Underwater Fireworks      Investigate diffusion by creating underwater fireworks using food coloring, oil and water      Cooking oil Box of food coloring (with green removed) Water Clear empty soda bottle Plastic cup Fork Tablespoon      1. Place a few tablespoons of the oil into the plastic cup. 2. Add 4 drops of red, 4 drops of blue, and 4 drops of yellow food coloring to the oil. 3. Use the fork to mix the oil and colors together so that the color drops break up into smaller ones. Try not to let the color drops mix together. Why do you think the colors don’t dissolve into the oil? 4. Fill the soda bottle nearly to the top with water. 5. Carefully pour the mixture of oil and food color into the water in the bottle. 6. Observe the bottle closely, but do not move it around or shake it.      When you put food coloring in the water, it begins to spread out. This process is known as diffusion. Diffusion is simply the motion of molecules from an area of high concentration (where there is a lot of food coloring) to an area of low concentration (there is very little food coloring). The coloring will continue to spread out until the same amount is found all through the water. Because the food coloring is first mixed with the oil, and oil does not mix with water, the coloring does not immediately mix with the water. It takes a few minutes for the food colors and the oil to separate. Since the water is not being shaken or stirred (you are just observing here), the mixing of the colors with the water happens by diffusion.      For Younger Children When adding to the food coloring to the oil, you can add two colors instead of three and have the children mix two colors and predict what the final color will be. You can talk to the children about primary and secondary colors as they make predictions and set up their projects. For Older Children When doing this activity the focus could be more on the differences between the oil and the water and their interactions. They can test other liquids that don’t mix with water, such as rubbing alcohol and see if the experiment works with the other liquid. Another variation would be to see if the sizes of the food coloring drops affect the rate of diffusion. Children could use a stopwatch to time the rate of diffusion.      http://www.west.asu.edu/achristie/548/02WQ/robbin/index8.htm http://www.channel4.com/learning/microsites/C/ clipbank_marketing/sci/taster/sci0243130404.html