The Incredible Egg – Fresh or Old?

Science
Time 15 minutes
Age 5 & up
Group Size 4 or more
Tags Eggs, Experiment

Discover how old an egg is without having to crack it open!

Spring is a time of rebirth and renewal—and eggs! Many animals lay and incubate eggs in the spring, and in some cultures spring is a time in which kids paint, hide and eat lots of eggs. This makes it a great time to not only take a close look at eggs, but also to experiment with some of the things we can do with them. This activity is part of the Incredible Egg series of activities, which are designed to be done during the Spring—start your students off with this and other “egg science” activities, then move on to egg art, and finally take the Egg Drop Challenge!

Preparation

See the instructions for The Incredible Egg for preparations regarding all of the activities in this series.

For this activity, you will need to gather eggs ahead of time or ask parents to bring in any old eggs they have (and make sure you get the expiration date from the carton so you know which eggs are which).  For this reason, you may want to prepare for this activity several weeks in advance, to give some of the eggs time to age.

Make sure to try out all of the other Incredible Egg activities:

 

Egg Science Activities:

Egg Art Activities:

Culminating Activity:

The Incredible Egg – Fresh or Old?
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Suggested Materials

  • 4-6 eggs of different ages (Try to save up eggs that are 1 week old, 2-3 weeks old, 1-2 months old. Make sure you also have a very fresh egg)
  • 1 large, clear tub, filled 6-12 inches with water
1

Make it Matter

Opening Discussion

Ask your students how many of them eat eggs. Sometimes eggs sit in our refrigerator for a long time. Do eggs spoil? If so, how can we tell if they are old or fresh, without opening them up? Some students may say “look at the date on the egg carton”. This is, of course, excellent advice. But what if you took your eggs out of the carton?

The Challenge

Discover how to tell how old an egg is without having to crack it open!

2

Make it Happen

Doing the Activity

  1. Tell your students that your eggs got all mixed up and some of them are fresh, but some of them are old and might not be any good anymore. How can you tell the difference? Tell them that you don’t want to crack them open—you want to find out without having to do that.
  2. Ask your kids to share their ideas of how you might be able to tell which eggs are old and which are fresh, and encourage them to try some of these ideas out.
3

Make it Click

Let’s Talk About It

After they have brainstormed and experimented for a few minutes, bring your students together to talk about what they tried. Did any techniques work? Why do they think these techniques will give accurate results?

4

Make it Better

Build On What They Talked About

If they have not discovered this method, show your students this way of determining the age of an egg:

  1. Ask your students what they think might happen to the inside of an egg as it gets older. Do they think it might dry out? If they do, does that mean that air is somehow getting inside the egg? What might happen if air gets inside the egg?
  2. Fill the bin with water and place all of the eggs in the bin. Do they all sink to the bottom? Do they all float? You should notice that the different-aged eggs do different things—the fresh egg will rest on the bottom much as it would on a table. A slightly older egg might point one end up a little. An even older egg might point straight up, and the oldest eggs should float.

Suggestions

Since eggs are porous (some air can get into them), “air cells” grow in them as they age. The older an egg is, the larger its “air cell”. You can open the eggs up after this activity and inspect the shells to prove this point.

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