Top 3 Science Experiments for Primary School Assemblies


Are you the science co-ordinator in a primary school? Looking for some fun experiments to do in a science assembly for Ks1, KS2 or the whole school? We have collected our top 3 science experiments which are visual, fun and perfect for primary school children. These experiments make great interactive demonstrations with changes to pick volunteers as assistants. Best of all, these experiments are all simple and easy to do with equipment that you can pick up cheaply in the supermarket.

If you are based up to 35 miles from one of our UK branches you can even book one of our scientists to come in and run the assembly for you – completely free of charge! Click here to find your nearest branch or read on to find out how to do our top 3 science experiments for primary school assemblies.

Dancing raisins

This experiment is very visual, easy to perform and works every time! This experiment takes around 5 minutes.

You will need

  • 1 cup raisins
  • White vinegar or citric acid
  • Bicarbonate of soda
  • Large jar or clear bowl
  • Tray
  • 1 cup

Fill your glass/bowl 2/3rds full of water before starting the assembly. Hold up the glass/bowl of water and tell the children what it is. Ask them if any of them have ever heard of the word ‘acid’. Explain that you are going to make the water slightly acidic by adding something called citric acid/vinegar. Add 2 – 3 teaspoons of citric acid or 1 cup vinegar to the water.

Next, explain that you are adding something strange – raisins! Add a handful of raisins. Ask for a volunteer and have them come to the front to be your assistant. Ask the children if they know the opposite of the word acid (alkali or base). Explain that you have an alkali with you called bicarbonate of soda.

Hold up the glass/bowl over the tray, have the children all count down from 5 then have your assistant tip a cup of bicarbonate of soda into the glass/bowl. The mixture will fizz and bubble and hopefully overflow! As it settles down the raisins will be moving around.

Let the assistant sit back down (give them a clap) then explain that you have created carbon dioxide gas which made the mixture bubble. The carbon dioxide also clings to the rough surface of the raisins and makes them float. Compare this to wearing a rubber ring in the swimming pool.

Elephant’s toothpaste

Elephant's toothpaste makes a great experiment for a primary school assemblyThis experiment is always a crowd pleaser – so named because it makes loads of foam that looks like it could be used to clean the teeth of an elephant! This experiment takes around 5 minutes.

You will need

  • Plastic bottle
  • Hydrogen peroxide (6% or 9%). You can buy a 300ml bottle from most pharmacys
  • Dried yeast
  • Washing up liquid
  • Tray
  • Cup (pre-filled halfway with warm water)
  • Spoon

Explain that in this experiment,  you will be making a gas called oxygen. Hold up your bottle of hydrogen peroxide and tell the children what it is. Explain that the more you use, the bigger the reaction will be. Ask the children if
they want a little bit or a lot (they will choose a lot!) Gradually pour the hydrogen peroxide into the plastic bottle, continually asking the children if they want more and building up excitement until you have poured in the whole bottle.

Add a squirt of washing up liquid ‘to make it extra bubbly’. In a separate cup mix up 1 teaspoon of yeast with half a cup of warm water. Have a child come and be your assistant. The other children should count down ‘5,4,3,2,1’ and then the assistant can pour the yeast mixture into the plastic bottle.

Let the assistant sit back down (give them a clap) then explain that you have created oxygen gas which got trapped in the washing up liquid and made the mixture bubble out over the top of the bottle.

Colour changing cabbage water

This experiment is great for a really big group of Key Stage 1 or Key Stage 2 children (or both!) and looks so cool it’s almost like magic! This experiment takes around 3-5 minutes.

You will need

  • Red cabbage
  • White vinegar
  • Bicarbonate of soda
  • Clear cup, bowl or jar
  • Spoon
  • Tray
  • Additional cup

You will need to make cabbage water in advance by chopping up a red cabbage and boiling it. Sieve out the cabbage and keep the water that should now be blue/purple.

When you get to the assembly, fill the clear cup, bowl or jar half way with cabbage water and tell the children what it is or get them to guess. Ask them if any of them have ever heard of the word ‘acid’. Hold up your vinegar and explain that it is an acid. Have a volunteer come up and pour a little vinegar into a cup for them. The children can all count down 3,2,1 and then the assistant can pour the vinegar into the cabbage water. It will go bright pink!

Ask the children if they know the opposite of the word acid (alkali/base). Explain that you have an alkali with you called bicarbonate of soda. Put a little bicarbonate of soda into the cup and then the children can all count down again – 3,2,1 and then the assistant can pour the bicarbonate of soda
into the conical flask. The mixture will go blue, fizz and bubble and hopefully overflow! Let the assistant sit back down (give them a clap) then explain that you have created carbon dioxide gas which made the mixture
bubble. Also, the alkali makes the cabbage water go blue again.

Good luck with your science assembly. We offer lots of free advice and resources for science teachers. If you would like to be added to our mailing list to receive more experiments, please fill in the form below. We will never pass your details to any 3rd parties and you can unsubscribe at any time.

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