Big Bubbles! Pop! Baby Bubbles!

Big Bubbles! Pop! Baby Bubbles!

The inspiration for this experiment comes from some brand new research in what happens when bubbles pop. Now this may not sound like its cutting edge or brand new, but just this year researches from Harvard published some exciting findings about a two stage process that forms new bubbles from larger ones. I have put together some easy experiments that you can do at home or in the classroom that demonstrate their findings. What’s even better is we get to eat our findings afterwards!

First we always gather all of our equipment and ingredients.

Here is a list of what you need:

Straws

Large mixing bowl

Small mixing bowl

Measuring spoons

Measuring cups

Wisk or an electric beater

Cookie sheets

Parchment paper

Oven

Ingredients:

2 teaspoons dish soap

1 cup water

1 cup egg whites (the liquid ones will be easiest plus they are pasteurized)

½ cup regular sugar

Optional: chocolate chips, 1 teaspoon extract like vanilla, mint or orange, 2 tbsp. cocoa powder

Let’s start by making bubbles with soapy water. Gently mix the 1 tsp. dish soap with the 1 cup water in your small mixing bowl, use the measuring spoon to mix the solution so all of the soap gets used and dissolved. Now, using your straw, blow bubbles! How big a bubble can you make and how did you do it? Can you make lots of little bubbles? Once you have a heaping bowl full of bubbles, stop blowing and watch the bubbles pop. As the bubbles pop, notice that smaller bubbles are formed. This is exactly what the scientists at Harvard were looking at. Using very small bubbles under a microscope and high speed photography, they found that when a bubble pops, the walls collapse inward. First a donut shaped bubble forms from the trapped air then smaller bubbles form from the donut. What’s really amazing is this happens at the speed of sound making the popping sound we hear as the walls of the first bubble break the sound barrier! If you want to, you can try this same experiment using less soap and more soap. How well do different amounts of soap make bubbles? Record your results.

Now for the real fun. Using what we have learned about making small bubbles we are going to make meringue cookies. Meringue cooks are very light and crispy because they are made up of very very little bubbles of air surrounded by egg whites. We use egg whites and sugar so that we can bake them, they don’t collapse and they taste yummy.

Begin by preheating an oven to 350 degrees. Remember always ask an adult for help when using an oven.

Pour the egg whites into that large mixing bowl and begin to slowly whisk. Notice that at first, large bubbles are formed as you incorporate air. As you whisk faster and faster (use a folding motion if you’re doing this by hand) smaller bubbles are formed. Large bubbles are being formed, but they collapse into smaller bubbles to quickly to be noticed. Keep whisking until the egg whites are snow white and small dull peaks (often called soft peaks) are formed when you pull the whisk out. By this time the bubbles will be so small that you can’t even see them, but you know they are there because the clear yellowish egg whites are now solid white. When you get to this soft peak stage, slowly sprinkle in the sugar and any optional flavorings you are adding except the chocolate chips, mix these in at the very end. Notice that bubbles begin popping some when you add the sugar.

Soft peaks

Stiff Peaks

Continue whisking until the mixture is very stiff, glossy and shiny, and when you pull the whisk out stiff pointy peaks stick out. If you are adding chocolate chips, this is the time to do it.

Line the cookie sheets with the parchment paper and put spoonfuls of the egg white mixture onto the cookie sheets. Try to make even spoonfuls and space them about an inch apart on all sides.

Place the cookie sheets in the oven carefully to avoid burns, close the door and turn off the oven. It will take several hours to overnight to for the cookies to become completely crispy. Do not turn the oven back on; this will cause them to burn. Just keep the door shut for at least 4 to 6 hrs.  The cookies should be nearly or entirely white with little or no brown spots.

When the cookies are completely crisp remove them from the paper and store in an air tight container, the suck up moisture very easily and will become soggy. Enjoy!

More to Explore:

Pastry chefs have known for centuries that warm egg whites whipped in a copper bowl whip up faster and produce more volume. As a rule of thumb one egg white (about 1 oz) produces one pint, or 16 oz of meringue. But, with a little chemistry we can increase this two-fold. The copper bowl gives off copper ions that help the proteins bind to one another. Most of us do not have copper bowls in our kitchen, but we can find copper at the pharmacy in pill form. These pills contain copper gluconate, a ready source of copper ions. Using just a very small pinch of this will help whip up your eggs; too much though will make them taste funny. Another hindrance is the amount of water present in egg whites. While whipping you can use a water mister bottle and carefully increase the amount of water slightly and thus increase the volume of foam. This unfortunately makes a foam that collapses easier, so is not suitable for meringue cookies. Measure how much foam you can produce without any additives, than try it with just copper added, just water added and both added together to see how much meringue you can get from one egg white.