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Description

Amaze others with your ability to make a sachet of ketchup rise and sink in a bottle of water.

Resources

You will need:
Newspaper or wipe down tablecoth
Ketchup sachets
Clear plastic water bottles with caps

Instructions

Make ketchup bottles
- Split into small groups.
- The person leading the experiment should give everyone a clear plastic bottle. Everyone should fill it to the top with water.
- Everyone should fold a ketchup sachet in half lengthways and slide it into the bottle. If it sinks straight away, the air bubble inside is too small – take it out and try another sachet.
- Everyone should screw the lid onto the bottle.
- Everyone should gently squeeze the bottle and watch as the ketchup sachet begins to sink to the bottom. They should release their grip and watch it rise to the top again.
- Everyone should keep going until they’ve seen the sachet rise and sink. People could add in some drama by pretending to be a magician and commanding the sachet to rise and sink. Can anyone make their sachet float in the middle of the bottle?

The science behind the magic
- Everyone should gather together.
- Everyone should think about how the ketchup bottles worked, and people should share their ideas.
- The person leading the experiment should pass a ketchup sachet around and everyone should squeeze it gently. They should be able to move the ketchup around a little bit because there’s a pocket of air inside the sachet.
- The person leading the experiment should explain that when someone squeezes the bottle, the air in the ketchup sachet is also squeezed. It gets packed in to a smaller space, so it becomes denser and sinks.
- Everyone should think about other items that float in water. They may think of things like bath toys, sticks, ice, or wax. Everyone should try to explain why they float. The person leading the experiment should explain that items that are less dense than water float. Items full of air are usually less dense than water.
- You may want to fill a bucket of water and test people’s ideas to demonstrate the sorts of things that float.

Tags

• experiement
• experiment badge
• experiments
• ketchup

Badge Links

• Experiment - Experiment