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A Science Demo Day That Students Will Never Forget

The last couple of years I taught, I did an elaborate science demo day for Halloween.  This is one of those experiences that students will remember when they look back on their middle school experience.  I encourage you to dig deep and really put some thought into the presentation.  It will go a long way in making this something students will talk about forever.

Mad Science Lab Setup

I always did a science demo day on or around Halloween, but it could be done at anytime throughout the year.  The theme I've used in the past has been a mad scientist testing out his latest experiments in his laboratory.  It's a natural fit for most science teachers, right?

Let's first talk about the costumes.  I dress up as a mad scientist.  You probably already have a lab coat and some funny glasses.  You can find a wig at a local party store or at Amazon.  I throw on some safety goggles as well.  My partners in the past have also dressed up like nerdy scientists, and it's been a hit.

Last year we were able to fit all of our classes into a flex space (teaching theater).  It provided ample room for all the classes to view the demonstrations.  We set the mood of the room by putting up black butcher paper on the windows.  This served two purposes.  We wanted it to be dark for some of the demonstrations, but we also didn't want kids knowing what was happening in the room during setup and throughout the day.  It's inevitable that once your first set of classes have seen the demonstrations that students from all over campus are going to swing by and check out what's going on.

At the front of the class we pulled out a lot of glassware and setup our pretend lab.  This is a great time to get out your ring stands, test tube racks, flasks, beakers, etc.  The key to it looking like a creepy laboratory is to use some atomic glow from Steve Spangler Science.  This concentrate can be poured into water, and when a black light is used it's used it is really impressive.  We added some glow sticks into the test tubes.  They can be found at Target or a dollar store for very cheap.  Adding dry ice to the mix sets up the theming perfectly, and students are going to be instantly engaged.  I found dry ice at my local grocery store.  They sell it by the pound, especially this time of year.  Be sure to use gloves when handling it!  Below is a quick little video of our setup from last year.  I unfortunately didn't get a video of the dry ice.

Something is Different Today

In order to set this day apart from any other day you are going to have to sell it.  When students walked into the classroom and saw flasks brewing and heard scary music playing, they were immediately engaged with the atmosphere.

Once the bell rang we introduced ourselves to the class and told them the teachers were out for the day.  We said we were their 'fun' substitutes and never broke character the entire day.  It's funny because even throughout the rest of the year we would always talk about that one day where the subs came in and blew our lab up.  Obviously, the kids knew it was us, but they really bought into the story we were trying to tell.

You will also want to take 30 seconds and set the expectations for the day.  There's plenty of opportunity for this to get out of hand if you don't set clear expectations up front.  The biggest safety issue is that everyone remains in their seat unless they are called upon to be part of an experiment.  Anyone participating in the demos should also have the proper safety equipment on.

The Demonstrations

My class periods were about 40-45 minutes and we were able to get through all of the demonstrations every period.  Below are the demonstrations we used.  Some of them cost money to set up, but obviously you can substitute in any of your favorite demonstrations.  The science department was able to help us fund some of the costs, but we did spend some of our own money.

The transition from demo to demo should be fluid.  Think about a street magician.  You don't want any downtime between the demos, because students will quickly lose interest.  We were able to do this using three science teachers - we just rotated who featured each of the demonstrations.  One year, I was able to have two students help me out with the demos all day long.  Your mileage may vary depending on the buy-in from your administration.

Demo #1 - Wine Glass Pendulum


  • 3 foot piece of string
  • Washers if variable sizes (14:1 ratio)
  • Wedding ring (washer could also be used)
  • Wine glass or coffee cup

This is a great starter demo and will require someone from the audience to participate.  I like to do it twice.  The first time just do it with washers on both ends, and then have someone come up and do it with a glass or coffee cup for a better effect.  In the video Steve uses a spoon attached to one end.  You can see that it gets hung up as it slings around.  I would just stick with washers or a ring.

Demo Tips:

  • Make sure the ratio is 14:1 in weight.
  • As it swings around your finger you may have to put your thumb on the string before it unwinds again.
  • Ask the class before you drop it for the first time, "What's going to happen?"  They will almost all say the weight will pull the lighter weight over your finger and fall on the ground.
  • Call up an audience member for the wine glass or coffee cup demo.
  • Put a folded towel underneath the glass just in case :)  I've never had it break, but things can go wrong.

The Science:

It's important to talk about the science behind all of the demos, but I'm going to go out on a limb here and tell you not to dwell on it.  Talk about it briefly, and move on to the next demonstration.  For this demonstration you can talk about potential energy converting to rotational energy as the glass falls.  Energy is always transforming from one form to another.  It's really as simple as that.

Although this is a pretty cool little demo the kids are going to be wondering, "Is this all?"  This is a great opportunity to let them know the math teachers have asked for any unimpressed students to report to their classroom for worksheets.  Have some fun with the audience.

