Investigation 4: Osmosis and Diffusion

Investigation 4: Osmosis and Diffusion
Procedure 1:  Surface Area and Cell Size
Brief experiment purpose and hypothesis: The purpose of this experiment was to discover how cell size and shape can affect a cell’s metabolic effectiveness - essentially, which can diffuse materials in and out at a faster rate. We predicted that a cell with the greatest surface area to volume ratio would be the most effective because it would have a larger area to bring out and in materials into a smaller section of volume.
General procedure with materials: Three cubic blocks of agar were cut out using a thin strip of hard plastic. One block had sides of 0.5 cm, another had sides of 1 cm, and the third had sides of 2 cm. Each agar block contained NaOH and the pH indicator dye phenolphthalein, turning the cube a bright purple. Once cut out, each block was placed in a separate petri dish filled with water. A video was taken to analyze which agar cube lost its coloring the fastest through diffusion.
Results & Conclusion:
Time Lapse Video: https://youtu.be/KrLB6v4oWDw
We realized that the smaller agar cubes would diffuse faster than the larger cubes. When the cube turns clear, it has completely diffused and this is seen through our time lapse video. We concluded that surface area does affect diffusion rates and that substances with a smaller surface area will diffuse faster than those with a larger surface area.

Procedure 2:  Modeling Diffusion and Osmosis
Materials:
  1. Distilled Water
  2. 1 M sucrose
  3. 1 M NaCl
  4. 1 M Glucose
  5. Cups
  6. Balances
  7. Timer / phone
  8. 20 cm-long dialysis tubing
Procedure:
  1. We first got 3 cups and filled each with different solutions (water, NaCl, sucrose). We got 3 dialysis tubes each filled with water and weighed it before letting it sit in the 3 different cups. Then we got one more cup and put NaCl in it but this time the dialysis tubing in the cup contained sucrose. After 12 minutes, we weighed the dialysis tubing of each solution to see if water went in/out or stayed the same. Then we calculated the percentage change in weight.
Results:












Procedure 3:  Observing Osmosis in Living Cells
Video: https://youtu.be/8JOF7Qu9hoY
Pictures and Results:
Through this experiment we were able to see the Elodea leaf contract as its cells went through osmosis. When we put the saltwater (NaCl) onto the leaf its cells contracted and this is seen through the amount of clearness seen within the cells of the elodea leaf. In the before picture it is fully green but after osmosis, its cells contract and they turn clear.




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