Osmosis Egg Lab

 

The Effect of the Movement of Solutions on the Mass of Decalcified Eggs

 

Question ~
How will the movement of water affect the mass of decalcified eggs if left in various solutions (distilled, 5% salt and 15% salt water) for two 15-minute trials?

 

Hypothesis ~
If three decalcified eggs are soaked in various solutions for two 15-minute trials, then the mass of the distilled water egg won’t change because its isotonic, the 5% salt water egg will decrease because its hypertonic, and the 15% salt water egg will decrease even more because its the most hypertonic.

 

Background ~
This experiment helps to study and give a visual representation of how osmosis affects the mass of animal cells, which is represented by decalcified eggs. Osmosis is a form of passive transport and diffusion concerning water molecules that moves from low to high concentration. This process was first discovered by Jean-Antoine Nollet in 1748. The word osmosis comes from “endosmose” and “exosmose”, which were coined by the French physician Rene Joachim Henri Dutrochet. When a solution is hypotonic, the water will flow into the cell, and when it is hypertonic it will flow out of the cell, and isotonic solutions maintain an equal rate of diffusion in and out of the cell. This topic is important because it can lead to future genetic, medical and agricultural advancements where humans and animals can be made more adaptable to internal changes in dynamic equilibrium.

Over 250 million years ago, the first land-dwelling reptile egg was created with a tough and leathery shell that protected it from possible fatal water loss. Today, chicken egg shells have approximately 17,000 pores on their surface which are constantly absorbing molecules. Decalcified is defined as being stripped of lime or bone; in this case, lacking an egg shell. All that is left to decalcified eggs is a semi-permeable membrane, which is used to represent an animal cell’s membrane. It is already known that plant cells use their cell walls to fight against plasmolysis and cytolysis, but how animal cells react to hypertonic and hypotonic solutions is still being explored because they do not have any defense mechanism like a plant cell does.

 

Procedure ~
1. Thoroughly wash hands
2. Acquire materials and set up at a clean  and unoccupied station.
3. Place a dry weighing boat on the electric balance and click on the zero button. Then, gently place the first egg on it and record its mass (grams) in a data table. Repeat for other two eggs.
4. Pour exactly 150mL of the solutions into their separate beakers. Using the Sharpie and tape, label the beakers accordingly: Distilled water, 5% salt, and 15% salt water.
5. Have all three team members carefully place an egg on their spoon. Slowly  and simultaneously lower them into their designated beakers. Start the timer at 15 minutes counting down.
6. Allow eggs to sit in their solutions; wash spoons during this time and clean up any mess.
7. After 15 minutes, gently spoon out the eggs and use the dry weighing boats and balance to find the mass again (record in the data table).
8. Repeat steps 5 – 7 one more time for a second trial and find the averages for each egg.
9. Clean the station, return materials, and wash hands thoroughly.

 

Variables ~

Independent: Each type of solution (distilled, 5% salt, and 15% salt water).
Dependent: The mass of the eggs after soaking in their assigned solutions.

Constants:
Same type of egg, amount of solution (150 mL), same weighing boats and balances, timer and time given for trials.

Control:
The distilled water solution.

 

Materials Available:

  1. Three decalcified eggs per group
  2. Distilled water, 5% salt water, 15% salt water (you will use 150 mL of each solution)
  3. Up to three 250mL beakers per group
  4. Masking tape
  5. Spoon
  6. Sharpies
  7. Weighing boats
  8. Balance
  9. Chromebooks/Mac Airs
  10. One class period to complete lab

 

Data Table

Control 5% salt water 15% salt water
0 minutes 92.09 91.06 91.91
15 minutes 83.36 89.92 87.82
30 minutes 82.41 87.29 86.08

 

Conclusion ~

The original hypothesis states: If three decalcified eggs are soaked in various solutions for two 15-minute trials, then the mass of the distilled water egg won’t change because its isotonic, the 5% salt water egg will decrease because its hypertonic, and the 15% salt water egg will decrease even more because its the most hypertonic. In answer to the question, soaking in these solutions made the decalcified eggs shrink; the solutions moved across the semi-permeable membrane from low to high concentration, from inside to outside of the egg. The hypothesis was incorrect because all of the solutions had hypertonic effects on the eggs. The distilled water egg changed the most by an average of  9.205 grams; the 15% distilled water egg changed second-most by an average of – 2.96 grams; the 5% salt water egg changed the least by an average of -2.455 grams. These results seem to be inaccurate, possibly because previous classes had handled the eggs and thus they had a lower salt solution inside than they had started out with. This experiment is an example of passive transport (osmosis to be exact) because it used no energy. Salt is similar to the ions in facilitated diffusion and active transport, but osmosis is opposite from those types of transport because they concern energy, not water, and go from high to low concentration. Errors in this experiment could have been not zeroing the scale perfectly, sanitizing the equipment and work station poorly, and using eggs that had been handled by earlier classes. If this experiment is to be repeated, one should use freshly decalcified eggs, sanitize the equipment properly and have a 24 hour trial with two sets of eggs (for two trials) to allow more time for diffusion and to have more accurate results. To learn more on this topic, one should repeat this experiment with the egg shells intact to examine how plant cells and their cell walls react to osmosis.

Works Cited

“Shell Eggs from Farm to Table | USDA Food Safety and Inspection Service.” USDA Food Safety and Inspection Service Home. Web. 03 Nov. 2011. http://www.fsis.usda.gov/factsheets/focus_on_shell_eggs/.

 

“Egg Facts.” Egg Nutrition Center. Web. 07 Nov. 2011. http://www.eggnutritioncenter.org/page/egg-facts.

 

“Decalcified | Define Decalcified at Dictionary.com.” Dictionary.com | Find the Meanings and Definitions of Words at Dictionary.com. Web. 09 Nov. 2011. http://dictionary.reference.com/browse/decalcified.

 

“Osmosis: Facts, Discussion Forum, and Encyclopedia Article.” AbsoluteAstronomy.com. Web. 10 Nov. 2011. <http://www.absoluteastronomy.com/topics/Osmosis>.


One thought on “Osmosis Egg Lab

  1. T: 5
    WE: 4

    SP: excellent background and citations; 5

    DC: need qualitative data; graph is good except it really should be a line graph; movement of water molecules is from high to low and the water movement is dependent on what the concentration of salt solution is outside of the egg; 4

    AS: 4

    Transport Standard 2: 4

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