5 Fun Halloween Science Experiments for Kids to Try

Naomi Lavelle

October 13, 2021

Halloween science experiments

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Halloween is the best time of year to turn your kitchen into a science lab and have fun with lots of experiments. The more gooey, slimy and spooky the better! From glowing monster slime to screechy sounds, here are 5 fun Halloween science experiments for kids to try.

Science is so much fun for kids – it combines imagination with creativity and encourages them to develop their problem-solving and critical thinking skills. But they don’t think about that – they just want something to go boom! Hopefully that’s not the case with these Halloween science experiments, but there is definitely some oozy, gooey, gross excitement in store!

Fun Halloween Science Experiments

#1. Glowing Monster Slime

halloween slime

This is definitely, by far, our favourite Halloween experiment – just look at the photos if you need any convincing!

You will need:

  • Two small bowls or cups
  • One large bowl
  • PVA glue (white or clear if you can get it)
  • Fluorescent paint (you can get non-toxic fluorescent paint in most craft shops)
  • Food colouring (optional)
  • Something to stir or mix with
  • Borax powder (available from your local pharmacy)


  1. To the first cup, add half a cup of fluorescent paint and half a cup of PVA glue. Mix well.
  2. In the other cup, add half a teaspoon of borax powder to one cup of water and mix well until all the powder is dissolved.
  3. Now for the fun bit… pour the glue mixture into the bowl then add the borax solution, mixing all the time. After a while you can use your hands to mix and mould until you have one big lump of slime.
  4. You can store your slime in a ziplock bag or clean jar, it lasts a very long time once you do not let it dry out.
  5. If you have a UV light (black light) you can make this experiment even more fun by checking out how your slime glows in the dark once the lights go out and the UV light is turned on.

So what is the science bit?

Congratulations… you have just experimented with polymers! In simple terms, a polymer is a substance made up of lots of molecules arranged in long chains.

If you imagine that the glue is like cooked spaghetti, it slides and slips around the place quite easily. When we add the borax to the glue it causes some of the molecules in the glue to stick together, making the glue more rubbery and less liquid. Imagine if you took those strands of spaghetti and tied them together in places, the strands would not be able to slip and slide around nearly as much – the borax and glue mixture is just like your knotted spaghetti.

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#2. Fake Blood

Halloween is all about dressing up and sometimes you just need a little fake blood to really set an outfit off.

We love making our own and, with a little science knowledge, you can get just the right consistency and colour that you are after.

You will need:

  • Smooth peanut butter
  • Golden syrup
  • Washing up liquid
  • Red food colouring
  • Green food colouring


This is one of these experiments that does not come with an exact protocol, just add the following ingredients until you are happy with the appearance of it, then apply and freak out all your friends!

When you think you have the fake blood just the way you like it, do a little test on a white cloth or tissue and adjust further if necessary.

If you want to experiment a little more, try making your own fake blood choosing your ingredients from the following list:

  • Smooth peanut butter
  • Golden syrup
  • Washing up liquid
  • Red food colouring
  • Green food colouring
  • Blue food colouring
  • Chocolate syrup
  • Cornflour
  • Cocoa powder
  • Ribena
  • Chocolate syrup
  • Tomato ketchup
  • Brown sauce

So what is the science bit?

The trick to making good fake blood is to get the colour and consistency right. The food colouring, washing up liquid, cocoa powder, ribena, peanut butter and ketchup will all influence the colour of the blood. You want to get a dark, deep red colour – the chocolate and green food colouring will often give the red a darker effect.

It is not just about the right colour though, the consistency of the blood is important too. The cornflour will thicken the blood and make the colour more transparent, as will the peanut butter, syrup and washing up liquid.

The fun is in mixing and changing until you get your ideal fake blood, then apply and freak out your friends and family, all in the name of Halloween fun.


We have a frightfully fun checklist of 50 Halloween activities for Kids that you can download and work your way through!

#3. Glow in the Dark Lava Lamps

We love things that glitter and glow and this time of year allows us to really indulge this side of science. Here’s a few new favourites of ours, in case anyone wants to add some glowing fun to their Halloween parties or games!

We love making lava lamps but made a few modifications to add a bit more glow to this favourite.

