What You Need:
- Three whole eggs
- Three bowls
- Small saucepan with boiling water
- Kitchen timer
What You Do:
- Tell your child that you will explore some basic principles about eggs and how they can change. Start by checking her understanding: what will happen if you leave an egg in a bowl and don't touch it? What's inside? What happens if you put the egg in boiling water? (Warning: be prepared to explain that the eggs you buy at the store are not the kind with real chicks inside, so if you boil them you aren't hurting any creatures!)
- Invite your child to help you crack one egg into one bowl, and observe what happens. Name the parts—yolk and white—for your child if she doesn't already know them well. Leave them on the counter during your next phase, but check back now and then: has anything changed?
- Now heat up your boiling water, and gently place the other two eggs into it. Have your child watch you, and observe the eggs while staying a safe distance from the heat. Your child can also help you set the timer for three minutes.
- After three minutes, leave one egg to boil longer (set the clock for another twelve minutes), and pull out the other egg. Ask your child, "What do you think this egg will look like if I open it? Will it look like the one in the bowl?" (You can tell your child that that egg is a “control” in this experiment.)
- Since the egg is hot, you'll need to help with the next step. Take a knife, and split the egg into a second bowl. It will be a “soft boiled” egg—the egg white will have turned an opaque clear white, and the yolk, while still soft, will be more firm! And all this happened with just the addition of heat.
- By now, you should be ready to pull out the final egg. Again, ask your scientist to make a hypothesis about what she expects might have happened. Then split the final egg. Presto! It's a hard-boiled egg! Working together, observe what has changed now.
- What happened? Heat changed the “state” of the egg, and it will never change back. Why? Eggs are full of protein, and when you heated them, the proteins “unwound” in a process called “denaturing,” and recombined tightly. They're still the same substances that started in the egg—nothing came out and nothing was added—but the heat changed how they were put together.
What next? Eating, of course! You do want to make sure you cook the raw egg –it should not be consumed without being scrambled, fried, or added to some cooked concoction, lest you land your child with some bacterial bug. But the other two dishes are classic “comfort food.” Try cooking up some toast and serving your soft boiled egg on top, or perhaps mixing some mayonnaise into your hard boiled egg yolk to make a deviled egg. Science is all around us—even inside our tummies.