Experiments at the Children's Desk - Eggs-periment!

Wednesday, August 6, 2014

This was probably our grossest (in a good way!) experiment yet--and it didn't turn out exactly like the fabulous blog post we modeled it after, which can be found here. As always, we had a lot of fun and said the word "membrane" a lot that particular week.

The first stage of the experiment went smoothly--we placed two eggs in mason jars filled with vinegar. Our goal was to dissolve the shell of the egg and create semi-permeable membrane. This stage alone makes for an interesting experiment, because when you take the egg out after about 24 hours, you can bounce it! (Just a little, not as high or with as much intensity as a bouncy ball.)

Pictured here is one of our eggs in vinegar. The vinegar contains acetic acid, which breaks apart the solid calcium carbonate crystals that make up the eggshell. The calcium ions float free (calcium ions are atoms that are missing electrons), while the carbonate goes to make carbon dioxide—the bubbles that you see.

24 hours later, most of the eggshell was dissolved. We gently washed off any remaining bits and ended up with two bouncy eggs! Success! Now here's where the eggs-periment didn't go quite as planned...

Next, we put the eggs in two different solutions. The first egg was put into a jar of tap water with a pinch of red food coloring (to differentiate--and see if the membrane would absorb the color). The second jar contained sugar-water. However, we didn't follow a specific recipe to get the results we wanted. We simply made a sugar-water solution instead of measuring out the sugar and water to ensure saturation. That doesn't sound very scientific now, does it?! After searching the web, we found that other people used corn syrup or treacle in order to get the desired results.

 As you can see from the  Science Sparks post that we linked to, the egg in a sugar and water solution should absorb less water than the egg in water. However, we believe that our water was not saturated with enough sugar, and therefore both of our eggs were roughly the same size after a few days in their respective solutions (the weight of the eggs is unknown) because water was able to permeate through the membranes of both eggs at a similar rate.

We also attempted to poke the egg that had been in the water, hoping that water would start streaming from the hole. Perhaps the end of a thumbtack was a poor choice, as this is what we ended up with:

It is probably a good idea to use a thin needle instead!

While this experiment didn't turn out exactly like we planned, it was a lot of fun and comes highly recommended!

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