Predict and record how much air you exhale each time you breathe out. Completely fill the bottle with water and screw the lid on.
Half fill the bucket with water.
Tip the bottle upside down in the bucket so the bottle neck is underwater. Take the lid off. Put one end of the bendable straw into the bottle neck. Take a deep breath and breathe as much air as you can into the bottle through the straw. Put the lid back on the bottle.