Do five fun egg-speriments this Easter while making meaningful science discoveries. Learn about heat transfer and insulation as you use eggs to keep ice cream from melting in a hot oven. Do a simple pH experiment that produces green eggs. Learn about density as you float an egg between a layer of salty and fresh water. Study air pressure with the classic egg-in-a-bottle project, and grow crystals in the egg “geode” project.
Is it possible to put ice cream in a hot oven without it melting? Oh, yes! Make this delicious dessert to try it out. There are many variations of this dessert—choose the type of cake, ice cream, fillings, and toppings that you like best. You can make one large dessert, or individual ones as we did.
What You Need:
- Cake or brownie mix
- Ice cream (flavor of your choice)
- 4 egg whites*
- 1/4 tsp cream of tartar
- 1/2 cup sugar
*Safety note: Sometimes the egg whites in the meringue won't be fully cooked. If you're concerned about salmonella, use pasteurized dehydrated egg whites or meringue powder you can buy at the store. You can also use liquid pasteurized egg whites from a carton, although the meringue won't fluff up as much as with fresh eggs.
What You Do:
- Choose a bowl (or individual ramekins) for an ice cream mold and line it with aluminum foil. Pack the ice cream in tightly and then freeze for several hours or overnight.
- Bake the cake or brownie mix as directed on the package. Allow the cake to cool all the way. Cut the cake to form a base for your ice cream mold. (Use a biscuit or cookie cutter for individual servings.) The base should be slightly bigger than the molded ice cream.
- When the cake is cooled and the ice cream well frozen, make the meringue: Use a mixer to beat the egg whites on high until frothy, then add the cream of tarter and beat until soft peaks form. Continue beating and add the sugar one tablespoon at a time until you have stiff glossy peaks. (Lift the beater out of the bowl – if the peaks stay standing up, your meringue is ready.)
- Preheat the oven to 450 degrees F.
- Place the cake on a cookie sheet, then remove the ice cream from the mold and place it on top the cake base.
- Use a spatula to quickly spread the meringue over the cake and ice cream, covering it completely. Make sure the meringue goes all the way down to meet the cookie sheet. (If you think your ice cream is getting soft quickly, you can put the dessert back in the freezer for 15-20 minutes before putting it in the oven.)
- Place on the middle rack in the hot oven and watch closely. Remove when meringue is golden brown, about 3-5 minutes.
- Serve immediately—and enjoy!
We know eggs change their form when heated. In this recipe, we see that egg whites also change their form when beaten vigorously! The two changes are caused by the same thing: globular proteins unfolding and forming new bonds with each other. When you beat the eggs, you're adding air bubbles to the mixture of proteins and water in the egg whites. Some of the amino acids in the proteins are attracted to water and some are repelled by it. The proteins begin to unfold so that the water-loving amino acids can move towards the water, and the others can move toward the air pockets. The unfurled proteins bond with each other, creating a network of protein that traps the air bubbles inside, making a nice fluffy, frothy meringue.
Now, the ultimate question—why didn't the ice cream melt completely when you put it into that very hot oven? The answer is that the meringue acted as an insulator, slowing down the transfer of heat. It works kind of like styrofoam (but tastier); the air trapped in small pockets in these materials makes them both good insulators.
Green Eggs and Ham
When you were little, you probably read the Dr. Seuss book Green Eggs & Ham. Do this easy pH trick to make green eggs just like in the book.
What You Need:
- Frying pan and stove
- Red cabbage (it's called red, but it looks purple!)
What You Do:
- Chop a 1/2 cup of cabbage, cover it with boiling water, and let it sit for 10 minutes until the water is dark purple. Strain out the cabbage.
- Crack an egg and separate the egg white from the yolk by carefully pouring the egg from one half of the shell to the other over a bowl. (Or you can pour the egg into a slotted spoon over a bowl instead.) Set the yolk aside.
- Mix a little cabbage juice in with the egg white. What happens?
- Grease the pan and let it heat up a little, then pour the egg white in.
- Set the yolk in the middle of the egg white and finish cooking!
Red cabbage contains pigments called anthocyanins, which change colors when they come in contact with acids (low pH) or bases (high pH), making them a natural pH indicator. When the cabbage juice comes in contact with an acid (like vinegar) it will turn red, but when it is mixed with a base it will turn bluish-green. What does this project tell us about egg whites, then? Egg whites are basic (also called alkaline) and so they turn the red cabbage juice green.
Make a regular egg float in a 250 ml beaker! Use a funnel to pour a layer of salt water underneath a layer of water. Do this by placing place the tip of the funnel at the base of the baker filled halfway with fresh water. Make sure its pointy side is up against the side of the beaker. Carefully add an egg and watch it float. Raw eggs float in salt water, but sink in fresh water.
Egg in a Bottle
Learn about the relation of temperature and pressure as you watch an egg get sucked into a bottle. This project requires adult supervision.
