Key Concepts
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Diffusion -
Temperature and Molecules
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Introduction
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.
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Background
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.
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- An adult helper
- Two clear glasses
- Water
- Food coloring
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Preparation
- Fill one glass half full of the coldest water you can get from the tap
- Fill the other glass the same amount with the hottest water you can get from the tap
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Procedure
- Make a prediction. What might be different about the way the food coloring moves through the cold water and the hot water?
- At the exact same time, add 2-3 drops off food coloring into each glass. Do not mix or stir.
- Watch what happens to the food coloring. Does it move differently in the hot water than the cold water?
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Observation and Result
The food coloring mixes through the hot water faster than it mixes with the cold water. This is because in hot water, the water molecules have more energy and are moving faster than the molecules of cold water. This makes it easier for the dye to get mixed throughout the hot water. Because diffusion happens from high concentration to low concentration, the more molecules are moving, the more opportunities they have to mix together. The high energy hot water model diffusion is important because it’s how we get oxygen to all the cells in our bodies. When deoxygenated blood is in your capillaries in your lungs, the oxygen in your lungs diffuses from a higher concentration in your lungs to the lower concentration in your blood. This allows red blood cells to carry oxygen all over your body. -
Clean Up
Be sure to clean up when you are done. Wipe up any spills that may have happened. Pour all of the water down the sink, and wash out the glasses. Put the food coloring back where you found it. -
More to Explore
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.
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Safety First & Adult Supervision
- Follow the experiment’s instructions carefully.
- A responsible adult should assist with each experiment.
- While science experiments at home are exciting ways to learn about science hands-on, please note that some may require participants to take extra safety precautions and/or make a mess.
- Adults should handle or assist with potentially harmful materials or sharp objects.
- Adult should review each experiment and determine what the appropriate age is for the student’s participation in each activity before conducting any experiment.
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