Why do food coloring move in water?

The movement of food coloring in water is caused by a process called diffusion. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. In the case of food coloring, the molecules of the food coloring are more concentrated in the drop of food coloring than they are in the water. Therefore, the molecules of food coloring will diffuse from the drop of food coloring into the water until the concentration of food coloring is the same throughout the water.

The rate of diffusion is affected by a number of factors, including temperature, concentration, and surface area. Temperature affects the rate of diffusion because higher temperatures cause molecules to move more quickly. Concentration affects the rate of diffusion because the higher the concentration of a substance, the more molecules there are to diffuse. Surface area affects the rate of diffusion because the greater the surface area, the more molecules can diffuse at the same time.

In the case of food coloring, the rate of diffusion is increased by stirring the water. Stirring the water causes the molecules of food coloring to move more quickly and it also increases the surface area of the water, which allows for more molecules to diffuse at the same time.