B has practiced it several times- I think she likes to rehearse as an excuse to blow huge bubbles through the straw. In fact, she finds so much fun in the experiment, that she packed 15 straws so that each of her classmates can also blow bubbles- to really study “surface extension” as b calls it.
Learning About Surface Tension- Bubbles
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.
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?