So now that we know how to make a NAKED egg (giggle, giggle) we can investigate osmosis which is the movement of water through a membrane. It’s best if you have 4 naked eggs. If you don’t know how to make a Naked Egg click here.
Here’s what you need to get started:
- Naked Eggs (We used 4 and 1 broke)
- Food coloring
- Corn Syrup
- Clear Jars/Cups
I helped the superheroes take the eggs out of the vinegar that the eggs had been soaking in (to dissolve the shells) and rinsed the outside with water. Next, we gently placed them back in the clear jars. Unfortunately, one broke (our salt water egg) so we were left with 3 naked eggs. We poured water over one egg, water with green food coloring over the 2nd egg and corn syrup over the last egg. And then we let them sit overnight.
Because the eggs had absorbed water from the vinegar solution, the egg in the corn syrup began to float (water is less dense than corn syrup so the egg floated a bit). This will not affect your results.
After 2 days of soaking, the eggs looked like this (from the top):
You can see the water egg has turned white again and has gotten bigger. The egg in the green water has turned green. Interestingly, the egg in the corn syrup has begun to shrivel up and the yolk is very visible. We took the eggs out of the jars to investigate them a bit more.
I asked the superheroes what they think happened. The green egg was the easiest for them to understand. My little superheroes were pretty impressed with the shriveled egg. I let them hold the eggs and feel the differences between the eggs.
The Science behind the Experiment:
What is going on with the naked eggs?
Once the shell disappears, a permeable membrane remains. Permeable means that substances can penetrate (or diffuse into) the membrane, such as water. This process is called osmosis, the diffusion of water. Water tends to move from areas of higher water content to lesser water content until the water content on each side of the membrane is equalized.
In the case of the eggs in water and green water, the water content inside the eggs was lower than that outside and so the water moved into the eggs and made them bigger. The membrane to the egg is also permeable to food coloring so that is why the egg in green water turned green.
In the case of the egg in corn syrup, the water content of corn syrup is lower than that inside the egg so water moved out of the egg and into the corn syrup. This caused the egg to shrivel up. If our salt water egg had not broken, what do you think might have happened to the egg? Test it out to see if your guess (hypothesis) is correct!
Many secondary teachers use this experiment to demonstrate how the membranes inside of our cells work. Our cell membranes are semi-permeable which means some substance can penetrate the membrane and others cannot. This characteristic is vital to how materials move in out of out cells and our bodies.
Follow this link for more details about this experiment: