Paper Won't Enter the Bottle

The ball often pops back toward you instead of going in. Ask students to predict what will happen. Place the ball at the mouth and blow straight into the bottle. Key idea: Air already inside the bottle must escape and pushes back. Ask: Why can't the paper simply move into the bottle? Safety and cleanup: Use clean individual paper ball; no sharing bottle mouth. https://www.google.com/search?q=%22Paper%20Won%27t%20Enter%20the%20Bottle%22%20science%20demonstration%20experiment