Tag Archives: Diffusion

DIY: Diffusion Science Experiment

Have you ever stopped to notice the beauty of the swirls of color coming from a tea bag into a hot mug of water? Or had a magnificent smell of freshly baked goods waft its way over to your nose? You were experiencing diffusion. Here is a simple DIY experiment for you to try to demonstrate factors that affect diffusion.

Diffusion is the movement of a substance from an area of a high concentration to an area of low concentration. All you will need for this experiment are a few glasses of water and some food coloring. We will be looking at the diffusion of the food coloring in the water.

diffusion 1

Factor 1: Temperature

Temperature is a measure of the average kinetic (moving) energy of molecules. The hotter a substance is, the more kinetic energy it will have. If the water is hotter, it will have more energy, pushing the molecule of the food coloring more, therefore, diffusing it at a higher rate. The colder water will clearly take longer to diffuse all of the color.

Factor 2: Concentration

The rate of diffusion also depends on how concentrated the water is with food coloring. If you start off with plain water and add just a drop of color, it will take a long time to diffuse. However, if you add a bunch of food coloring, the concentration difference between the top of the glass and the bottom is much greater. This greater concentration difference will greatly increase the rate of diffusion.

Factor 3: Distance

Distance is one of the more obvious factors in diffusion rates. The shorter the distance that must be traveled, or the less volume there is, there will be a higher rate of diffusion.


Factor 4: Material

Material is another factor that might seem obvious. The lighter and small a substance is, the faster it will diffuse. On average, gases will be able to diffuse quicker than liquids which diffuse quicker than a solid. However, for our set of experiments, we are keeping the materials the same throughout.

Regardless of the factors that you manipulate, diffusion is truly beautiful to watch. So grab some food coloring and water to see it in action for yourself!

Written by: Mimi Garai


Diffusion, Pizza, and You

If you were to take a freshly baked pizza and put you and it at opposite ends of a vault with no airflow at all, would you ever be tempted by its delicious aroma? The answer, it turns out, is yes! Even without the aid of air currents, the smell would spread. Nothing in the room appears to be moving, but at the molecular level, things are very different.

At room temperature, the molecules in stagnant air whiz around at insane speeds– over 1000 miles per hour! The air seems still because molecules are so light that nobody can feel them individually, and there are approximately equal amounts of them going in every direction. However, tiny particles (like the delicious pizza odor) can still get knocked around by these randomly moving molecules. The process of stuff spreading out due to the movement of tiny molecules is called diffusion.

Molecule TempThe experiment you see in the video has one obvious difference: we are looking at a liquid instead of a gas. The molecules in water are much more tightly packed, and unlike in a gas, there isn’t as much room for them to zoom around. This means the molecules aren’t moving at such incredible speeds, but they also aren’t sitting still. They bump into one another, rotate, and vibrate like crazy!

Diffusion in ActiojnThe amount of spinning, bouncing, and vibrating that they do depends on one thing: temperature. In fact, temperature is really just a way to measure how energetic the molecules are. In the container of warmer water, the food coloring spreads more quickly. This is because at higher temperatures, the more vigorous vibrating and bouncing of the molecules pushes the green food coloring around faster. The cooler water has calmer molecules, which do less to disturb the blue food coloring.

Notice that the food coloring never seems to regroup together. Diffusion is entirely based on random movements of huge numbers of molecules, so it always results in concentrated areas of stuff like the food coloring spreading out to fill the available area. This trend towards uniform distribution is called entropy.


Diffusion causes molecules to spread out from areas of high concentration to areas of low concentration. Image credit: UC Davis

Random movement of tiny things may seem inconsequential, but it’s actually incredibly important. It’s how plants hydrate, hot chocolate cools down, spaghetti noodles absorb water, and even how oxygen gets to the bloodstream. Even more important than all of that however, is that it lets you know when there is pizza nearby!


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