Science Demos

An incomplete list of informative and/or cool science demos you can do for your kids and/or yourself.

This is not intended to be a complete list. Selection criteria are that each demonstration needs to show some interesting phenomenon and be practical to reproduce with relatively little in the way of expenses or technical skill. Some of these can be done in thirty seconds if you have the materials on hand; some take much longer.

For each project I've embedded a video which shows the project, but may omit details (e.g. quantities); you may need to Google.

I'm always interested in collecting more of these. Please email [my username] @ gmail, or open an issue or PR on Github.

In no particular order.

§ Cloud chamber particle visualizer

With some dry ice plus materials you likely have around the house, you can see tracks from cosmic rays.

Notes:

• Many other versions on Youtube, some of which don't require dry ice.
• As a bonus, you can add a piece of radioactive material to see many more tracks coming off of the material.
• Takes a few minutes for the alcohol vapor to condense enough; be patient.

§ Polarize light with sugar water, make colors

By shining light through a polarizing filter, then a solution of sugar water, then another polarizing filter, you can get colored light from white, with the color depending on the angle between the filters and the depth of the solution.

Notes:

• Heavily saturated sugar water works as well as corn syrup; use whichever is easier.
• 3blue1brown has a fancier demo and a detailed explanation.

§ Three polarizing filters

Polarizing filters don't just filter light; they actually act on it. You can let more light through by adding an additional filter in the right way. Takes five seconds to demo if you have the filters on hand.

§ Water is diamagnetic

You can push on water with a magnet. The effect is weak, so a good magnet and setup is essential.

Notes:

• Instead of using a test tube as in the above video, you can fill a bottle cap full of water and float it on a small square of styrofoam.
• You can also demonstrate it using the light-distorting effect of water.

§ Drop a magnet down a copper tube

Magnets fall slower when dropped through a conductive tube.

Notes:

• In this and all other demos, use a strong neodymium magnet.
• You can get copper pipe from a home improvement store. They'll usually cut it for you; a foot is a good length.
• You want the pipe to be about 2x the diameter of your magnet: as small as you can get it while still being able clearly see the magnet not touching the walls.
• It's possible to demonstrate the Lenz effect with just a magnet and an aluminum can, but it's not as impressive as the pipe.
• It's also possible to use a wire wrapped around a non-conductive tube, which can light up an LED with the induced current. This will require a lot of turns of wire, though. Because the LED is a diode, only one choice of orientation of the magnet when dropping will work to light it up (I think).

§ Rainbow chocolate with diffraction grating

Diffraction grating is a nanoscale physical pattern which splits light by wavelength. You can transfer the pattern to choclate to get very pretty oil-slick rainbow patterns.

Notes:

• The process is somewhat fiddly.
• Here's another example with written instructions.
• Diffraction grating is cheap and cool, but be careful handling it: the oil from your hands is enough to disrupt the effect.

§ Measuring the speed of light with a microwave

By using the wavelength of your microwave and measuring the distace between hot spots in your food, you can calculate the speed of light.

Notes:

• You'll have to trust the frequency printed on the microwave.
• Videos of the process make it seem like you'll get a precise result, but in practice there's a pretty wide range of plausible distances between dead spots you might measure. But you should still get the right order of magnitude.

§ Measuring the speed of light the original way

If you don't want to trust the number printed on your microwave, it's possible - with a lot more work - to actually physically observe lightspeed delay, using a rapidly spinning disk with holes and a laser shining across several miles.

Notes:

• This is a lot more work than most projects on this page. I've included it anyway because it is so cool.

§ Making plasma in the microwave

Microwaving a lit match (among other options) will make plasma.

Notes:

• Grapes and aluminum foil also work, and with slightly different effects.
• The plasma is very hot and can damage the integrity of the glass used to trap it, so you should probably use something disposable (e.g. an old mason jar) and throw it out after.

§ The double slit experiment

With a laser and a piece of hair, you can see interference patterns which have no classical explanation. A proper double slit works a little better but is not necessary.

Notes:

• Be careful with lasers. They're often more powerful than they claim and can do permanent damage to your eyes.
• Another good way of doing this is by using an adjustable crescent wrench with a couple of razor blades attached so you can dial in a precise slit and see how the interference pattern changes as the opening changes.

§ Turning pennies silver and gold with zinc

Notes:

• The chemistry of this reaction is pretty interesting.

§ Growing tin crystals with electricity

Notes:

• Working with bare wires and a serious power supply is dangerous; stick to a standard battery unless you know what you're doing.

§ Using an oscilloscope to watch electricity propagate when you flip a switch

If you run a kilometer of wire and have an oscilloscope, you can see some nontrivial behavior when closing a switch.

Notes:

• If you're going to run this experiment you should probably be the sort of person who already owns and knows how to use an oscilloscope.

