2018By Alex SilbajorisFood coloring illustrates diffusion in water. Diffusion is the mixing of molecules due to their random motion, whether in a liquid or a gas. Because molecules in cold water have less kinetic energy than in warm water, the diffusion process is much slower than in warm water. But the food coloring can also show movement that isn't random, such as agitation of the water by convection.TL;DR (Too Long; Didn't Read)TL;DR: Food coloring added to the center of a beaker of cold water will sink to the bottom. If you stir the cold water, or add the coloring to warm water, it will diffuse much more quickly.The MECHANISM of DiffusionDiffusion does not require agitation, such as stirring, though agitation does speed the process. In the case of food coloring in water, the water is the solvent while the food coloring is the solute. Once they've mixed, they make a solution. Diffusion takes time, though how much time depends on the kinetic energy of the molecules randomly bouncing among each other. This random bouncing – called Brownian motion – results from the atoms vibrating, which they do faster and harder the hotter they are. The end result of these movements, over time, is the final, uniform solution.Mixing By Difference In Specific GravityIf not agitated, food coloring sinks in water.The food coloring has a slightly higher specific gravity, or relative density, than water, so before it has time to diffuse, it tends to sink in the water. When the water is cold, and the diffusion rate is slower, more of the food coloring stays together in a plume falling to the bottom of the container. Left alone and undisturbed, it might form a layer at the bottom; because of Brownian motion, though, there won't be a sharply defined boundary between the water and the coloring. The random motion of the molecules will gradually diffuse the color into the water. Agitation will speed the process of diffusion.Mixing by ConvectionIf the container of water is warmer or cooler than the ambient air, it will develop convective flow patterns as the water approaches the ambient temperature. In the case of cold water in a warm environment, the sides of the container conduct heat to the periphery of the water. The COOL, denser water at the center sinks. Food coloring added to this sinking center column will ride the convective flow to the bottom of the container, but then it will also ride the flow up the sides, back to the top to cycle around again. This flow serves to agitate the solution, speeding the diffusion.What Happens When the Water is Altered?Compare the effects of heat and density on the diffusion of the food coloring. Try a side-by-side comparison of diffusion in cold water and in warm water. The diffusion will be much slower in the cold water. Try dissolving half a spoonful of salt in water and then drop the food coloring. The coloring will still diffuse, but it won't sink because the saltwater has a higher specific gravity. Try placing a source of heat, such as an incandescent light, against one side of the glass, and wait a few minutes before dropping the coloring. It will ride – and thereby make visible – the convective flow. ReferencesAbout the AuthorDid you find this page helpful?Related ArticlesFrom the Web The Weird Things Only Americans Find Attractive Stop Wearing Underwear and Watch What Happens To Your Body Calypso From 'Pirates of the Caribbean' is Actually a Bombshell Here's the Real Reason Why We KissPowered by ZergNet Cartoons You Should Never Watch in Front of Your Kids This Is Why People See Ghosts, According to Science These Are the Only 3 Body Parts You Need to Wash Every Day The Tragic Real-Life STORY of the Man Who Played SlothChemistry Projects for Diffusion in LiquidsUpdated April 25, 2017By Joshua BushDiffusion is the random movement of particles, atoms or molecules from areas of higher concentration to areas of lower concentration. This process takes place in all states of matter, whether solid, gas or liquid. Several visual experiments can show you how liquids diffuse through other liquids and how liquids diffuse through membranes.Food Coloring in WaterFood coloring added to a glass or jar of water will diffuse through water until all of the water is colored. Pour water into a jar and let it sit until all movement of the water has stopped. Add the food coloring one drop at a time so you can see the drop of color slowly spread out THROUGHOUT the water. Do the same experiment with one jar of HOT water and one jar of cold water to see the effect of temperature on diffusion. If the water is still moving, another form of mixing called convection will carry the food coloring around the jar much faster than diffusion...