Ward's World Activity Guides

Page 2 Part B. Prepare a germ solution: 1. Add approximately 1 oz. (about 2 tablespoons) of yogurt or soil to about ½ cup warm water and gently mix until dissolved. 2. Put this solution into a clean spray bottle labelled "GERMS." Your solution contains harmless germs that will serve as living indicators to show how a face cloth prevents microscopic drops from spreading after a sneeze. Part C. Prepare the test boxes: 1. Use the cereal box with windows from Experiment 2. Remove the cloth from the previous experiment and set aside. 2. Prepare a covered container ready to put the gelatin growth plates in, after they are sprayed, such as an uncut cereal box. Alternatively, a large zip-top bag over a clean plastic storage container can be used. This will be your germ-growing container. Part D. The Experiment: 1. While conducting the experiment wear a FACE COVER so you do not accidentally contaminate the plates. DO NOT touch the prepared gelatin with your fingers (this could contaminate them!). 2. Prepare 4 gelatin growth plates to test the effectiveness of cloth face covers. Label the plates as #0: (no cover), #1: (1-layer), #2: (2-layers), and #3: (the face cover you have been using). You will test 2 layers of cloth first. 3. Fold a piece of cloth in half. Cover the box window with 2 layers of cloth—use masking tape to help keep it in place. 4. Turn the box flat so that the cloth-covered window is facing up. Place plate #2 in the box, under the covered window. 5. From about 5" away from the cloth, at about a 45° angle, spray TWICE into the window. Wait 30 seconds for microdroplets to land, then carefully slide the plate out of the test box into the germ growing box—be sure not to touch the gelatin! 6. Remove the cloth from the box. Wipe the test box with tissue and dispose of the tissue but save the box for the rest of the experiment. 7. Repeat steps 2–6 using a. 1 layer of cloth (plate #1) b. your own face cover (plate #3) c. no cover (plate #0) 8. Close the germ growing container. Leave it in a warm place where it can stay undisturbed but observed for a few days (on top of the refrigerator works well). 9. Dispose of the box, used cloth, and tissues carefully. Clean the working area and wash your hands thoroughly. Check the gelatin plates after 24 hours. Remember to wear your cleaned face cover and wash your hands before checking the plates. Count the number of spots (colony forming units or CFUs) that have formed on each plate. If possible, leave the plates in container during observation. Do NOT touch the surface of the plates! Finish: 1. Record your data in the table. 2. Wash your hands after observing the plates. 3. Repeat the observation after 48 hours. Record the number of Colony forming units (CFU). 4. Dispose of the germ plates in the trash, wash the area thoroughly and finally re-wash your hands. 5. Share your data: enter the results of Column G in the form here: https://forms.gle/Da1ozBnbn9ShkVESA How many germ-carrying droplets can cross cloth? (continued) + ward ' s science

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