1. Racing Raisins

2. What you need  one package of raisins  a large beaker (800ml)  carbonated water  stop clock

3. What to do  participants are invited to choose a raisin to drop into a large beaker of carbonated water  time how quickly the raisin sinks and rises back to the surface  participants are required to race with each other  observe the bubbles forming on the food surface during the experiment

4. What to do  prizes are awarded to the top three fastest times  special prizes will be given to participants who enable to explain the scientific reason behind

5. What is happening  a raisin is denser than water so it will initially sink  carbonated water contains carbon dioxide bubbles  rough surface creates a large surface area for the bubbles to attach to  the number of bubbles increases on the raisin, raisin and bubbles become less dense than water, and rise to the surface

6. What is happening  once it has risen to the surface, the bubbles burst, releasing the carbon dioxide into the air  raisin sinks again  therefore, the items that work best will have a density that is only slightly greater than that of water