§ Submerging a circuit in water makes electricity flow slower through it

This is just like the above experiment, but you put a pipe full of water water around part of the circuit and observe that it takes longer for the circuit to fully complete.

§ Light changes angle when passing through glass

Shining a laser pointer through a glass slab lets you easily visualize refraction.

§ Camera obscura

Cardboard and a lens lets you reproduce an image.

Notes:

• Tracing paper works well for the projection material. Wax paper might also work.
• You can turn a whole room (with a window) into a camera obscura; you don't even need a lens.
• A good follow-up is to make an actual camera.
• A simpler variation is to project the image of a candle with a lens. This requires only a candle, a lens, and a piece of paper. And because the light is basically a single color, you can use a simpler lens without worrying about chromatic abberation.

§ Resonance

You can see resonance with a couple of tuning forks and a pingpong ball.

Notes:

• The wooden boxes in the video above make the effect stronger but are not strictly necessary; you just have to get the forks very close.
• A variant of this is to physically hold the forks, so you can feel one start to move when the other is struck.
• You can adjust the resonant frequency of a fork by sticking a magnet to it (or making similar adjustments for non-ferrous forks).

§ Measuring expansion of metal due to heat

With a sufficiently precise measuring tool you can see metal expand just from warming it up with body heat.

Notes:

• You need a really precise dial indicator. Try Mitutoyo. You also need gauge blocks or similarly precisely machined objects.
• Try looking up the (linear) thermal expansion coefficient for your material and checking against what you see. Is the implied change in temperature plausible?
• If you have the dial indicator, you can also measure the thickness of a Sharpie mark.

§ Cloud in a bottle

Add some smoke and water to a bottle, pump air in, then suddenly let it out and you get clouds. The effect is more dramatic with rubbing alcohol instead of water (but skip the smoke).

Notes:

• You can get a similar effect without a pump by twisting a bottle to create the pressure.

§ Diet coke & Mentos

Drop Mentos candy in soda and get an eruption as the candy creates nucleation sites for the dissolved CO2. You've probably seen this but it's still cool.

Notes:

• This works just fine with soda water; you don't actually need diet Coke. I recommend against soda with sugar in it because it's a pain to clean and will attract ants.
• The effect scales (within reason) with the number of Mentos - make a tube from a piece of paper to hold a stack and drop them all in one go.
• Old soda loses some of its CO2, so this is best done with a new bottle.

§ Coloring coal

Soaking coal in a solution made from some cheap chemicals will give it very cool colors.

Notes:

• You can buy coal, potassium ferrocyanide, ferric chloride, and sodium bisulfite from Amazon.
• The original patent is here.

§ Unmixing corn syrup

Corn syrup is very viscous and has a very low Reynolds number, which means that it can be made to flow extremely consistently - so consistently that you can actually reverse the operation and most molecules will end up close to where they started.

Notes:

• This video has a little more detail about the setup.

§ Dissolving eggshells

Soaking an egg in vinegar for 24-48 hours will dissolve the shell while keeping the outer membrane intact.

Notes:

• You might as well try a few at once - they're fragile and may break. It's still raw egg inside.
• You can wash the remnants of the shell off with water.

§ Coat an egg in soot

Coating an egg in soot will make it hydrophobic, which means if you dunk it in water it will have a skin of air.

Notes:

• Here is a 60-second explanation.

§ Electric wind

A sharp point under high voltage ionizes air, which moves away from the point, which creates thrust. This can make an aircraft with no moving parts.

Notes:

• This video goes into detail about how to make one.
• This is a fan instead of a lifter based on the same principles. It links to these 5V to 400kV transformers, which frankly sounds a bit insane.
• Getting power from a USB battery pack is one of the easier electronics projects, and should be sufficient to drive the above transformer.

§ Seeing the curvature of the earth

With a wide enough lake, on a calm day, you can actually see the curvature of the earth.

Notes:

• There's not a lot of places in the world where this is possible, and you have to get lucky with the weather. But this video is almost a religious experience, so if you have the chance, I think it's worth it.

§ Supercooled water

You can get water below its freezing point without it turning solid, and then freeze it all at once.

Notes:

• Don't use mineral water; it needs to be pure.
• 2.5-3 hours seems to be the recommended length of time to keep the water in the freezer. It will freeze on its own eventually.
• Try a few bottles at once; the process is delicate.
• You can pour the water onto ice for a neat effect.

§ Measuring the speed of sound in a solid object

With a force sensor and an oscilloscope you can measure the speed of sound in an object fairly precisely.

Notes:

• The end of the above video also gives a great example of how factors we normally neglect can throw off your results.

§ Baking soda & vinegar

Mixing baking soda and vinegar makes CO2. Baby's first chemistry experiment.

