Diving Ketchup Cause a packet of ketchup to rise and fall on command. email to friend
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1. First, you'll need to perform a œfloat or sink test to see how the ketchup packet works. Fill the bowl with water and drop the packet into it. If it floats, great! If it sinks to the bottom, no sweat. This shows that atmospheric pressure in the packet is pressing hard enough on the air bubble inside the packet to sink it. If this happens, you get to make more trips to your favorite fast-food restaurant to find a ketchup packet that just barely floats!

2. Scrunch the packet in half lengthwise and carefully push it into the soda bottle. Fill the bottle full to the brim with water and screw on the cap. Squeeze the sides of the bottle and hold the squeeze to make the packet sink. Let go and it rises.

How does it work?

The packet floats because an air bubble gets trapped inside the packet when it's sealed at the factory. If the packet sinks when you test-float it, then the air bubble is too small to make it float. That's the easy part.

As you squeeze the bottle and push the water against the floating packet, you compress the air bubble into a smaller space. This happens because gases are more œsquishable than liquids. When you decrease the volume (making the bubble of air smaller), you increase the density of the packet and it sinks! When you release the pressure on the bottle, the compressed air expands inside the packet and the diver floats to the top of the bottle.

Additional Info

Learn how to make a classic Eye-Dropper Cartesian Diver.