One of our favorite science experiments is the Naked Egg experiment. This is one of the first chemistry experiments we ever did, and we love it! The result can be a bit messy, but it’s a lot of fun! When I had my niece over for Fall break, we tried it again. Only this time, we gave it a bit of a Halloween twist…
Wide mouth jar (about the size of a far of pasta/marinara sauce)
Large bottle of white vinegar
(Optional) Green food coloring
1. Carefully place your egg into your jar. Pour in your white vinegar, adding enough to fully submerge your egg.
2. Add several drops of green coloring and carefully stir it in.
3. Put your jar in the refrigerator and wait. You’ll need to wait approximately 48 hours for this demonstration to take effect. After the first 24 hours, carefully pour the old vinegar out, making sure not to damage the egg inside. Pour in a fresh batch of vinegar (make sure to replenish your food coloring as well) and put it back in the fridge for another 24 hours.
4. After your 48 hours are up, carefully dump out the vinegar, and check out your goblin egg! (Make sure to take it outside or hold it over a sink!)
Note: During the 48 hour waiting period, make sure to periodically check on your egg! The developments that occur over this time frame are really interesting, and will be sure to provoke a discussion about what’s going on! Speaking of which…
One of the first things we notice when we do the naked egg experiment, is that we quickly see a lot of bubble appear on the egg! Within just a few minutes, we see small bubbles rise to the surface of the vinegar. Within 24 hours, the entire egg is covered in them! What’s going on?
Vinegar is an acetic acid that has a pH of 2.4, meaning it has a high acidity (although store bought vinegar is usually only 5% vinegar mixed with water)! The shell of the egg is made of calcium carbonate, which has a pH of 9.2, meaning it is more alkaline (basic). As with baking soda and vinegar, when you mix these two together, you can get quite a reaction!
The bubbles form because the vinegar breaks the calcium apart from the carbon and oxygen molecules. The result is a carbon dioxide gas that forms on the egg and rises to the surface. You’ll also notice a film begin to form on the surface of the vinegar. This is what is left of the calcium from the egg shell!
Why is the egg bigger?
When the egg shell dissolved, it left behind a thick membrane. This membrane acts as an extra defense against bacteria and other harmful organisms. When the egg is soaking in the vinegar, some of the vinegar is able to pass through the membrane and enter the egg. The egg effectively absorbs some of this vinegar! This passing of one substance through a membrane and into another substance is called osmosis.
We wanted to see what would happen if we added some variables into our experiment. We soaked one egg in water for 48 hours, another in vinegar for 48 hours, and another in whole milk for 48 hours. The goal was two fold: to see if the calcium would strengthen the egg shell, and to see if the green food coloring would still be able to permeate the egg.
Unfortunately, we didn’t have a way to actually measure whether the milk added any calcium to the egg! The next time we try this, we’ll have to add a kitchen scale to our supply list so we can accurately determine our results. As for the second part of our question, the shell did prevent the molecules from the food coloring from passing through, leaving our egg perfectly safe from any green invaders.
Finally, since we had our egg sitting in vinegar, and we had been spending a bit of time talking about the chemical reactions of acids and bases, my daughter and niece thought it would be a good idea to throw some baking soda on to our goblin egg!
They wanted to know if the added chemical reaction would weaken the egg and cause it to break open on the plate. After adding several rounds of baking soda and vinegar to the already dissolved egg, it surprised us all by still standing strong! That inner membrane is surprisingly tough!
However, as with every time we’ve done this experiment, it doesn’t take long before something happens to that egg to break it open. In previous years, it has been bounced (it actually does bounce a fair bit if you drop it from about 4 inches off the ground), thrown, and squished. This time, the girls decided to toss it back and forth to each other, resulting in a predictable eggsplosion of vinegar and egg!
Surprisingly, the yolk was still yellow! Even though the egg had absorbed quite a bit of vinegar, there was only a small amount of green within the egg white, and that was primarily located on the surface of the membrane itself. The nucleus of the egg was completely protected from the green food coloring!
All in all, we had a fantastic time making our Goblin Eggs. It was a perfect way to spend Fall Break with the kids! With our Halloween twist, it was creepy, gross, and a lot of fun. It was a smashing success!