Observing Osmosis in Gummi Bears

Observing Osmosis in Gummi Bears

I. Introduction

a. background information: Use the space below to define the following terms: diffusion, hypertonic, hypotonic, isotonic, dynamic equilibrium, osmosis, solute, solvent, passive transport.

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b. purpose: investigate the movement of water into and out of a Gummi bear

c. hypothesis: Use the following words: if, then, and so to write a hypothesis predicting the movement of water into or out of a gummi bear placed in pure water, tap water and salt water. Your hypothesis will be 3 sentences. One of them has been done for you.

If the gummi bear is placed in pure water, then the concentration of water is higher, lower than the concentration of water in the Gummi bear and so water will move into, out of the gummi bear resulting in a gain, loss of mass and volume.

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II. Materials and Experiment

a. materials: As you conduct the experiment write down all the materials you are using.

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b. Experiment

1. Obtain 3 Gummi bears of the same color. Obtain 3 small cups. Use a sharpie to fill in the blanks on the yellow data sheet.

2. labelthe three cups as follows:

• Pure water
• Tap water
• Salt water

Complete steps 3 – 6 for each of your three bears

3. measure your bears in cm.

• height (top to bottom)
• Width (side to side at widest point)
• depth (front to back at biggest point)

4. measure the mass of your bear.

5. Record it in the initial data portion of your data table and on the yellow data sheet. Use sharpie for the yellow sheet and black ink ballpoint pen for your data table. Calculate initial volume and density. Record on your data table in black ink ballpoint pen.

6. place your bear in the cup and cover the bear with the appropriate solution

7. Allow to sit for approx. 48 hours

9. Use a fork to catch the bear and scoop to the waxed paper. Without picking up the bear, measure height, width, and depth. Carry the bear on the waxed paper over to the scale and place paper and bear on the scale to mass it and and enter the data in the final data portion of your data table.

10. Calculate final volume and density and % change in volume and density.

11. Enter your data in the class data table and when every group has entered their data, record class data in the last 3 columns.

IV. Data:

a. Calculations:

Show your calculations in your notebook. Use these formulas

Approximate Volume = length X width X height (unit is cm3) (cm3 = ml)

Density = Mass/volume (unit is g/ml)

% change mass = [(final mass – initial mass)/initial mass] X 100

% change in volume = [(final volume – initial volume)/initial volume] X 100

% change in density = = [(final density– initial density)/initial density] X 100

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b. Data table – Give your data tables titles. Make sure they are filled in using black ballpoint pen

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c. graph. – present % change in mass and density in the three bears for both individual and class data. You can do this in one or two graphs.

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V. Conclusion

Write a paragraph that

• summarizes how the data compares with your initial hypothesis, how individual data compares with class data.
• Explains the differences between the bears in the three solutions.
• Discusses sources (more than 1!!!) of error. What went wrong? What might have made your data less-than-perfect?
• Explores further study – what else would you be interested in trying that was not a part of the original set up.

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IV. Analysis questions.

1. What accounts for the difference between your individual data and that of the class average? Why might it be different?

2. Using the term DIFFUSION, HYPERTONIC AND ISOTONIC explain what happened to the bear in the distilled water.

3. Why is % change in mass a better comparative measure than just change in mass?

4.
Tonicity / ______/ ______/ ______
Initial Data / Final Data
Gummi bear solution / Height / Width / Depth / Mass / Volume / Density / Height / Width / Depth / Mass / Volume / density
Pure water
Tap water
Salt water
Individual data / Class data
Solution / % change in mass / % change in volume / % change in density / Solution / % change in mass / % change in volume / % change in density
Pure water / Pure water
Tap water / Tap water
Salt water / Salt water
Your names ______, ______, ______
Your class period: ______
Solution
: / Solution: / Solution:
Initial length______/ Initial length______/ Initial length______
Initial depth______/ Initial depth______/ Initial depth______
Initial width______/ Initial width______/ Initial width______
Initial mass______/ Initial mass______/ Initial mass______