Old Moldy Bread
What it teaches: How fungus grows, how germs spread, environmental variables
What you need: Two types of bread (such as white and wheat), quart-sized resealable plastic bags, a spray bottle filled with tap water, tongs
What to do: As a class, discuss how people get sick or pass germs. Why is it important to wash hands? Then invite students to investigate how germs grow. Give each child one slice of each type of bread and one bag for each slice. (Note: Be careful not to touch the bread. Pass out the slices using tongs.) Have students label their bags. Ask them to gently wipe their hands on the flat surface of the bread as if they were spreading on jelly. Then lightly mist each slice using the spray bottle. Put slices into the bags and seal. Make a “control” bag by inserting a slice of untouched bread using the tongs. Place the bags in various locations in the classroom, such as the windowsill, a closet, and inside a desk. Leave bags undisturbed for three to five days. Have students retrieve their bags, and observe how their bread slices compare with the control. Record, illustrate, and discuss children’s observations. (Warning: Do not allow students to open the bags. Mold can cause eye, skin, and respiratory irritation.)
What’s going on: Mold grows from spores that are found in the air and on our skin. By rubbing the bread with their hands, the children have placed mold spores and germs on the bread. The germs and mold spores, when placed in a dark and humid environment, feed off of the sugars in the bread, and grow. This shows how germs are spread through contact, and why it’s important to maintain proper hygiene by washing hands.
What it teaches: Chemical reaction, volume, pH
What you need: Styrofoam packing peanuts, Puffins (cylindrical cornstarch-based packing material), acetone (fingernail polish remover), water, measuring cups or beakers, pH strips
What to do: Pass out one peanut and one Puffin to each student. Ask students to describe and measure the two. Which do they think is stronger? Put two cups of Styrofoam peanuts in each of two beakers. Do the same with the Puffins. Then pour one half-cup acetone and one half-cup water into separate cups. Have students measure the pH level of each liquid. Which liquid do students think will cause a physical change in the peanuts and Puffins? Pour the water into one of the peanut beakers. What happens to the Styrofoam? Next, pour the acetone into the second peanut beaker. What happens now? Ask students to observe any physical changes that occur and to measure and compare the volume of peanuts in each beaker. Repeat, using the Puffins.
What’s going on: Puffins are a biodegradable packing material made from blown cornstarch. Any liquid will cause a physical change in the cornstarch, dissolving the Puffin. Only acetone will cause a physical change that “melts” and releases captured air from the Styrofoam peanuts.
Garbology: Whose Trash Is It?
What it teaches: Principles of archaeology, critical thinking
What you need: Five paper grocery bags, various pieces of clean trash (no discarded food items)
What to do: To prepare for this activity, gather clean items of trash and sort them into themed bags, such as a “junk-food bag” with Doritos and Snickers wrappers, and a “pet-friendly bag” with cat-food cans, receipts for vet bills, etc. Then divide the class into small groups, and give each group a bag of trash. Ask students to pull out one piece of trash at a time and record each item and how it was used. When the bags are empty, have groups look at their findings and develop a hypothesis about the people to whom the trash belongs. Invite students to present their findings.
What’s going on: Garbology is a relatively new form of science that began in the 1970s at the University of Arizona. It’s based upon principles found in archaeology which suggest that evidence and patterns about people’s lives can be found in their garbage. Excavations of artifacts from buried trash pits and modern-day refuse dumps give archaeologists clues to the items people use, their diets, and culture.
Wet Diaper Science
What it teaches: Polymers, absorption
What you need: Diapers, resealable plastic bags, clear plastic cups, plastic teaspoons, water, blue food coloring
What to do: Show students a diaper. Once the giggles subside, ask them to guess how much water they think the diaper can hold, and record their responses. Invite small groups to cut out the waist and leg bands of a diaper and place the remainder in a bag. Separate the layers of the diaper and seal the bag. Shake the bag for two minutes. Kids will see a dry powder resting at the bottom. Have them remove everything from the bag except for this powder. Pour the powder (sodium polyacrylate) into a cup. Ask students to pour four ounces of water into a separate cup and add four drops of blue food coloring. Slowly spoon water into the cup with the powder, keeping track of the amount as you go. How does the powder change? (It should now be a gel.) Challenge students to predict how much more water this gel can hold. Continue to add spoonfuls of water, keeping track of the amount of water added and recording observations along the way, until the water no longer soaks into the gel. Ask students to determine how much water the powder can hold.
What’s going on: Sodium polyacrylate is a super-absorbent polymer that absorbs up to 300 times its weight in water. It is used in baby diapers to keep wetness away from a baby’s skin. This polymer is also used as a soil substitute.
What it teaches: Polymerization, physical properties
What you need: One cup whole milk, two tablespoons white vinegar, hot plate, strainer (makes enough for four students but can easily be doubled)
What to do: Warm the milk in a pan, but do not boil. Remove the pan from the heat and slowly stir in the vinegar. Continue to stir until a white rubbery substance forms in the liquid. Strain the liquid from the rubbery substance. If you’ve done the diaper experiment, kids may correctly guess that they have created a polymer. Divide the polymer among students and ask them to gently pat and roll it to remove any remaining liquid. Test its physical properties. Kids will discover it stretches, bounces, and sticks to a surface.
What’s going on: This is a very nasty-tasting, yet edible, experiment. Cow’s milk is loaded with the polymer casein, a protein. Without this polymer, cheese would come unglued. The casein is suspended in milk, but the vinegar causes cross-linking of the casein chains, resulting in visible clumping of the polymer. Casein is used in some glue. Without casein, glue would come unglued too.