3 Spooky Chemistry Experiments for Halloween Decor

Dan Wiggins

by Dan Wiggins

23rd October 2015

Whether you take halloween seriously and decorate your entire house top to bottom, or whether you have no interest whatsoever and turn the television up louder to ignore the trick or treaters, there is sure to be something in this incredible list of the 3 best chemistry experiments for Halloween props!


 1. The Vomiting Jack O’Lantern

Lets kick things off with a fairly simple experiment you can do on halloween with the most generic of halloween props… the pumpkin! This experiment is great for decorating the outside of your house, and trust me… you’ll want to keep this pumpkin outside, because it’s going to get messy! The video below shows a chemistry teacher in an unknown university explaining to his class how he can make a Jack O’Lantern appear to vomit, with the use of Hydrogen Peroxide and solid potassium iodide, or you can also use a saturated solution of potassium iodide. The reaction between these two reagents creates an almost ‘foam’ texture that expands and will push through the holes carved into your pumpkin. For a working demonstration check out the video below! You can read more about this experiment by searching “Elephant’s Toothpaste”.

2. Dry Ice Recipes!

This one is really simple and gives incredible results! You just need to be sure to take proper safety precautions, however. Including appropriate protective gloves and safety glasses. Dry ice can be obtained in almost any general supermarket, but you must be incredibly safe when handling the ice. The dry ice is solidified carbon dioxide that has been compressed and cooled in extreme environments and is 110 degrees below zero!

Halloween pumpkin with dry ice coming out of its mouthIt’s pretty well known that you can use dry ice mixed with water to create smokey effects, but did you know what else you can use with it and where around your house you can place it to create that amazing Halloween effect? The truth is, you can use your dry ice and water combinations almost anywhere! In your traditional Jack O’Lanterns, which gives an incredible bubbling effect, simply pour your water straight into the pumpkin and add your dry ice in, you’ll notice straight away the mist seeping out the holes in the pumpkin. For added effect, you can add a small amount of washing up liquid that will create a much more bubbling and violent misting effect! Another idea could be to put a coloured, waterproof tea light inside the pumpkin, and create a glowing effect!

The great thing about dry ice is you can literally use it almost anywhere (out of reach of children, of course!) One recent experiment shown how you can actually put dry ice inside of your apple juice and let it settle, once you’ve taken the dry ice out you can serve the apple juice to your guests at your halloween party and it will have created a slightly tangy and fizzy apple juice drink! Give it a try, it looks awesome as well!

3. Gooey Slime!

We’ve put together this cool downloadable instruction sheet to create your very own Gooey slime! All you need to make the slime is:

ReAgent's instructions on how to make your own gooey slime

  • Boiling Water
  • A Cup
  • Gelatine
  • Corn Syrup
  • A Teaspoon
  • A fork
  • And a spooky ghost impression… “oooohhhhh”

All you need to do is simply fill half of the cup with boiling water and add three teaspoons of the gelatine to the boiling water. You’re going to want to let it soften with a fork! Add a quarter of a cup of corn syrup to the spooky mixture! Stir it again with your fork once the syrup has been added and you should be able to see the gunk begin to form! As the mixture starts to cool down, you can continue to add small amounts of water. The fine strands of the slime are protein strands which allow the slime to stretch and make it sticky! Enlarge the infographic above by clicking on the image, right click and save to your computer to refer to later on!

For more spoooky stuff head over to my recent post “The Chemistry of Fear” and learn what is happening throughout your body when you hear something going bump in the night… Have a great Halloween! 

The chemistry of fear - Halloween science experiments


All content published on the ReAgent.ie blog is for information only. The blog, its authors, and affiliates cannot be held responsible for any accident, injury or damage caused in part or directly from using the information provided. Additionally, we do not recommend using any chemical without reading the Material Safety Data Sheet (MSDS), which can be obtained from the manufacturer. You should also follow any safety advice and precautions listed on the product label. If you have health and safety related questions, visit HSE.gov.uk.