL of sucrose solution, only enough was used so that the carrots were submerged.
Lab 1D – Calculation of Water Potential from Experimental Data
( ) = –iCRT
a) 0.4M sucrose
( ) =