You will need:

  • An empty plastic bottle or a clear plastic cup
  • Water
  • Vegetable oil
  • A funnel
  • Florescent paint (or glow in the dark paint*)
  • Alka Seltzer (or similar antacid tablets)
  • A UV light (also called a black light), if possible


  1. Put a small amount of water (about an inch or two) in the bottom of the plastic bottle or cup. Add some fluorescent paint to the water and mix.
  2. Using the funnel, pour the vegetable oil into the bottle, filling almost to the top.
  3. You will see that the water and oil settle into two layers, with the water at the bottom.
  4. Break up the Alka Seltzer tablets into smaller piece, and, if you have a UV light, turn it on and turn off the regular light.
  5. Add some pieces of the Alka Selzer tablet to the bottle to start off your lava lamp.
  6. Once the bubbles stop rising you can add more tablets to keep the lava lamp going.

This is what we did:

We had lots of different colours and types of fluorescent paint so, of course, we had to try them all! We tried both fluorescent and glow in the dark paints for this experiment and found the fluorescent paint worked best.

So what is the science bit?

The Alka Seltzer tablets drop to the bottom of the bottle and dissolve in the water.

These tablets contain an acid (citric acid) and a base/alkali (Sodium hydrogen coarbonate) in powder form. When these dissolve in water, the acid and the alkali start to react together and form carbon dioxide gas. This gas forms bubbles with the water, and these bubbles are lighter than the water and oil so they travel up the bottle to the top. Once they reach the air they burst, and the water droplet is now heavier than the oil and drops back down to the bottom of the bottle again.

#4. Oozing Pumpkins

You can’t have Halloween without pumpkins and it is great fun to carve them and cook them. You can even cover them in glow in the dark paint for an extra bit of spooky fun. Or, if you are really feeling adventurous with your Halloween science experiments, you can do this…

If you want to try this at home, we advise that an adult do the experiment!

You will need:

  • A carved pumpkin (use a small one)
  • 250mls 6% Hydrogen Peroxide
  • 2 teaspoons (or 2 sachets) dried yeast
  • 2 tablespoons warm water
  • Washing up liquid
  • Food colouring (optional)


  1. Place a small plastic container inside your pumpkin (large enough to contain 300mls but small enough to leave plenty of room between the container and pumpkin lid).
  2. Carefully pour in the 250mls hydrogen peroxide. Add a BIG squirt of washing up liquid and about 5 drops of food colouring, if using.
  3. In a separate bowl, mix the dried yeast into the warm water. Carefully add this to the hydrogen peroxide mixture inside the pumpkin, replace the lid and then stand back and enjoy!

So what is the science bit?

This is an example of a catalytic reaction, which really just means that something is added to the reaction to make it happen a lot faster, but that it is not chemically changed by the reaction. The something added is called a catalyst.

In this experiment, the yeast is the catalyst in this reaction. It splits the hydrogen peroxide into water and oxygen without getting chemically changed itself. The oxygen produced then combines with the washing up liquid to produce a LOT of foam!

Don’t Miss…

Grab the colours and get ready for a monster session of colouring! Get creative and have some fun with these Halloween colouring pages which are perfect for keeping children busy in the run up to the trick or treat excitement!

Halloween colouring pages - Mykidstime

#5. Screechy Sound Cups

This is a nice spooky science experiment. Try it out and see what kind of sounds you can make.

You will need:

  • A plastic cup
  • A paper clip
  • Some twine or string
  • A knife or scissors
  • A piece of kitchen paper
  • Water


  1. Tie the paperclip to one end of the twine.
  2. Ask an adult to make a small hole in the base of the cup, using the knife or scissors. Hold the cup upside down and thread the twine through the hole. The paperclip will stop the twine from coming all the way through.
  3. Fold the kitchen paper in half and then quarter and then dip it in water. You want it wet but not dripping.
  4. Holding the cup in one hand, fold the wet kitchen paper over the twine with the other hand and hold between your thumb and first finger.
  5. Pull the wet kitchen towel down along the twine, pinching between your fingers all the time.
  6. You should notice it makes a really spooky sound!

You can try this experiment without the wet kitchen paper, just wet your thumb and finger instead; Does it make a different sound?

You could also see what happens if you use a different type of twine, or some ribbon, or use a larger cup!

So what is the science bit?

As you pull the kitchen paper down along the twine, the friction between the two makes the twine vibrate. These vibrations travel through the air and are bounced around the walls of the upturned cup – amplifying the vibrations so we get to hear a loud, spooky, screechy sound!

5 Halloween Science Experiments for Kids to Try – Mykidstime

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