Around Easter each year, most of us find ourselves suddenly charmed by that humble breakfast staple: the egg. Nestled under shrubbery and snuggling tulips in flower beds, hidden eggs await Easter egg hunts. Dotted, dipped, and dyed, colored Easter eggs adopt an artistic air. But the following egg activities are not art, but science. Learn the chemistry concepts of dissolving and density with a foldable egg project and a floating egg experiment.
Foldable Egg Science Project
Here’s a neat trick: dissolve an egg’s shell to find the thin egg-shaped inside layer and discover how strong and flexible it is when you fold it up and then inflate it with air like a balloon!
Parents: Please note that the preparation for this experiment requires careful handling of a raw egg. We strongly recommend that you prepare steps 1-5 of the project in advance. You can view a demonstration of the project first.
What You Need:
- raw egg (at room temperature)
- drinking straw
- white vinegar
- a glass
- baby powder (or cornstarch)
- an adult to do steps 1-5
What You Do:
- The first step is to blow the contents out of a raw egg. Hold the egg over a bowl and use a thumbtack to pierce a small hole in the pointed end and a larger hole in the other end of the egg. (To enlarge a hole, make several small holes close together and use the tack to gently break away the shell between them.) Hold the egg very gently to make sure you don’t crack it!
- Use a skewer or unfolded paperclip to carefully break up the yolk inside of the egg.
- Hold a drinking straw over the smaller hole and blow through the opposite end of the straw. The pressure from the air moving through the straw will push the egg contents out into the bowl.
- Run a little water inside the egg and shake it out. Use the straw again to blow out any remaining water.
- Place the egg shell in a glass and add enough vinegar to cover the egg. Using your fingers or a pair of tongs, gently hold the egg under the liquid until the air escapes and most of the egg shell stays below the surface (this may take several minutes).
- Leave the egg in the vinegar for several days until the shell begins to break down (can take up to 10 days).
- When the shell has started to break away, you will see a flexible egg shaped layer inside—this is the egg membrane. Once the egg shell has completely dissolved, remove the membrane from the glass of vinegar.
- Rinse the membrane in water and gently squeeze it to remove the water from inside. Pat it dry with a paper towel.
- Toss the egg membrane back and forth between your hands like a ball. It might take some patience, but you should start to see parts of the membrane filling with air. Continue tossing until the whole thing has inflated light a balloon. (You can slowly and gently pull the sides apart to separate them enough to allow air in if you need to.)
- Once it has inflated, sprinkle a little baby powder all over the outside. Try to get some powder inside as well as it will prevent the sides from sticking together and help the egg inflate more easily next time.
- Set the powder-coated inflated egg on the palm of your hand and press the air out with your fingers. Fold the egg in half several times and pinch it slightly so it stays folded, then toss it between your hands again and watch it reinflate! This process of folding and tossing can be repeated several times until the egg membrane dries out and won’t inflate.
Vinegar contains an acid (called acetic acid) that can make certain substances break down more quickly. When something dissolves, it breaks into very tiny pieces and mixes with a liquid. You can easily demonstrate dissolving by placing a sugar cube into a cup of hot water and stirring. The sugar cube disappears as the sugar dissolves into the water. An egg shell is made up of calcium carbonate, which dissolves quite easily in acetic acid (vinegar). The vinegar eventually dissolved the entire shell away, leaving behind a thin, flexible egg-shaped membrane. The membrane is a very special part of an egg—it is what protects a baby chick as it develops inside a fertilized egg. Because its job is to protect a chick as it grows, the membrane is actually quite strong, thanks to the fact that it contains keratin, which is the same protein that makes your hair strong!
Note: we used a brown egg in the photos, which is why there is strange brown stuff floating in the glass of vinegar. White and brown eggs will both work for this experiment.
What You Need:
- two raw eggs
- two glasses or jars (similar size and shape)
What You Do:
- Fill each glass half full of tap water.
- Using a spoon, gently set one egg into each glass of water.
- Add 3 tablespoons of salt to one glass and stir it being careful of the egg. There should still be some salt at the bottom of the glass that won’t dissolve. If not, add another tablespoon of salt. As the salt mixes with the water, the egg should rise higher in the water until part of the egg is above the surface of the salty water! If this doesn’t happen, add more salt a tablespoonful at a time and stir until the egg begins to float.
A normal egg sinks in plain water because the egg is more dense than the water. Density is a measure of how solid something is. All things are made up of tiny particles called molecules. If the molecules inside an object are very close together, the item is solid, or dense. If the molecules are farther away from each other, the object is less dense, or less solid. (An example of a very dense item is a penny. A cork is less dense.) When enough salt is added to water, the density of the water changes and becomes more dense than the egg, causing it to float up towards the surface of the water!
To take this experiment a step further, you can remove the egg from the first glass and use a dropper or a spoon for slowly add the plain water from the first glass on top of the saltwater in the second glass. The key is to add the plain, less dense water slowly enough that it will stay above the saltwater instead of mixing with it. Watch what happens to the egg. Does it float to the top? It should stay right between the two layers of salty and not salty water. Can you explain why? It’s because the egg is less dense than the saltwater, but more dense than the plain water, so it floats between the two!