Osmosis Egg Lab Part 1

This week we had to implement a structured inquiry lesson. Since I am currently substituting I have been working with one of the 5th grade teachers at the school. The students had been learning about plant and animal cells. I thought it would be fun for the students to see how the cell membrane works and explore osmosis. The first day we watched the BrainPop video on Passive transport found here http://www.brainpop.com/science/cellularlifeandgenetics/passivetransport/.

I used the experiment listed as my demonstration to give the students some knowledge about osmosis. The experiment used peeled carrots; one carrot was placed in a bowl of water and the other was placed in a bowl of salt water. A third carrot was left out as a control. We checked the status of the carrots at the end of class, but then left them overnight. The carrot in the water became stiff and was hard to bend because the water diffused into the carrots cells. At the same time the carrot in the salt water the water diffused out of the cells and the carrot became soft and very bendable.

Now that the students were armed with some background information we could work on our osmosis lab. The first step was preparing the eggs- to do so eggs were placed in a cup and covered with vinegar. The vinegar produces a chemical reaction with the shell and leaving the egg surrounded by the membrane. The students massed the eggs and predicted what they thought would happen to the eggs. The eggs were then placed in various solutions including:

Distilled Water

Colored Distilled Water

Salt Water

Karo Syrup

and

Molasses

The eggs were left overnight. The next day we observed and massed the eggs. All of the eggs in the water solutions gained mass while the eggs in the sugary solutions lost mass. Here you can see the eggs that were in the molasses and the Karo syrup lost mass and left dents in the eggs.

The purpose of using the colored water was the show the students that it is the water that is entering the egg, they compared it to Easter egg dying as that is what it looks like.



Here is one last shot of a very bloated egg.

After all the observations had been made we popped the membranes to see what would happen. Those that were in the water solutions produced geysers as all the water came shooting out. The eggs in the sugary solutions did not do much since the water had diffused out of the egg. Unfortunately we ran out of time to finish up their calculations and conclusions so we will continue our discussion this week and give them time to create their posters demonstrating how osmosis works. Examples of student work will follow in a few days. The students have been very excited to do some hands on activities and the teacher would like me to continue to work with her on new ideas and she was ecstatic to see how her students responded to this activity.

The lab was initially found here:

Bilash, B. & Shields, M. (2001). A demo a day- Biology. Flinn Scientific.

Some other references for the lab came from one of my favorite sites The Science Spot found here

http://sciencespot.net/Pages/classbio.html#Anchor-eggs

Recently on the NSTA listserv someone was looking for kitchen science lessons and someone else shared this sitehttp://www.exploratorium.edu/cooking/index.html