Introduce the concept of microorganisms, also known as bacteria, by showing kids how it grows. Bring two loaves of bread to your classroom. Ensure that one is properly sealed so that no air is allowed to make its way inside the bag of bread. Leave that out for a demonstration. Next to it, place an additional loaf of bread that has a pin-size hole in the plastic. Over a short amount of time, the second loaf of bread will begin to grow mold. The kids can see the physical evidence of how this form of bacteria comes to be.
Students can analyze the cleanliness of their own classroom by taking samples and testing them in petri dishes. Provide each student an assigned location in your classroom. If necessary, expand the locations to other areas within the school. Give each student a cotton swab and have them swab their designated area. Gently rub the swab over the petri dish. Put the lid back on and seal it shut. Keep all of the dishes on a table that either gets consistent sunlight or is in a warm area. After two to three days, have the students look at their petri dish and examine if bacteria is growing in the dish.
Show students the difference between unwashed and washed hands with a group classroom activity. Have one student shake hands with every student in the classroom. After this first phase of the activity, swab the student's hands with a cotton ball and then swab a petri dish. Instruct the student to then wash his or her hands and upon drying, immediately swab their hand in the same place as the previous sample. Put that on a different petri dish and leave both in a warm area for two or three days. Have students examine the growth of bacteria on both plates to see how germs can live on our skin.
With bacteria from samples that were either collected from the classroom experiment or the hand-washing experiment, draw up a small amount from the petri dish and place it on a slide. Set up a microscope so that students can take turns looking at the magnified bacteria to see what it looks like on a cellular level. After viewing the bacteria on the slide, kids can then draw the bacteria cells on their own.