Notes:

• Best done in a ventilated area. Don't suffocate yourself.

§ Rubens Tube

A carefully designed tube can demonstrate how sound is pressure, using fire.

Notes:

• While you can build your own, this is one of those things it might be simpler to purchase.
• If you end up owning a Rubens tube, you are morally obligated to hook it up to the music when throwing parties.

§ Finding your blind spot

Cover one eye and look at a specific image from the right distance and part of it will disappear, because your eyes are badly designed.

Notes:

• The video has an example you can run on yourself. Wikipedia also has a good one.
• This is one of the clearest examples of your brain lying to you. It sure doesn't feel like you have a blind spot. But you do.

§ Static electricity

There are many cool demos of static electricity, though they usually amount to "this thing now attracts/repels this other thing". I've arbitrarily chosen one to embed here but you should look around for others.

Notes:

• A Leyden jar is a good next level. You can build up enough charge to be painful, so be careful.

§ Superconductors

Superconductors have all sorts of neat properties. Levitation is particularly flashy. You'll need a superconductor and liquid nitrogen (unless room temperature superconductors have been invented since this writing), so this one is a little less accessible.

Notes:

• YBCO superconductors can be bought (among other places) here.
• Mobius strip tracks are particularly neat.

§ Electrolysis

Split water into hydrogen and oxygen with electricity.

Notes:

• Hydrogen plus oxygen is explosive, so be careful. I recommend a split output setup so you don't immediately mix them.

§ Crookes radiometers work on heat, not light

A Crookes radiometer is a neat toy which spins when in light. With a refrigerant, you can demonstrate that the effect is actually thermal.

Notes:

• You can also use an LED bulb and an incandescent bulb to demonstrate that the incandescent bulb is putting out a lot of energy outside of the visible spectrum.

§ Fluidized bed

Forcing air through sand makes it behave like a liquid.

Notes:

• The video above says you can run this off an air compressor, but the build docs say that only provides enough flow for a small (1ft x 1ft) tub.
• You need very fine material for this to work - apparently glass bead sandblasting abrasive works well. I couldn't find details about which grit, but in this video you can see an SKU which corresponds to this 60 grit material, which is relatively coarse as far as blasting abrasives go, so probably any glass bead abrasive will work.

§ Ball bearing shockwave

Hitting large ball bearings together generates enough heat to burn paper.

Notes:

• You want 2 inch diameter steel ball bearings. You can get them off Amazon.
• This video has more details about how this works. It also points out you get a neat pattern by interposing aluminum foil instead of printer paper.

§ Extracting DNA from a strawberry

Some household chemicals are enough to isolate DNA from plant matter.

Notes:

• The DNA looks like a glob of snot. I'm not sure if there's something more interesting you can do with it.
• Try it with other plants too!

§ Pendulum synchronization

Placing identical pendulums on a base which can move will lead to them being in sync ("coupled").

Notes:

• This can be done with any pendulum; metronomes are dramatic but you can make one yourself.
• You might end up with some things precisely out of phase instead of precisely in phase. You might enjoy trying to figure out the conditions which lead to outcome or the other. Try playing with more pendulums, or different bases.
• More about synchronization, and more examples, in this video.

§ Growing crystals

You can grow crystals at home in a few weeks using alum you can buy in the spice aisle and a fine thread or fishing line.

Notes:

• There is a /r/crystalgrowing subreddit with a bunch of good information, including an excellent beginner's guide.
• There's a wide variety of materials you can use which will give interesting colors and effects. Table salt doesn't work very well though.
• Growing a single crystal is harder than growing a cluster.
• Clear nail polish makes a good protective coat. Otherwise they'll dissolve over time.
• If you're impatient, you can use borax and make crystals overnight.

§ Chemical wood burning

Ammonium chloride, when heated with a heat gun, will blacken wood as if it was burned.

Notes:

• Do some test runs on wood you don't care about.
• The wood needs to be sanded smooth first.
• Some people report adding food thickener (e.g. Thick-It) to make a gel-like consistency lets them get cleaner edges.

§ Gyroscopic bike wheel

Hang a spinning bike wheel by a thread connected to only one side of its axle and it won't fall down.

Notes:

• If you've already got the bike wheel, sit on a spinning chair and rotate the wheel to spin yourself.
• You can do a simpler, less impressive demonstration of conservation of angular momentum with just a spinning chair.

§ Dish soap on milk

A drop of dish soap interacts with the fat, protein, and water in milk to push it around. A little food coloring will make the motion visible.

Notes:

• Some of the effect is from the soap disrupting the surface tension, which you can see with dish soap, water, and pepper.

§ Magdeburg hemispheres

Lowering the air pressure between two bowls relative to the outside air will seal them together.