What You Need:
- Saucepan and stove
- Wide-mouth glass drink bottle (such as a Starbucks Frappuccino bottle – the mouth needs to be a little smaller than the egg. We used a large egg wih the Starbucks bottle, but with other bottles you might need smaller eggs. )
- Vegetable oil
- Strips of paper folded a couple times length-wise (slightly shorter than the bottle)
What You Do:
- Place the eggs in a saucepan and add enough water so that the eggs are covered by about an inch. Let the water boil for 5 minutes, then remove the pan from the heat and cover it. Let it sit for 25 minutes, then remove the eggs and dip them in cold water.
- Use a paper towel to coat the inside edge of the bottle mouth with a little bit of vegetable oil for lubrication.
- Peel one of the eggs, then dip it in water and set it with the small end down in the mouth of the glass bottle. It should be slightly larger than the mouth of the bottle, so it doesn't fit inside.
- Use a match to light the end of a strip of paper on fire. Lift the egg off the bottle, drop the paper inside with the flame down, and quickly replace the egg. Watch the egg wiggle a little in the bottle mouth, and then get sucked inside!
First, the science behind a hard-boiled egg: Egg whites are made of water and proteins. Proteins are made of long chains of amino acids, but in an egg the chains are clumped tightly together in individual spheres. (These are called “globular proteins.”) When the egg is heated, the proteins and water molecules begin to move faster. As they move and collide with each other, the individual protein chains start to “unravel,” eventually bonding loosely with other protein chains, forming a network of protein with water trapped inside. The consistency has changed from runny egg white to a soft solid!
So how does this squishy-but-solid egg get mysteriously pushed inside the bottle? The answer is all about air pressure. When you first set the egg on the bottle, the air pressure inside the bottle matched the air pressure outside, so nothing happened. When you dropped the burning paper into the bottle, it caused the air inside to heat up and expand rapidly. That expanding air pushed the egg aside and escaped from the bottle; that's why you saw the egg vibrating. When the fire consumed all the oxygen inside the bottle, the flame went out and the remaining air in the bottle cooled down. Cool air takes up less space, exerting less pressure inside the bottle. (The egg acted as a seal to prevent outside air from getting in to fill the extra space.) The result was an unbalanced force—the force of the air pushing on the egg from outside the bottle was greater than the force of the air pushing up on it from inside the bottle. Voila – the egg was pushed into the bottle!
How do you get the egg out again? You need to increase the pressure inside the bottle. Turn the bottle upside down and tilt it until the small end of the egg is sitting in the mouth. Now put your mouth close to the bottle and blow, forcing more air into the bottle and raising the pressure inside. When you take your mouth away, the egg should pop out – just be careful it doesn't hit you in the face!
Egg Crystal Geodes
Make sparkly crystal “geodes” inside real eggshells. First you'll need to make a supersaturated solution. For our geodes, we used magnesium sulfate and aluminum potassium sulfate. Can you think of other solids you can use to grow crystals? For this project, plan ahead and reserve the eggshells the next time you use eggs in a recipe.
What You Need:
- Raw eggs
- food coloring
- 250 ml beakers
- Funnel (optional)
- Plastic cups
- Epsom salt (magnesium sulfate), alum (aluminum potassium sulfate) or other solids commonly used to grow crystals, like Borax (sodium tetraborate), copper sulfate, etc.)
- White school glue and paint brush (for alum crystal geodes only)
What You Do:
- Crack the eggs close to the top of the narrow end. Remove yolk and white.
- Carefully place eggshell under warm running water and peel the membrane from the shell. Be very gentle! This part is tricky and requires much delicacy to avoid breaking the fragile eggshells.
- Once the membrane is removed and the eggshells are rinsed, invert them on a paper towel to dry.
- For alum crystal geodes, paint the inside of the shell with white glue. Then sprinkle with alum powder, and let dry.
- To make supersaturated solution, use your microwave to heat 100 ml of water in a 200 ml beaker just until boiling. Remove the beaker using hot pads or heat-resistant leather gloves.
- Stir in your solid (Epsom salt, alum, etc.), one spoonful at a time. Your solution should be clear. Heat it up more if all the solid won't dissolve.
- Add food coloring, and let cool for about 10 minutes.
- Carefully submerge the eggshell. Or set it in a clean empty cup and use the funnel to fill it with the supersaturated solution.
- Leave the eggshell and supersaturated solution undisturbed for several days or longer.
- After a few days, you should start to see crystals forming inside your eggshell. Use a spoon to remove it from the solution, or carefully pour the supersaturated solution out of the eggshell.
A crystal is a hard, solid substance made of molecules that bond together in specific patterns to form a shape with straight edges and flat surfaces. If you made more than one type of egg crystal geode, you saw that not all crystals have the same shape or size. The site where a crystal begins to grow, called its nucleation site, determines its size: fewer nucleation sites mean larger crystals, and many nucleation sites produce smaller crystals. A few molecules of magnesium sulfate or aluminum potassium sulfate (or whatever solid you used) found each other in the solution and joined together in a crystal formation. More molecules joined until enough gathered to form a visible crystalline solid. Chemists refer to this as a crystal 'falling out of'? the solution. If you left these crystals in the solution, they'd continue to grow.