What conditions affect the diffusion of a substance in water?
Have you ever colored a picture with marker and noticed that two touching colors begin to bleed together? In class, do you typically sit evenly spaced or all scrunched together? Although one of these refers to chemical properties and the latter social interaction, both are examples or diffusion.
Diffusion is the mixing of substances due to the movement of their particles. This can occur with all sorts of matter, but is most commonly observed in liquids and gases. Typically, diffusion refers to the movement of molecules from high concentrations to lower concentrations. The rate of this movement depends on the energy of the molecules. Think of how delicious smells from your kitchen take longer to get into your bedroom than to your living room which is located right beside the kitchen. That is because the molecules from the food odor haven’t diffused into that space yet. In this experiment, you will experience how temperature affects the mixing of food coloring drops with water.
In this experiment, the food coloring that gets added is the same temperature in each of the hot and cold water tests. Do you think the temperature of the food coloring might have an effect on how it diffuses? Can you find a safe way to heat or cool the food coloring before adding it to the water? Can you predict, based on the first way of doing the experiment, what might change, if anything?
Also, think about where you see this happen in other places. For example, how might this play into why coffee and tea always start with hot water? If you find an example of where hot or cold water is used for something that might involve diffusion, see if you can try it with the opposite and observe any differences in the results.
This experiment was selected for Science at Home because it teaches NGSS Disciplinary Core Ideas, which have broad importance within or across multiple science or engineering disciplines.
Learn more about how this experiment is based in NGSS Disciplinary Core Ideas.