Did you know you can blow up a balloon without touching it? I’ve added a little Halloween twist to this activity by turning the balloon into a pumpkin!
Imagine a row of these in your window to greet trick or treaters!
What you need to blow up a pumpkin balloon
Small bottle
Alka seltzer
Water
Orange Balloon
Black Sharpie
Method
Blow up the balloon first and then let the air out, draw a pumpkin face on the balloon.
Half fill your bottle with water.
Drop an alka seltzer into the bottle and place the balloon on top.
Watch as the balloon blows up and your pumpkin grows.
Why does this happen?
Alka Seltzer contains contain sodium bicarbonate ( baking soda ) and citric acid. When placed into water it forms sodium citrate, water and carbon dioxide which are the bubbles of gas you see. The gas fills the bottle and then the balloon forcing it to expand!
The bicarbonate of soda reacts with the citric acid, this is an acid – base reaction just like we see when we add vinegar to baking soda.
Acid–Base Reactions
If you place an acid and a base together, they react to neutralise each other, producing a salt. The H(+) cation of the acid combines with the OH(-) anion of the base to form water.
Extension Ideas
Can you compare the alka seltzer with an effervescent vitamin tablet? Which blows up the biggest balloon? Think about how you can make this a fair test.
You could also try popping candy or baking soda and vinegar.
More Halloween Science Activities
Try our spooky STEM Challenges for Halloween
Are you having a Halloween Party? We’ve got some creepy ideas to start the party with a bang.
Steam Powered Family have a brilliant pumpkin battery investigation too!
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