20 Minute STEM Activities | STEM Experiments in 20 Minutes or Less

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You and I know that STEM subjects are exciting. We can see the real world changes and the developments on the horizon, but what can you do for a kid who still needs it to be made a little bit more concrete? 

Here are some 20 minute STEM activities that will grab your students’ attention. Start making those big concepts explode in their minds!

Related post: 32 Cool Science Experiments for Kids

Baking Soda Volcano

baking soda volcano

The first science experiment that most of us ever did was a classic – the baking soda volcano! You can make this as complicated or as simple as you want. It’s not necessary but you can add food coloring for bright red lava, build a papier-mache volcano a week or two in advance and talk about evaporation in advance whilst it dries, or just cut the top off a soda bottle. 

First, put the volcano into a large waterproof tray. A roasting pan or a baking dish would do. To make the ‘lava’ put a cup of warm water into the dry volcano and add about six drops of red food coloring then about a teaspoon of dish soap. Get your bottle of white vinegar and get your little scientists ready. 

Pour the vinegar slowly into the volcano and boom! You have an erupting volcano. You can now explain that while real lava is molten rock, the lava in your experiment erupts because of the combination of the acid (vinegar) and the base (baking soda). They react together and cause the production of salt and carbon dioxide gas that forces the ‘lava’ out of the volcano in an eruption. 

Simple Ciphers

simples ciphers make a great STEM activity

Math can be elegant and simple, and there is always a thrill to cracking the answer. But a lot of kids do that most days of the week. So you can dial up the interest factor by making a simple cipher.

Give the kids a coded message (if you really want to get them excited) and make it the location of a piece of treasure. You can then give them the code to crack it. Let them work through the message and then race to the location of the hidden treasure. You can build on this later by having older kids write their own cipher and trade messages!

Human Slingshot

human slingshot

This one is sometimes best to do outside – it’s a big crowd pleaser! A simple human slingshot is easy to make. You could buy a small slingshot to demonstrate but it’s a lot more fun to buy a water balloon cannon. They are usually cheap and freely available from the big online retailers or toy stores. 

They are long loops of elastic cord with small patches of fabric sewed into them as a basket. If there are three of you or more, you can get two kids to hold the two ends and then have a third person load and pull back the basic catapult.

Some options for what to put into the basket include soft coloured balls, balloons filled with a coloured chalk soluto make a splash when they explode. You can shorten and lengthen the elastic to show how it exerts different levels of force on the flying objects, or you could show different splash patterns with the basic chalk paint mixture. It’s a great option for showing how applying force can cause a physical reaction. 

Offline Coding Grid

offline coding grid

You might think you would need a computer to teach coding. You might also think it would be an activity that kids would do alone. But you couldn’t be more wrong. Coding can be done as a team – whether it’s indoors or outdoors!

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Coding for a computer programme is normally done in binary code or a programming language like java but the fundamentals are very simple. By using symbols or characters in different combinations, you can issue an instruction to a computer or in this case a ‘robot’. 

All you need is a large square of floor space, some coloured paper or pens and either chalk or white masking tape. First draw out a grid on the floor with the tape or chalk, make it at least 5×5 squares. Next, make your code. If you have colored paper then make your colors and direction arrows match. For example, forward arrows on red paper, left arrows on blue, right arrows on green, and so on. 

After that, designate a person to be the robot and mark a square with an X as your finishing point. If you have more room, you can do two grids and have two teams to race. Have the ‘robot’ start at the opposite side of the grid and then have the other kids lay down the right piece of paper with the right symbol to move them towards the finish line in the minimum number of moves. And voila! You have your own simple coding language and optimisation exercise.

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Frequently Asked Questions

20 minute stem activities

Can I do these activities indoors?

Yes! You can do any of these activities indoors. Just take a few sensible precautions like using tape for the coding grid instead of chalk, put a waterproof tray underneath the volcano and if you are making your human slingshot indoors, choose a large room without breakable objects where all the people in the room can stand back. 

 How can I make these experiments suitable for different ages?

There are lots of ways you can tweak the experiments to make them a little bit more challenging for older kids. Consider using a slightly more complicated cipher to make your code breaker exercise harder, add obstacles in the way of your ‘robot’  or a larger grid to make coding more difficult. A volcano never loses its appeal but for older kids, you could add a diet coke and mentos volcano to compare a physical reaction vs chemical reaction.

Will I need expensive supplies?

Absolutely not! These supplies we’ve listed aren’t costly. Most of them would cost no more than $5 if you even have to buy them new. The vast majority can be recycled, or can found lying around somewhere. If you are a little bit creative, you could recycle other supplies like crunched up newspaper instead of balloons for the slingshot. 

Mark Coster, BSc(Hons) PhD MRACI CChem
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