Hooked on Science: Sound of gas

Materials

• Two empty water bottles
• Water
• Alka-Seltzer

Instructions

STEP 1: Fill each of the bottles less than 1/4 of the way with water.

STEP 2: Blow across the top of the bottles and observe.

STEP 3: Add two Alka-Seltzer tablets to one of the bottles and observe.

STEP 4: Blow across the top of the bottles and observe.

Explanation

The sound is different as you blow across the top of the bottle with the added Alka-Seltzer. Carbon dioxide gas is produced as a result of a chemical reaction between the water and Alka-Seltzer. Sound travels more slowly through the carbon dioxide gas than through the air; therefore, when you blow across the bottle with the added Alka-Seltzer, you hear a lower-pitched sound.