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Diffusion & Convection Chemistry Experiments

Convection is the flow of molecules within a fluid. Diffusion is the spread of particles from areas of higher density to areas of lower density until equal density is achieved, as when ink spreads through water. These experiments will help students visualize and understand the processes of convection and diffusion.

Dye Diffusion
- A great way to help children visualize diffusion is to put drops of food coloring into water. Set up several clear containers of water and let children watch as you put one color of food coloring into each, or let them put in the food coloring if they are old enough. The color should start out dense at the top and diffuse slowly throughout the water in random patterns. Children can experiment further by mixing the colors together slowly or quickly in various quantities.
Egg Osmosis
- This experiment is for more advanced chemistry students. Soak an egg in vinegar for a few days until its shell is soft. This dissolves the calcium in the eggshell and turns the shell into a semiporous membrane. Measure the circumference of the egg, then soak it in corn syrup for a few days. Water will diffuse out through the porous shell and the egg will shrink. (The sugar molecules in the corn syrup are too large to fit through the shell.) Soaking the egg in water will return it to its original size or more.
Convection in Bottles
- This is a very simple experiment in convection that even small children can enjoy and participate in. Fill a clear plastic bottle all the way to the top with hot water from the faucet and dye the hot water with food coloring. Fill another bottle to the top with cold water and turn it upside down over the first bottle, holding the necks together tightly. The cold clear water is denser than the warm dyed water, so the warm water will flow upward, creating a visible convection effect.
Pen Chromatography
- This experiment uses diffusion to create a visual breakdown of the different components in marker dyes. Draw dots along the bottom of a paper towel with different colored markers. The dots should be roughly 1 cm wide, 3 cm apart and 1 cm from the edge of the paper. Pour about 2 cm of water into a glass and stir in a teaspoon of salt, then loosely roll the paper towel and put it into the water, marked edge down. As the water soaks up the paper towel the marker colors should diffuse and separate into their component colors.

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