Science in the Park - Egg Science

This week's edition of "Science in the Park" featured "naked eggs"!  Naked eggs are eggs that have been soaked in vinegar for a few days dissolving the hard outside shell to reveal the rubber-like insides.  Since the eggs (although very cool) didn't take much time - we did a repeat experiment of "elephant toothpaste" that definitely "wows" the kids.

Naked Eggs

Preparation

1. Soak 2 dozen eggs in vinegar for 4 days (no - it won't smell like anything other than vinegar). 
2. On the night before, gently rub off the remaining "white material" to reveal the naked egg.  I found it easiest to do this under running water.  I started with 24 eggs, but I only got 14 naked eggs (I broke the rest). 
3. After rubbing off the white material, put the eggs back in fresh vinegar and by the next morning, anything I couldn't rub off had come off by itself. 

Experimenting

Material List:

• eggs soaked in vinegar (and transported in the vinegar)
• gloves for the kids so they can touch the eggs
• food coloring for coloring the eggs
• recycled yogurt cups for holding the egg
   

Examination

Most of the experiment is just the egg itself - so start off by examining the egg.

Q&A Conversation Starters:

• Ask: What is missing from the eggs?  When the answer "shell" is given, state that the eggs were put in vinegar for a long time to dissolve the shell.  <The science: the shell and the vinegar have an acid/base reaction!  The shell is made of calcium carbonate and the vinegar breaks it down into calcium and carbon dioxide which are the bubbles that form on top>
• Ask: If there isn't a shell...then what is holding the egg together?  Mention that when you crack an egg, the egg is runny and liquidity.  The answer is that an egg actually has two membranes that stick together to look like one and then the egg shell is on top of that!  <The science: these semi-permissible layers are called the "outer shell membrane" and the "inner shell membrane" - very creative names - and they are made partly of keratin (the same as your fingernails!) >

Experimentation

Next we colored the eggs by putting the eggs in water with food coloring. After a few minutes the egg turns the same color as the water.

 

Conversation Starters:

• Osmosis!  Talk about how the water traveled from the cup into the egg by using osmosis to get into the egg and since the water was colored - when the water went into the egg, it turn the egg the same color as the water!
• Older kids : talk about how the egg is composed of 90% water and so when it is placed in a cup filled with 100% water - it wants to find its equilibrium meaning it wants to be the same inside the egg and outside the egg.  So that is why water travels into the egg via osmosis.

 

Ending

So - now what should you do with the naked egg...

• Some kids couldn't wait to smash it!  When you break the membrane you get a vinegary runny egg and a membrane in your hard!
• Some kids (mine!) wanted to take the egg home and let it sit for a few days outside of vinegar.  Then the egg becomes more like rubber and can be dropped and "bounced" a few inches off the ground. 
• You can also let it sit in the colored water overnight
• Or - you can soak in in corn syrup overnight to get a dehydrated egg!