Did you know you can study cells by studying eggs? We did it with a cool egg cell study. We are loving our Pandia Press Life Sciences curriculum and have been doing a unit study on cells and as part of that study we examined raw eggs to learn about their parts. This was a great introduction into the concept of the cell, but we decided to take our study of the egg up a notch. Check out our egg cell study!
To start off our unit study we did the worksheet and associated experiment in our Pandia Life Sciences textbook. We read about cells and how they make up all living things. Then we cracked open a raw egg and looked for the various parts of the egg and labeled them on the worksheet.
But we wanted something more. Way more. So… our first step was to make our eggs naked by removing the shell. We did this by placing our raw eggs in vinegar for 48 hours. The reaction was instant!
Bubbles started forming all over the shell as our chemical reaction began. Carbon dioxide bubbles are formed by the vinegar reacting to the calcium in the egg shell. You will end up with a foam on top and eventually you will have only liquid water left. In one batch of our eggs we found we had to replace our vinegar after 24 hours because it had all turned to water and our shell had not completely dissolved yet.
Here is the chemical reaction if you are interested:
CaCO3 + 2 HC2H3O2 → Ca(C2H3O2)2 + H2O + CO2
To break this down you have:
Egg Shell + Vinegar → Foam Floaties + Liquid Water + Carbon Dioxide Bubbles
To carry our experiment even further we added a few drops of food colouring to our vinegar in order to dye the eggs. This makes for some really cool looking naked eggs plus it will help with the egg study later on.
Once the eggs are naked handle them very carefully. The membrane is quite thin and will break quite easily. If you hold the egg over a bright flashlight you can see the yolk inside. Move the egg around and you can see the yolk floating about.
After you are all finished checking out the eggs with a flashlight (and marveling over the fact you are holding a raw egg with no shell… DON’T SQUEEZE!), take the egg and place it on a plate. Very carefully poke it with a knife or toothpick to pop it open.
The dye travels through the membrane into the egg white, but a special membrane around the yolk stops the dye from traveling into the yolk. A great visual for permeability and osmosis.
But closer inspection shows that some very special parts of our egg have taken in quite a lot of the dye. The chalaza, stringy bits on either side of the yolk that help to hold it in place, and the blastodisc, a circle in the middle of the yolk, this is where the sperm enters to fertilize the egg and is the nucleus of the egg (just like a cell!).
Dying the egg makes it much easier to see all these parts of the egg and start a study into cells and their structures.
This was such a fun way of exploring cells, eggs and chemistry (a favourite around here). I hope your little scientists enjoy our egg cell study as well.