Agar Lab. Sophie, Regan, Libby

Transcription

1 Agar Lab Sophie, Regan, Libby

2 Agar Lab: Our Data Independent variable: Width of the agar Levels of IV Dependent variable: Time it takes for NaOH to diffuse (seconds) 2mm, 4mm, and 8mm # of trials 3 constants 3 drops of NaOH 1 cm hight 1 cm length Drops placed in the middle of the agar block

3 Data Cube Trial Surface Area Time of diffuse with 2mm width Volume 2 mm 2.8 cm 2.2 cm mm 3.6 cm 2.4 cm 3 9 Time of diffuse with 4mm width SA to V 6mm 4.4 cm 2.6 cm Time of diffuse with 6mm width 1 36 sec 21 sec 27 sec 2 25 sec 30 sec 29 sec 3 16 sec 48 sec 58 sec Cube Trial Trial Trial Average Surface Area Volume Cube 6 cm 2 1 cm 3 6 Triangular prism Triangular prism SA to V 7.24 cm 2 1 cm Average

4 Data Analysis The data on the previous slide shows proves that as the surface area to volume ratio decreases the time required for the agar to diffuse increases. For the triangular prism and cube they both had the same volume, but the cube had a smaller surface area. Since the cube had a smaller surface area it took a longer time to diffuse than the triangular prism. This is caused because a greater surface area is needed to diffuse the volume. When the volume is increased it takes longer to diffuse, because there is a smaller space for molecules to enter and leave.

5 Potato Core Lab Independent variable: Concentration of sugar Dependent variable: % Change in Mass of potato core Levels of IV 5 # of trials 43 constants 4 cm long potato core same room temperature type of potato amount of solution in cup

6 % Change in Mass of Potato Cores Class Average Green purple yellow clear red brown

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8 Results C=.2653 The water potential of the potato was The negative Ψ value indicates that water tends to move out of the cell, meaning that potato cells are generally hypotonic. The average data found a negative Ψ value when the potato cores were placed in the yellow, clear, red, and brown liquids. Through a process called osmosis, water moves from areas of higher water concentrations to areas of lower concentrations. If water was moving out of the potato cells within these solutions, it means that there was a lower concentration of water and a higher concentration of solute within these solutions, in comparison to the potato cores. Through this data, we are therefore able to conclude that these solutions are hypertonic to the potato cells. Our data found positive average Ψ values when the potato cores were placed within the green and purple solutions, meaning water had a tendency to enter the potato cells. These solutions had higher concentrations of water and lower concentrations of solute in comparison to the potato cores, making them hypotonic solutions.

9 Dialysis Tube Lab

10 % Change in Dialysis Tube Mass Sucrose (outside) NaCl Sucrose (inside) NaCl Glucose Egg White Water The positive values for sucrose indicate that the liquid is moving inside the dialysis tube, indicating a hypotonic solution. The negative value for glucose and ovalbumin indicate that liquid is leaving the dialysis tube which creates a hypertonic solution. Glucose Egg White Water

11 Analysis of data The data should have shown that sucrose molecules, glucose molecules and ovalbumin molecules are too large and can not pass through the dialysis tubing pores. This would be shown by a negative value for the % change. These will all create a hypotonic environment because there is more solute inside the dialysis tube then outside of it. The NaCl and Glucose should have created a hypertonic solution, which would be indicated by a positive value. The water should have created an isotonic solution because the concentrations would have been equal on the outside and inside of the tube.

12 Possible Errors If several of the tubes were not tied tight enough, this would release the water and solutes from within the tube without requiring it to diffuse across the membrane. The surface areas of the dialysis tube membranes varied depending on where they were tied off, which affected the rate of diffusion both in and out of it. The data was also added to the spreadsheet in a confusing manner that make the results unclear. The lack of trials for each combination also results in incorrect data.