Fizzy Christmas trees with baking soda

The holiday season is always a fun time to try new science activities and experiments. Some of our personal favourites are coffee filter Christmas trees and DIY paper Christmas lights.

We’re also certain you can never go wrong with making some classic paper snowflakes (an awesome way to teach the concept of symmetry!) or using a foolproof salt dough recipe to make some salt dough Christmas decorations.

But it doesn’t hurt to shake things up by trying something new, right?

We recently discovered this fun melting Christmas tree activity by Natalie from Raising Little Kings and we’re already obsessed!

We are absolute suckers for baking soda and vinegar experiments, and this cool Christmas-themed one has an exciting icy twist!

fizzy christmas trees science activity

What you need to make melting trees

For this activity, you really don’t need many ingredients at all. The most important item needed is a Christmas tree mould or cookie cutter that you can use to create the tree shape.

Alternatively, if you’re feeling adventurous, you can try to make the shapes yourself by moulding the baking soda mixture with your hands or modelling tools. 

Another way to do this activity if you don’t have a Christmas tree-shaped mould to hand is to change the shape to another seasonal object.

For example, you can use circular cookie cutters to make little melting snowmen, star-shaped ones to make fizzy Christmas stars and so on.

We actually did our own variation on this preschool Christmas science activity in our popular kids’ activity book Fun at Home with SUPA STEM.

We made snowmen that fizzed and bubbled as they melted – pretty cool!

With 21 awesome activities inside, this 32-page eBook is currently available for FREE here – so don’t forget to grab yours!

Now let’s get into the ingredients!

To do this Christmas tree science experiment, all you need is:

  • Christmas tree or other shaped mould (or cookie cutter)
  • Baking soda (bicarbonate of soda)
  • Water
  • Food colouring (green for trees, or whichever colour suits your chosen seasonal shapes) – you can skip this if you are going to make something white like snowmen
  • Vinegar
  • Droppers, spoons or small squeezy bottles

Read on to find out how to use these simple household items to do this Christmas chemistry experiment!

christmas science activities for preschoolers

How to make fizzy Christmas trees

One of the best things about this activity is it can be prepared in advance, left in the freezer and brought out whenever you need to fill a few hours on a rainy (or snowy) day.

Here’s how to set up the experiment:

  1. Mix baking soda, water and food colouring together to create a mixture. You can eyeball this, but make sure it’s mostly baking soda as there won’t be as much fun fizzing if the mixture is mostly made of water.

    However, if the mixture is too thick and dry it will be more difficult to mould and won’t freeze as well, so play about with it until you’re happy with the consistency.

    Just a few drops of food colouring is usually enough per mould. 
  2. Add the mixture to the moulds and freeze overnight. You can then leave them in the freezer until you’re ready to do the activity with your kids!

How to do this Christmas tree science activity with kids:

  1. Remove the Christmas trees from their moulds and place them in a large waterproof dish or bowl. 
  2. Add vinegar to a squeezy bottle or pour a small amount into a cup.
  3. Kids can use the squeezy bottle or a spoon/dropper to slowly add the vinegar to the Christmas trees. 

***Safety Note***

Vinegar is acidic and should be used carefully. We always recommend protective clothing, including eyewear, and kids should wash their hands thoroughly afterwards.

The baking soda and vinegar reaction will cause bubbles so particular care should be taken to protect eyes and not to get too close.

Doing this melting Christmas trees activity with kids of all ages

If you’re planning on trying out this Christmas science experiment with preschoolers and young children, make sure they are old enough and responsible enough to wear protective clothing and take sensible precautions. 

It goes without saying that they should be way past the mouthing stage. 

Baking soda and household vinegar are usually both pretty harmless in small amounts, but kids still need to be closely supervised throughout this activity (see safety note above).

Younger children will enjoy seeing the reaction occur and noticing sounds, sights and smells. Be sure to ask them questions like ‘what can you see?’, ‘what is happening to the trees?’, ‘what can you hear?’ and even ‘what can you smell?’

For older children, they may be able to try to explain what is happening when the vinegar is added to the baking soda. See if they can make predictions in advance about what will happen, and explain why bubbles appear. 

The science behind this fizzy Christmas tree science activity

Here’s a simple explanation of the science behind this cool activity.

Baking soda is a base that reacts with acids like vinegar. On the pH scale, that measures how acidic or basic a substance is, they are more or less opposites. 

That means that when they come into contact with each other, a chemical reaction takes place.

They both change chemically, and a lot of gas is formed. This gas is carbon dioxide – the same gas used to make the bubbles in fizzy drinks!

As carbon dioxide is produced, it makes bubbles that fizz and pop. Pretty cool, right?

We hope you loved this example of the many awesome science Christmas activities that you can do during the holidays. 

A huge thanks to Natalie from Raising Little Kings for sharing this with us – you can see more of her brilliant activity ideas for kids here.