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Questions to Ask
Why do scientists use magnification? Where have you seen things
magnified?
Tips for Less Mess: Cover the work surface and keep paper towels
within reach.
Science Connection
The speed at which light travels through water is different from
its speed in air, which makes the light bend, or refract, where
the water and air meet. The curvature of the water drop also acts
as a lens because light passing through the center has farther to
go through water than light passing through the edge. These two
effects together make the droplet act as a magnifier.
When the straw is dipped into the water, some water enters it--
reaching the same level as in the cup. Air pressure is pushing down
equally on the water in the cup and in the straw. When you close
the straw with your finger and lift it, a tiny bit of water flows
out, and the air remaining in the straw expands to take its place.
This reduces the pressure of the air in the straw. So the air pressure
pushing down on the water in the straw is less than the full pressure
of the air in the room pushing up on it. Thus the water stays in
the straw until you release your finger.
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Why
To explore some of the characteristics of water
What You Need
A small container (bottle cap) of water
Drinking straw cut in half
Clear plastic bag
Newspaper page with small letters
What to Do
Place the bag on top of the newspaper. Put the straw in the cap
of water, and then “plug” the top of the straw with
your finger. Keeping your finger securely on the top of the straw,
take it out of the water. You now have water in the straw. Why
do you think the water stays in the straw?
Touch the straw onto the plastic, creating little droplets of
water. Can you make larger ones? What shapes are the drops?
Look closely at the drops. What do you see? How does the newspaper
print look?
Vocabulary
Drop: The small quantity of liquid heavy enough to fall in a spherical
mass.
Droplet: A tiny drop
Magnify: To make something look greater in size
Refract: The bending of a beam of light when it passes from one
material to another if the speed of light is different in the
two materials.
Sphere: A round object. All points on its surface are the same
distance from the center.
Spherical: Having the shape of a sphere
Try This
You might want to place drops of water on wax paper, aluminum
foil, or tissue. What happens? How do they compare to the drops
of water on the clear plastic?
Can you read through any of these drops?
Look at the same part of the newspaper through a magnifying glass
and then through the drop of water. How are they alike? How are
they different?
Try using both to look at the colored comics.
Drag a toothpick through drops of water. What happens? Now, place
a little dishwashing detergent on the toothpick, and drag it through
the drops. What happens? Why?
What other liquids would you like to try?
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