How does this Science Experiment work? When you first drop the raisins in the water with baking soda, they sink to the bottom of the glass because they are more dense. But the baking soda releases carbon dioxide bubbles and these bubbles love to attach to the rough surface of the raisins. They act like tiny floatation devices that lift the raisin to the surface of the water. Once the carbon dioxide bubbles reach the surface of the baking soda water they pop and the gas is released into the air. This makes the raisins lose buoyancy and fall back down to the bottom of the glass. This continues until all of the carbon dioxide has escaped and the baking soda water is flat.