Demo #2 - Baby Diaper 3 Card Monty


  • 3 Solo or foam cups
  • a scoop of water gel
  • water

This demonstration will start to get the kids excited because it's almost certainly going to fool all of them.  Watch the video to learn how it's done, but definitely add some more energy than old Science Bob.

Demo Tips:

  • I like to do it three times. On the third time put the water into the cup with the powder.
  • The first time you switch the glasses around do it really slowly.  Speed up on the second time, and then go really fast on the last time.  You could even take it up a notch by telling the entire class that you'll give them all Jolly Ranchers if they can tell you which glass has the liquid water on the 3rd time.  Ham it up!  Showmanship is your friend.

The Science:

The powder is actually a finely cut polymer that is super absorbent.  Explain to them this is actually the same polymer that is found in baby diapers.  It absorbs all of the liquid into the diaper and turns into a gel.

Demo #3 - It's Time for the Holidays - Let's Make Some Snow


The background for this demonstration is that you've been working on a new formula snow so you can open a ski slope out behind the school and retire a millionaire.  Steve is a master of setting up demonstrations and using humor while doing so.  This demo is a quick one.

Demo Tips:

  • Ask the students what will happen before you pour the water in.
  • Practice the demo a couple of times so that the snow will overflow from the beaker once you add the water to it.
  • Take handfuls of snow and toss it on the first few rows of the audience.  It's harmless.
  • Everyone is going to want to touch it.  I'd keep it up front and allow kids to come up after class if you choose to do that.  I wouldn't pass it around unless you're much more trusting than I am.

The Science:

The powder is the same super absorbent polymer from the last demo.  The only difference is how it's cut into fine pieces.  It doesn't gel together like the other cut polymers.

Demo #4 - Beach Ball Blower


  • Hairdryer
  • Ping pong ball
  • Beach ball
  • Leaf blower

This is a fun one which has an unexpected outcome.  I called the hair dryer my 'molecule machine' just to make it a little more fun and engaging.  You can have a volunteer come up and do this one.  Ask them what is going to happen if you point the hair dryer straight up and then put a ping pong ball in the air stream.  Have them do it.  Once the ball is floating in the air stream ask them what will happen if you start to tilt the hair dryer at a 30 degree angle.  The amazing thing is that the ball remains floating in the air even when it's not directly above the hair dryer.  Check out the demo below from an old video I made.  Heads up, that website doesn't exist anymore.  All the goods are now found on this site.

That's cool and all, but it gets really awesome when you bust out the leaf blower from under the desk and do the same demo with a beach ball.

Demo Tips:

  • Don't show the audience the leaf blower and beach ball until you're ready to use them.  Maybe even ask them how you could expand on the experiment to give it a bigger wow factor.
  • If you tilt the airstream too fast the ball will fall off.

The Science:

The Bernoulli Principle states that as an air stream (or fluid) speeds up, a decrease in pressure will occur. Fast moving air will cause a drop in air pressure (relative to the air pressure outside the column of moving air).  The moving column of air produced by the hair dryer causes an area of low pressure. The pressure in the column of air is lower than the pressure outside of the column of air. The ball cannot move into the area of the higher pressure air. When it moves in that direction, the higher air pressure pushes it back into the low pressure column of air.

Demo #5 - The Unpoppable Water Balloon


  • Balloons
  • Sink
  • Matches

Balloons, water, and matches typically aren't something I would recommend for a middle school science classroom, but this one is great and as you'll soon find out why it's the most rewarding demo you will do all day long.  First, blow up a balloon and then ask the audience what is going to happen when you light a match and touch the flame to the bottom balloon.  Of course, it's going to pop.  Demonstrate that.  Fill up another water balloon with about a cup of water and then blow air into the balloon so it is fully inflated.  Once again ask the audience what is going to happen if you touch the flame to the bottom of the balloon.  They should say that it will also pop.  They will be wrong.

This is where it gets good.  Ask the audience if anyone would like to test it out by sitting in a chair underneath the water balloon while you put the match to it.  This is your opportunity to find a student that has been a little challenging in your class all year and invite them up.  They probably will already have their hand up because they like to be on stage :)  Make sure to have them remove any electronics from their pockets and have them agree not to get mad if they happen to get wet.  I always tell them no one has gotten wet all day long, but it's possible.

Have them sit down in the chair and then hold the water balloon over their head.  Light the match and then hold it directly underneath the area of the balloon with water.  It won't pop.  You can hold it there for quite a long time without popping.  Tell the kid they were lucky today and then immediately take the match and touch it to the part of the balloon that has air in it.  The balloon will pop and the kid will get soaked.  You'll be an instant hero!  Have a towel ready for the student and thank them for being a good sport.

Demo Tips:

  • Make sure the audience participant doesn't have electronics in their pockets.
  • The kids will secretly love you for drenching the class clown.

The Science:

Water is a great conductor of heat and the heat transfers from the match directly to the water without popping the balloon.

Demo #6 - Boo Bubbles


This is a great demonstration when talking about the properties of dry ice.  You could probably create your own setup here, but the one sold on the SS website is great and works every time.

