Breaking the Tension
Preschool–Kindergarten
These simple activities demonstrate surface tension.
What You Need
★ Index card
★ Safety scissors
★ Sink filled with water
★ Glass half filled with water
★ Liquid dishwashing detergent
★ Ground pepper <!>
★ Toothpicks
What to Do
★ From an index card, cut out a boat shape, like the one on this page. Make the boat about 2-1/2 inches long and 1-1/2 inches wide. Have your child place the boat gently on the water in the sink. Have him pour a little detergent at the notch end of the boat. Ask him to describe what happens. (Note: To repeat this experiment, you’ll need to use fresh water to make the boat move.)
★ Next, sprinkle a little ground pepper on the water in the glass. Give your child a toothpick and tell him to dip it in the middle of the pepper. Ask him what happens. Then tell him to put a drop of the detergent on another toothpick and dip it into the pepper. Now what happens?
Surface tension results when the hydrogen in water molecules stick to one another as well as to the water below them. This creates a strong but flexible film on the water’s surface. The detergent disrupts the molecules and “breaks the tension,” making the boat go forward and the pepper move to the sides of the glass.
Bubbles
Preschool–Kindergarten
Children can learn more about surface tension and about change just by blowing bubbles!
What You Need
★ 8 tablespoons of dishwashing liquid
★ 1 quart water
★ 1 drinking straw
★ A shallow pan
What to Do
★ Mix the dishwashing liquid with the water and pour it into the pan. Give your child a straw and tell him to blow through it as he moves it slowly across the surface of the solution. Ask him to notice the size of the bubbles that he makes.
★ Next, have your child try to make a very big bubble that covers the surface of the pan. Have him do the following:
—Dip one end of the straw into the solution. Then hold the straw slightly above the surface. Blow into it very gently. He may have to try several times to make a really big bubble.
—When he’s made a bubble, have him touch it gently with a wet finger to see what happens.
—Have him make another big bubble, then touch it with a dry finger. What happens?
★ Ask him to look closely at the bubbles he makes. How many colors does he see? Do the colors change?
Bubbles are bits of air or gas trapped inside a liquid ball. The surface of a bubble is very thin. Bubbles are particularly fragile when a dry object touches them. That’s because soap film tends to stick to the object, which puts a strain on the bubble.
Bugs!
Kindergarten–Grade 1
Children can improve their understanding of the natural world and their classification skills by observing bugs.
What You Need
★ Books about insects and spiders—preferably with photographs
★ A magnifying glass
What to Do
★ With your child, search your home and neighborhood for bugs.<!>
Look for bugs:
—around your front door
—in cracks in the sidewalk
—in gardens
—at picnic areas
—on lights
— in corners of rooms
★ Using the guides, help your child to identify each type of bug that you find, such as ants, spiders, beetles, crickets, bees, flies, butterflies, mosquitoes, moths, wasps or ladybugs.
★ If you find ants, point out that ants work together as a community. Have her observe, for example, what an ant does when it finds a bit of food. Explain that when an ant finds food, it doesn’t eat it on the spot. It runs back to the hill to “tell” the other ants. As it runs, it leaves a trail that the other ants can smell. These ants can then find the food by smelling their way along the trail.
★ Find out about spiders:
—Why do spiders spin webs?
—What are webs made of?
—How many pairs of legs do they have?
★ Help your child to think of other ways that she might classify the bugs— for example, by color or by size or by whether they have wings or antennae
Bugs do what they do to survive. They’re constantly looking for food. Bugs can be both helpful and harmful. Termites, for example, have a bad reputation because they destroy houses by eating the wood. But termites have a good side, too. In a forest, they break down dead trees, which keeps the forest floor from becoming too cluttered.