This experiment requires only three balloons and a little perfume. Blow up each of the balloons and squirt perfume into each before knotting it. Spray the inside of one balloon with one squirt of perfume, one balloon with four squirts and one balloon with eight squirts. Label the balloons with the number of squirts to avoid confusion. Record the amount of time it takes to smell the perfume outside the balloons. The balloon with the highest concentration gradient, eight squirts of perfume, will have the fastest rate of diffusion. The cause of diffusion in this experiment is a concentration gradient, which causes the molecules to flow until equilibrium is reached.
For this experiment, you need six clear plastic cups. Fill the first three cups with cold water. Add a drop of blue food coloring to one cup, red food coloring to one cup, and yellow food coloring to one cup. Allow the children to watch the colors diffuse throughout the water. Use a stopwatch to record how long it takes the colors to completely diffuse in each cup. Fill the next three cups with hot water and repeat the experiment. Compare how long it takes the colors to diffuse in hot water compared to cold water. Discuss how an increase in temperature increases the kinetic energy of the molecules and speeds the rate of diffusion.
This experiment requires a little preparation, but the whole class will enjoy it. Gather various things that have a strong smell, such as vanilla candles, coffee beans, rosemary, popcorn and pizza. Have the students form a line from the front of the classroom to the back. Have them put on blindfolds. Introduce the smells one at a time, and ask the students to announce out loud when they smell the item. Use a stopwatch to record the time it takes the smell to reach each student. Once the scent has traveled halfway down the line, place a fan behind the smell. Continue to record the time it takes the remaining students to smell the item. After the smell has diffused to the last person in line, introduce a new smell, following the same procedure of introducing the smell without the fan and then turning the fan on. Compare the rate of diffusion without the fan verses the rate of diffusion with the fan. Discuss how the increase in kinetic energy increases the rate of diffusion.
This experiment is more appropriate for middle and high school students who are studying osmosis along with diffusion. Prepare by boiling two eggs and bringing them to class. Place the two eggs in a jar of vinegar for one week. The vinegar will decompose the egg shells and leave the membranes behind. Some of the vinegar will diffuse from the higher concentration in the jar to the lower concentration in the eggs, causing them to swell. Remove the eggs and measure the circumference of each. Place the eggs in two separate glasses. Fill one glass with pure honey. Fill the other half with honey and half with water. The next day, measure the circumference of the eggs again. The egg in the glass of pure honey will have shrunk more than the egg in the half honey and half water solution. This is because the rate of diffusion and osmosis is greater when there is a greater concentration gradient.