MANY THANKS TO NORA RADU FOR MAKING THESE
EXPERIMENTS FROM HER AFTER SCHOOL ENRICHMENT
PROGRAM AVAILABLE TO EVERYONE!
RAIN IN A BAG!
Rain in a Bag Activity
Materials needed:
· Clear, plastic, resealable baggie -- sandwich size
· White paper cut to the size of the baggie.
· Scissors
· Permanent magic markers
· Water
What you do:
1. Draw a picture that includes a lake, a tree, a sun with a smiley
face, and two clouds on the paper – make it the size of the baggy.
2. Slide the paper inside the baggy. Trace the scene onto the baggy
with permanent magic marker. It will not work with washable markers.
3. Remove the paper.
4. Fill the baggie with water to the top of the "lake" and seal it.
5. Tape the baggie to a sunny window.
As time goes by, the sun heats the water and air that is sealed in the bag.
The water evaporates until the "clouds" can't hold any more water. Then it
starts to rain.
MAKE YOUR PENNIES SPARKLE!
Materials Needed:
old, dull pennies
lemon juice
kitchen paper towels
paper cups
What to do:
1. Check with a grown-up before you begin.
2. Put a penny in a paper cup.
3. Pour some lemon juice into the cup. Make sure the penny is
completely covered.
4. After about 10 minutes, take the penny out of the lemon juice, rub
it off with a paper towel. What does the penny look like now? It should be
much brighter.
What’s happening?
A new penny is partly made from bright, shiny copper. But after a while, it
loses its shine. Why? Because the copper mixes with the oxygen in the air
and makes a coating called an oxide. When you put the penny in lemon juice,
the acid in the lemon chemically removes the oxide, and you're left with a
bright copper penny.
Try out other kinds of liquids. Will vinegar work? How about orange juice,
cola or salt water? Or vinegar and salt? Or Ketchup?
References:
1. http://pbskids.org/zoom/activities/sci/polishingpennies.html
2. http://www.exploratorium.edu/science_explorer/copper_caper.html
TURNING MILK INTO PLASTIC!
Materials Needed:
½ cup of milk or heavy cream
white vinegar or lemon juice
saucepan
strainer
kitchen paper towels
What to do:
1. Ask a grown-up to slowly warm up the milk (or heavy cream).
2. When it begins simmering, stir in a few (~4-5) spoonfuls of vinegar
or lemon juice.
3. Continue adding spoonfuls of vinegar and stirring until it begins to
gel.
4. Now let it cool for a couple of minutes.
5. Line the strainer with a couple of kitchen paper towels. Strain it
and squeeze out as much liquid as you can.
6. Put your plastic milk on a paper towel and let it dry for a few
minutes and then you can play with it. It feels like rubber. You can also
mould this into a shape. If you leave it out, it will harden.
What’s happening?
The substance you have made is called casein. Casein is the name for a group
of proteins found in milk that are also used to make cheese. Casein is mixed
with other ingredients to make a type of plastic that's used for buttons.
If you shape the casein you made into discs, you can use them for game
counters or for decorating. If you make some holes in the middle of the
discs you can use them as buttons. You can add color by rubbing food
coloring into the casein before it dries, or by painting the discs after
they're dry.
References:
1. Bennett, Andrea T.; Kessler, James H. Apples, Bubbles, and Crystals:
Your Science ABCs; American Chemical Society: 2004.
2. http://pbskids.org/zoom/activities/sci/plasticmilk.html
3. http://www.ratlab.co.uk/makeplastic.htm
4. http://www.spartechsoftware.com/reeko/Experiments/ExpMakingPlastic.htm
STEREO HANGERS!
What you need:
- a metal hanger
- two 12-inch pieces of string
What to do:
- Tie a piece of string to each corner of a coat hanger.
- Loop the string around your index fingers.
- Swing the hanger so it taps against the side of a table or chair.
What do you hear?
- Put your index fingers (with the string attached) in your ears.
- Tap the hanger again. Now what do you hear?
What happens if you replace the string with sewing thread or fishing line?
Or what happens if you hang different object from the string, like a metal
or wooden spoon?
What’s happening?
When you tap the hanger, it vibrates (moves back and forth). This makes the
air around it vibrate. When these vibrations travel into your ear, you hear
them as sound. If you listen to the hanger with your fingers in your ears,
the vibrations travel through the string and into your ears. It sounds
different because sound travels differently through string (a solid) than
through air (a gas).
Reference: http://www-
tc.pbskids.org/zoom/printables/activities/pdfs/stereohanger.pdf