Notes:

• The traditional version of the experiment uses a vaccuum pump and hemispheres with valves, which produces a much more impressive effect but is much harder to arrange.

§ Electromagnet

Wrap wires around around an iron core and apply a current, get a magnet. Simple and classic.

Notes:

• This video uses a giant magnet for some reason, but a 9-volt works fine..
• The more times you wrap the wire, the stronger (up to a point). You might want to use a drill or something..
• This video goes into some of the details about turns, core, and current.

§ Michelson interferometer

Split, reflect, and rejoin a laser beam, and it will interfere with itself. You can use this to measure the wavelength of the laser beam if you can move your mirrors precisely enough.

Notes:

• The kit used in this video costs >$2,500, though the company also has a cheaper one. Some people DIY it with varying complexity.
• Seeing interference should be achievable with a DIY setup if you're persistent, but measuring it accurately may not be feasible without serious making skills.

§ Barometer

Trap some air in a jar with a balloon on top and you can see relatively small changes in air pressure.

Notes:

• Put it in a hot or cold water bath to see how the air pressure changes with temperature.
• If you're going up a mountain or something, take it along and see how the pressure decreases.
• For about $10 you can get an electronic sensor (a DPS310) which can measure changes in air pressure precisely enough to measure 2cm of height difference (!!), though you'll need an Arduino or something to make use of it.

§ Lord Kelvin's thunderstorm

A clever setup with two streams of water passing through conductive rings connected to conductive basins will let you build up a surprising amount of electric charge.

Notes:

• This video gives more details about how to set it up. This one has a little more elaboration.

§ Compass

Magnetize a needle, float it on a cork, see the Earth's magnetic field.

Notes:

• The embedded video uses a paperclip, which works as well as a needle. Just make sure it's actually ferromagnetic first.
• Play around with deflecting it using other magnets.

§ Schlieren photography

See gradients in the density of air using a parabolic mirror, a point source of light, a razor, and a camera. "Seeing gradients in the density of air" is way cooler than it sounds.

Notes:

• Harvard has a good description of the procedure.
• This video also covers the procedure in more detail.
• The alignment requires a great deal of precision. The Harvard page describes it as "a bit of a bear to set up".
• If you manage to get this setup working, there's all sorts of fun follow-ons. A particularly good one is visualizing acoustic interference (note that the first part of this demo also requires a precisely tunable strobe light). Another is to look at the airstream from canned air.

§ Optical tweezers

Trap a particle of dust in a laser beam. You can move the particle around by moving the laser, even.

Notes:

• You will need a better laser than your standard pointer, and a lens to focus it. Wiring up a laser diode could be a good starter electronics project in itself.
• Be very careful with powerful lasers.
• If you get a lens with an adjustable focus, you can move the particle by adjusting the focus.
• Fun to pair with the Crookes radiometers demo above - that one purports to demonstrate that light has momentum, but doesn't really, whereas this actually does.

§ Rijke tube

Make sound by heating mesh in a pipe.

Notes:

• Metal tubes are traditional but you can do it with a cardboard tube too. Just be careful not to set it on fire.

§ Rayleigh–Bénard convection

Recreate the cell-like structure which is formed by convection on surface of the sun.

Notes:

• The video above uses graphite in cooking oil, but mica powder works well too.
• This video has a nice 2D version so you can see what's going on inside.

§ Gravitational deflection of light

Measure the effect of the sun's gravity on light during a solar eclipse.

Notes:

• I don't have a video of someone doing this, but multiple amateurs have reported success (in addition to the original in 1919, of course). See this and this. Authors are probably contactable if you need help.
• Solar eclipses are rare. If you want to do this, make sure you still take time to experience the eclipse.
• Many sources, including some which should know better, describe this experiment as proving Einstein right because it showed light bending at all. This is wrong: Newton's theory predicted that as well. But the theories produce different numbers. To do this experiment justice, you would ideally derive the numbers predicted by each theory yourself, so you could see which matches the data.

§ Woosh rocket

Ethanol vapor in a plastic bottle will make a little rocket.

Notes:

• Use something with a long handle to light it, not a match you're holding directly over or near the nozzle. And make sure to pour out the excess liquid before lighting.
• This NASA page has some nice detail.
• Also fun to do stationary (in which case it's a "woosh bottle"), which incidentally will also let you demonstrate the pressure/temperature relationship of gasses by covering the nozzle up after the reaction completes and seeing the bottle collapse.
• Apparently it is possible to get Mach diamonds in some circumstances.

§ Boil water with gravity

Lower the pressure in a tube of water enough by lifting one end 30 or 40 feet in the air, and the water will boil.

Notes:

• If you're doing this, be sure to watch the followup video which gives the whole experimental setup in more detail, including how to figure out how high you'll need to go.

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