Demo Tips:

  • You don't need to screw the lid all the way on.
  • The cotton glove is mandatory because the dirt and oil on your hand will break the bubbles.
  • Allow a student volunteer to come up and play with the gas bubbles.
  • Make sure to practice this one a couple of times before doing it in front of students.

The Science:

Dry ice is just frozen carbon dioxide.  It transitions from a solid to a gas without turning into a liquid. This process is called sublimation.

Demo #6 - Dry Ice Crystal Ball


  • Dry ice
  • Large Tupperware or glass bowl with a smooth rim
  • Long strip of old t-shirt or towel
  • Dish soap

For this demonstration you can continue to talk about the properties of dry ice or just go with some made up story about wanting to make a crystal ball to see into the future to find out who is going to pass or fail the class :)  We're all about having fun here.  This is a great time to kid around with the kids and build relationships with them.  You certainly don't want to pick on anyone or hurt feelings though.

Demo Tips:

  • Make sure the container is very clean and free of soap residue on the inside.  Once soap gets in the water it will create a bunch of small bubbles and ruin the effect.  This becomes an issue when you do this experiment 6-8 times a day.  Just make sure to wash it between demos.
  • Make sure the water is nice and hot.

The Science:

Dry ice is just frozen carbon dioxide.  It transitions from a solid to a gas without turning into a liquid.  This process is called sublimation.

Demo #7 - Atomic Worms


This demonstration is a lot of fun and produces a pretty disgusting outcome.  I like to set this one like I'm preparing my dinner.  When you squeeze one liquid into another liquid it becomes a solid. Lots of fun!

Demo Tips:

  • The activator solution will last you the entire day.  You won't need to make a new batch each time.
  • I have the sense of humor of a junior high student, so I like to hold a big long one right up to my nose and then ask the class if I have something hanging from my nose.  They love that.
  • I would refrain from passing them around unless you want a mess

The Science:

Worm Goo is a long chain of molecules called a polymer. When the Worm Goo comes in contact with the Activator, the goo immediately changes from a liquid to a solid! That’s because the Activator acts a cross-linking solution that links the long strands of polymers in the goo together.  I'm not 100% sure if the science is completely accurate on this next statement, but I like to say a precipitate was formed.  A precipitate is an insoluble solid that emerges from a liquid solution.

Demo #8 - Air Cannon


For our class I made a smaller version of the one that Steve uses in this video, but it was still very effective.  It's really fun if you have a couple of them and can allow students to compete by knocking cups off the heads of audience members.

Demo Tips:

  • Cutting the hole in the bottom of the can is the hardest part.  I ended up using a serrated knife to do the job.  It doesn't have to be perfect.
  • Adding a smoke machine makes this demo a lot cooler.  Everyone wants to see smoke rings fly across the room.

The Science:

The ball of fog/air that shoots out is really a vortex. The vortex is created because the air leaving the trash can at the middle of the hole is going faster than air leaving around the edge of the hole. This science experiment illustrates that air occupies space. As you hit the rubber sheeting it pushes into the trash can. As a result,  the volume inside the can decreases and pressure increases.  That pressure increase pushes some of the air out of the hole in the bottom. The smaller the hole you cut, the greater the velocity the air/fog will come out when you strike it.

Demo #9 - Whoosh Bottle


  • Rubbing alcohol
  • 5-gallon jug
  • Long neck lighter
  • Fire extinguisher

Disclaimer:  Don't be an idiot with this one.  You need to make sure anyone nearby has safety goggles on and that a fire extinguisher is readily available.  We have always done this indoors, but we were in a room with high ceilings.  Students should not participate in this demo because it can be dangerous.  It's a highlight though.  They will talk about this one.

Demo Tips:

  • Make sure to coat the inside of the jar really well with the alcohol.
  • Shake up the water bottle with your hand covering the opening to allow the vapor to build up.
  • If you can time it correctly this demo goes great with the song from Pitball called "Fireball".  We were able to time it to where the flame happens right when he belts out "FIREBALL!"  It was awesome.

The Science:

The Whoosh is created because the expanding hot gases are trying to quickly escape from a narrow opening at the top of the bottle.  

Take a Bow

I've done this with my classes for the last several years and it truly is a magical day.  You are providing the students with an experience they can't get anywhere else.  I survey my classes at the end of each year, and this day is inevitably one of the favorites year after year.  Encourage other teachers and admin to come in and see what science is all about.

What are some of your favorite demos?  I'd love to continue the conversation in the comments below.


Although most of the science experiments above are regarded as low hazard, the author and publisher expressly disclaim all liability for any occurrence, including, but not limited to, damage, injury or death which might arise as consequences of the use of any experiment(s) listed or described here. Therefore, you assume all the liability and use these science experiment projects at your own risk!

Some links within the article are affiliate links to Amazon in which I receive a small commission at no cost to you.  I have no affiliation with Steve Spangler other than I love the way he makes science accessible to every

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