Science Smarts: The best time of year is the hardest time to focus

By Patty Rooks on May 24, 2025.

I know this time of the year can be hard to stay seated in the classroom for students. We are all looking out the window at the beautiful weather imagining we were outside. So, I thought I would share one of my favourite experiments guaranteed to keep their attention! Let’s get started.

*Remember to ask an adult before doing this experiment.

Materials

– Small glass mason jar with a screw on lid

– Scissors

– Index card

– Water

– Small piece of mesh screen

– Towels and a mop (just in case)

– Science volunteer

Procedure

1. Before you start, you will have to cut the mesh screen to fit the lid of your mason jar. If you want this to be a “trick” try and hide the screen as best you can by trimming it up to fit securely in the lid.

2. Fill mason jar with water.

3. Have the science volunteer come up and tell them that they may or may not get wet!

4. Hold the index card over the lid of the jar. Invert it and hold it straight up and down (this is important, and you will see why later) over the volunteer (you may want to practice this in advance!).

5. Observe.

6. If you did it correctly, the card should have stuck to the lid and no water escaped onto your volunteer!

What is going on?

I absolutely love this experiment because there are so many scientific principles at play. First of all, atmospheric pressure is at play. The pressure exerted by the surrounding air is the force that holds the index card in place, so your volunteer does not get wet.

The pressure of the air molecules is pushing on the card and exerting a force that is greater than the pressure of the water pushing down. One of my favorite principles to demonstrate is surface tension. Water is a special substance and the surface of it acts like it has a thin layer of skin holding it in place. There is also cohesion. The water is able to stay put in the jar even though you remove the index card because the molecules of water are held together through cohesion. Be careful, if you tip the jar at all, the water will come rushing out and drench your volunteer. This is due to air rushing into the jar and pushing the water out.

Calling all educators! Booking for our Hands on Learning Kits for the 2025-2026 school year will open up June 1 – you can book for the entire year if you have your planning ready. Email your requests ASAP as it is first come first served. We are excited to have a partnership with the Medicine Hat Public Library where they are picked up and dropped off to suit your schedule. As well, keep reading here as there will an exciting announcement on a new offering for the Junior High Classroom thanks to the generous support of TC Energy!

Patty Rooks, senior scientific consultant PRAXIS. Praxis has moved! We are now located in the Community Futures Entre Corp Building at 556 Fourth Street SE, T1A 0K8. Call us at 403.528.0182, or email praxis@praxismh.ca. Keep reading our weekly column for more exciting details on what we are up to these days

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