Yes you can turn a cup of water upside down without spilling it! This nifty “magic” trick is sure to wow family and friends, and can be done with no fancy materials or supplies.

To start, fill a small plastic cup about half way with water. Place an index card on top.

Flip the cup over with your hand firmly holding the index card in place (it’s okay if a little water spills out), and make sure the index card is saturated.

Slowly remove your hand and… the index card sticks, without the water pouring out. There’s definite wow factor here, but it’s all thanks to the simple fact that water molecules like to stick together. Air can’t get in the cup as a result, equalizing the pressure, so the heavy water doesn’t pour down.

Travis also got a kick out of the way the index card pops off if you squeeze the cup even slightly, breaking the bonds of those sticky water molecules.

Want more cool water tricks this summer? Check out our old fun poking holes in plastic bottles, or playing with sticky string!

The next time you plan to make paper airplanes with the kids, throw in this little STEM exercise, first!

The idea is to hold a piece of paper (loosely from the top two corners) at about level with your chin, curling the paper slightly toward you at the top. Then blow down as hard as you can. Before we actually did the exercise, I challenged Travis to write down his hypothesis (fancy word!): Would his breath blow the paper down toward his chest, or up toward his nose?

His guess, surprising me because it is counter to logic, was… Up!

Well, it turns out he was right ,and the answer is thanks to some neat science. When the molecules above the paper move faster from your breath, the air pressure is becomes lower. That means the higher pressure air under the paper pushes it upward. So the paper billows up instead of down!

The same principal can be applied to the wing of an airplane, hence all this science before we got around to making our paper planes. Of course the next thing we did was to fold up lots of paper planes to soar all around the house!

Today, I gave Veronika full permission to raid the craft bin…in order to see what would sink or float from it, that is!

This was a cute variation on the simplest kind of “what sinks and what floats” activities for toddlers. Alternatively you could have your child gather toys from around the house, but using items from the craft bin gave us a wide variety of materials.

First, I simply asked her to predict what would happen as she dropped each item in. She was holding a metal clip to start and guessed, “Float!” Of course, it sank right to the bottom. Pom poms floated though!

We continued in this way, sometimes with unexpected results. Pony beads sank if they fell on their side. But if water evenly filled the hole in the center, they floated like inner tubes…until her little fingers poked them down. Pipe cleaners floated at first, but sank once fully saturated.

I thought tissue paper would be fun, and indeed Veronika loved that she could wad it up into little balls and then fish it out, but the dye started leaking off onto our hands. Whoops!

Wooden items (such as craft sticks) floated, while a big rubber eraser sank. And some things, like saturated strands of yarn, were purely fun to play with while wet! I loved watching her take note of each item as she plopped it in, and seeing her little brain register why some things stayed on the surface, while others fell to the bottom.

In sum, this is a neat way to sneak in a STEM lesson while a toddler thinks they’re just playing with items in water!