Vinegar and baking soda mix together in the jar and release carbon dioxide gas. That gas forms tiny bubbles on the wrinkled surface of each raisin and carries it upward. Once a raisin reaches the top, the bubbles pop and it sinks again — then the cycle repeats as long as the mixture keeps producing bubbles.

Density decides whether something floats or sinks. A raisin is denser than the liquid, so it sinks at first. Then tiny gas bubbles form on its wrinkled surface and cling there, making the raisin less dense overall. The bubbles act like tiny floats, carrying it upward. Once it reaches the top, the bubbles pop and the raisin becomes dense again — it sinks, and the cycle repeats.

When you drop raisins into a fizzy mix of vinegar and baking soda, they sink at first. Then tiny gas bubbles form on their wrinkled surface. As those bubbles collect, they carry each raisin upward. At the top, the bubbles pop and the raisin sinks again. The cycle repeats as long as the mixture keeps producing bubbles. All you need is a glass jar, vinegar, baking soda, tap water, and a handful of raisins.