AP Biology

Egg Osmosis

The naked egg experiment aims to show how the egg behaves inside different substances(hypotonic and hypertonic). We watched a video, and had the hypothesis that when the egg was placed into a hypotonic solution, the egg would shrink, and when placed into an hypertonic solution, the egg would swell. To start, we weighed the egg, then placed it into vinegar to dissolve the shell.

Prerequisite Information

Osmosis

Osmosis is the net movement of solvent molecules(water) across a selectively permeable membrane from an area of higher concentration to an area of lower concentration.

Hypotonic, Hypertonic, Isotonic

Hypotonic, Hypertonic, and Isotonic are terms used to describe the relation between a solution and an object placed inside of it.

Comparisons

Hypertonic solutions have more solute outside than inside the cell, which leads to water moving out of the cell to reach equilibrium.

Hypotonic solutions have less solute outside than inside the cell, which leads water to enter the cell to reach equilibrium.

Isotonic solutions have equal solute outside than inside, which leads to no net movement(equilibrium).

First Step - Weight(41g)

The egg weighed 41 grams at the start of our expiriment. We placed it into vinegar, and then waited 2 days for the shell to dissolve.

Post-Vinegar(53g)

The egg ballooned to 53g, an increase of about 30%. This is because the vinegar was hypotonic to the egg, which made the egg swell with water.

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Second Step

We then placed the egg into corn syurp, and waited another 2 days for the reaction to fully take place

Post-Corn Syurp(39g)

After the 2 day waiting period, we came back to find that the egg was shriveled, smaller than even the initial size. The weight was 39g, a decrease of about 25%. This was because the corn syrup was hypertonic to the egg, which made the egg shrink as the water entered the corn syrup.

Third Step(57g)

For the last step, we placed the egg into distilled water that had food coloring in it. Again, we had to wait 2 days for maximum effectiveness. Once we came back, the egg had again swelled, but was bigger than the first swell when placed in vinegar. It's final weight was 57g, an increase of 46% from the corn syrup and 40% from the initial weight.

Final Observations

Our hypothesis was correct, with the vinegar and distilled water making the egg swell, and the corn syurp making the egg shrink.

We also thought about why the egg was larger in the distilled water as compared to the egg in the vinegar, even though the mass of the egg to start was double the mass of the egg after corn syrup. We developed the hypothesis of because vinegar isn't completely water, that the cell needed to intake less water to become isotonic, as compared to the distilled water.

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