# Summer Fun with Physics

#### Parents, are you looking for some fun yet educational stuff to do with your kids this summer?

Here’s an idea: make a bubble pool! This kiddie pool filled with dish soap and water kept me entertained for hours when I was younger, and little did I know how much I was learning about science in the meantime. Truth be told, I had a lot of fun and learned a lot even now, recreating my childhood summertime for this post!

It may seem like idle fun, but creating the ideal bubble solution, finding bubble wands and frames among household objects, and watching bubbles drift and shine with color all provide small basic lessons in physics. First, I’ll tell you how to set up the activity, and then I’ll talk about the science you can pepper into your conversations with your kids as you’re enjoying the bubbles. Some of these are high-level topics appropriate for high school students, too, so don’t count your older kids out of this fun activity!

### What you need:

• a kiddie pool — my recommendation is no bigger than 3 feet in diameter, otherwise you’ll need a lot of soap and water to fill it
• dish soap — any soap will do, but don’t try to substitute laundry or dishwasher detergent (these are designed so that they don’t create bubbles)
• a hula hoop — for big bubbles you can stand inside of
• straws — an absolute necessity: use these to blow bubbles directly into the pool, or thread string through straws to make differently shaped bubble frames
• other household objects that can be used as frames — hangers, paper towel or toilet paper tubes, tea strainers, grilling racks, etc.

### What to do:

Fill the pool about four inches deep with water, and add about one part dish soap per three parts water. You can also find other “award-winning” bubble solution recipes here. Letting your bubble solution sit overnight helps make better bubbles, as will using a cold bubble solution (it’s because of SCIENCE—see below).

Now, PLAY! Bubble frames and wands can be used to make all sorts of fun bubbles, and you can even have a bubble blowing contest using your straws in a small dish of solution. You’ll get an amazing bubble tower out of it.

Shake the hula hoop in the bubble solution for a bit, and then slowly lift it out of the pool—you’ll get a bubble column!

Have your kids take their shoes off, get completely wet, and stand inside the hula hoop before you lift the hula hoop. They can feel what it’s like inside a bubble!

A wet straw can be used to blow bubble inside of bubbles, or on top of other bubble planes, too. We did it on the bubble on a hanger frame.

Want to get a bubble that floats and drifts for a long time? When you are moving your bubble wand through the air, lift it upwards and make a circular swooping motion so that the bubble spins towards you when it is released.

### Now for some science:

Depending on the age of your children, you might use a more detailed or more simple explanation for any of these scientific principles.

The “skin” of a bubble is kind of like a soap sandwich, with a thin layer of water inside. If you poke a bubble slowly with a wet straw, it will pass through this soap sandwich without popping the bubble. You can even get a bubble to rest on a soapy hand without popping. When the water inside the sandwich evaporates, the bubble pops. So, the thicker the soap layers, the stronger and bigger the bubbles can be. Using corn syrup or glycerin to thicken the soap in a bubble mix can help boost your bubbles. Letting the bubble solution sit overnight allows the soap to really mix in with the water, and cold solution is thicker (in scientific terms, more viscous), so it makes for stronger bubbles.

#### What’s viscosity? It describes a fluid’s resistance to flow. Maple syrup is more viscous than water.

What else is more viscous than water? (Honey, soap, crude oil, and a smoothi, are all good answers.)

#### Another scientific principle relevant to bubbles is surface tension. This is kind of like the strength of the bubble’s skin.

The bubble solution has more surface tension than water, so it holds together. Surface tension results from how strongly the molecules of a fluid are attracted to one another. For more, check out this site and this video from Bill Nye.

This post could go on and on, but I’ll leave you with one final fun scientific tidbit. Look closely at any of the bubbles you’ve made, and you’ll see magical swirls of color on the surface.

The bubble solution didn’t look like this, so where do these come from?

#### These rainbow-like colors come from a property called iridescence.

Basically, light is being reflected by the top layer of soap on the outside of the bubble and the bottom layer of soap on the inside of the bubble. These two reflections interfere with one another, and create the spectrum seen on the surface of the bubble. See here for more details.

#### Sheila A.

Sheila Akbar is President & COO of Signet Education. She holds a bachelor's degree and master's degree from Harvard University and two doctoral degrees from Indiana University. She joined the team in the summer of 2010, bringing with her a wealth of experience teaching SAT, ACT, GRE, literature, and composition in both one-on-one and classroom settings.