Step cards: bicarb soda goes in the balloon, vinegar in the test tube.
1️⃣Pour vinegar into the test tube
2️⃣Funnel bicarb soda into the balloon
3️⃣Stretch balloon over the tube
4️⃣Lift the balloon — tip bicarb in
5️⃣Watch the gas fill the balloon
6️⃣Measure it with string