Bottle Balloon in Hot and Cold Water

Balloon inflates in warm water and shrinks in cold. Ask students to predict what will happen. Fit balloon over bottle; move bottle between warm and cold water. Key idea: Warm air expands and cool air contracts. Ask: What changed if we didn't blow into the balloon? Safety and cleanup: Warm—not hot—water; plastic bottle. https://www.google.com/search?q=%22Bottle%20Balloon%20in%20Hot%20and%20Cold%20Water%22%20science%20demonstration%20experiment