Enjoy creating make-believe potions with children this Halloween season! Give this Witches Brew Science experiment a try. Prepare one cauldron or several in a variety of colors. You can even mix in biodegradable glitter.
RELATED: Learn How to Make Oobleck
Children will enjoy discovering how base and acid reactions work through this entertaining Halloween science activity.
Looking for another enjoyable Halloween activity? Try making oobleck.
The Science
What occurs when vinegar and baking soda are combined?
You can observe the bubbling and foaming, but what produces this reaction? Baking soda (sodium bicarbonate) is a base, whereas vinegar is an acid, so the reaction you see is an acid/base reaction. At first, the mixture forms carbonic acid, which is unstable and decomposes into carbon dioxide (CO2) and water. As the gas escapes the water, it produces all the fizzing and bubbles. This bubbling reaction rises over the cauldron!
Supplies Required
- Mini Cauldrons – these are also often available at the Dollar store during Halloween season
- Baking Soda – for activities, we prefer this large 5 lb bag because it offers better value
- Water
- Concentrated Food Coloring – We prefer this liquid food coloring gel because it is concentrated and produces especially vivid colors. Regular food coloring works too; simply use additional drops for a darker shade.
- Dish Soap – any variety should be fine
- Vinegar
- Droppers or Squeeze Bottle – to squirt vinegar into the mini cauldrons
- A Tray – these plastic white serving trays are useful for messy activities or sensory play
View the Video Tutorial
Instructions
1. Place baking soda in the cauldron.
Put 1 tablespoon of baking soda into every cauldron.
2. Pour in water.
Pour 1/2 tbsp. of water into each cauldron (this helps blend the food coloring with the baking soda more easily).
3. Mix in food coloring.
Place approximately 4 drops of concentrated food coloring into the cauldron. Once blended with the baking soda, the coloring should be quite dark for a bright final effect. Regular food coloring can also be used; add extra drops to deepen the shade.
4. Pour in dish soap.
Place 1 drop of ordinary dish soap into every cauldron. This part is optional, although it makes the result somewhat foamier.
5. Pour in vinegar.
Fill a squeeze bottle with vinegar. Squeeze the vinegar into the cauldrons, and they should begin bubbling over. A small dropper or spoon may also be used to pour in the vinegar.
TIP: Mix a little water into the vinegar so you can conserve vinegar!
If the mixture does not bubble over, put another tablespoon of baking soda into each cauldron. Add a little extra food coloring to preserve the vivid color.
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