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MAKE A SPLASH! THE SCIENCE OF WATER

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Splash

MAKE A SPLASH!
THE SCIENCE OF WATER

By Becky Rupp

Fill your summer with science with these fun water experiments from homeschooling’s resource guru Becky Rupp!

EXPERIMENT: EXPLODING MILK

You will need:

A bowl
Water
Milk
Food coloring
Liquid soap

What to do:

Fill the bowl about half full of water. Add a small amount of milk – just enough to make the water look white and opaque.

Dot the milky water with a few drips of different colors of food coloring. (Be careful not to shake it up.)

Now add one tiny drop of liquid soap to the center of the bowl.

Watch!

What happened?

The chemical formula for water is H2O. That means that each water molecule is made of one atom of oxygen (O) with two atoms of hydrogen (H) connected to it. If you could see a water molecule, it would look like a teddy bear’s head.

The atoms in water have an electrical charge. The oxygen atom has a negative charge and the hydrogen atoms have a positive charge. This makes water molecules all stick together. Those electrical charges attract each other. Water molecules act like a bunch of little magnets. The positive Hs stick to the negative Os of their molecular next-door neighbors.
The surface of any glass, jar, bowl, puddle, lake, river, or ocean of water is really a very thin skin of trillions and trillions of stuck-together water molecules. Scientists call this property of water surface tension. Water bugs can walk on water because of surface tension – because water molecules all link up to form a thin skin.

SOAP pulls all those linked-together water molecules apart.
That’s why all the blobs of food coloring explode outwards – they’re not held in place by the thin skin of water molecules anymore.

Try sprinkling black pepper on the surface of a bowl of water and milk. Add a drop of soap.

What do you think would happen if you dabbed some soap on a water bug?

EXPERIMENT: FLOAT A PAPER CLIP?

You will need:

A cup of water
A paper clip
Steady hands
Optional: a plastic fork

Sometimes this works best if the paper clip is a little oily – try rubbing it on your forehead before you start – and sometimes it’s a little easier if you lower your paper clip very gently onto the surface of the water with a plastic fork.

Got it to float? That’s because the surface tension of water – the way it forms that thin stuck-together skin of molecules – is strong enough to hold up a paper clip.

What will happen if you add SOAP?

EXPERIMENT: THE SOAP-POWERED SPEEDBOAT

You will need:

An index or business card
Scissors
A flat pan of water
Liquid soap

Cut the card as shown below to make your boat.

Float the boat gently on surface of the water in the flat pan.
Very carefully add a drop of soap in the notch at the back of the boat.
Warning: you can only do this ONCE. To repeat the experiment, you’ll have to empty the pan and get fresh water.

What happened?
Once you add soap to the notch at the back of your boat, the boat shoots forward.
This is because the soap breaks the surface tension and causes all the water molecules to pop apart, carrying the boat along with them.

EXPERIMENT: WHAT DISSOLVES?

You will need:

Clear plastic cups
Spoons
Water
Samples to be dissolved: salt, sugar, flour, sand, baking soda, pepper, vegetable oil, glitter, etc.

What to do:

To each cup of water, add a spoonful of sample and stir. What dissolves? (Does it make a difference if you use hot water?)

Record your results on the data sheet on the next page.

See also What Happens If You Make a Homeschooling Mistake?

DATA SHEET: What dissolves in water?

YES NO

Salt

Sugar

Flour

Sand

Baking Soda

Pepper

Oil

Glitter

What happened:

The liquid that something gets dissolved in is called the SOLVENT.

The stuff that’s added to the solvent is called the SOLUTE.

In this experiment, water is the solvent and salt, sugar, and your other samples are the solutes.

When something dissolves, the water molecules stick to it, until pretty soon the dissolving stuff is spread all through the water, completely surrounded by water molecules. That’s what happens to salt and sugar.

When something doesn’t dissolve, water molecules don’t stick to it. So it stays all clumped together and just floats around or sinks to the bottom (like sand) or floats to the top (like oil).

EXPERIMENT: COOL OOZE

You will need:

Clear plastic cups
Water
Food coloring
Vegetable oil
Shakers filled with salt

What to do:

Fill the cup with about three inches of water. Add food coloring.

When you’re happy with the color, add 1/3 cup of vegetable oil and wait until the layers settle.

(What happens? Does oil dissolve in water?)

Now carefully shake salt into the cup while you count to five.

Watch what happens. Try it again.

What happens:

Oil floats on water because it’s not as dense as water – that is, it’s lighter. Oil doesn’t dissolve in water.

Salt, however, is denser (heavier) than water, and it does dissolve in water. When you shake salt onto the oil, it sticks to the oil, weights the oil glob down, and drags it to the bottom of the cup.

But then, once the salt contacts water, it starts to dissolve. When it dissolves, it lets go of the oil, which – now that it’s no longer held down by all that heavy salt – floats right back up to the surface again.

EXPERIMENT: MOPPING UP THE MESS

An oil spill is an awful thing to happen to water. Think you can clean one up? Let’s try.

You will need:

Rectangular glass baking dish or other equivalent flat pan
Water
Salt
Blue food coloring
Plastic cup
Vegetable oil
Cocoa powder
Spoon or stirrer
Sorbents: Pieces of paper towel, cotton balls, scraps of cloth, small sponge, etc.
Small paper cups
Tweezers, tongs, or pair of plastic forks

What to do:

Fill the baking dish or pan almost to the top with water. Add blue food coloring and 1 tablespoon of salt. Mix. This is your ocean.

In the plastic cup, mix 3 tablespoons of vegetable oil with 2 tablespoons of cocoa powder. This is your crude oil.

Get the cup down close to the water and very slowly pour the oil onto the surface.

Ick. Now clean it up. See what works best get the oil out of there.

Try sopping it up with different sorbents. (Use tweezers, tongs, or forks to move the sorbents around and lift them out of the water.)

You see what a hard job it is.

Read about oil spills:

Oil Spill!
Melvin Berger; HarperCollins, 1994
This volume in the popular Let’s Read and Find Out science series covers the causes of oil spills, including the Exxon Valdez disaster, the ecological damage oil spills do, and the methods people use to clean them up. Illustrations include diagrams and maps. For ages 5-9.

EXPERIMENT: CHROMATOGRAPHY

You will need:

Coffee filters
Jar or cup
Water-soluble felt-tip markers
Drinking straws
Scotch tape
Water

What to do:
Cut a strip from the middle of the coffee filter, approximately one inch wide and four inches long.

About half an inch from one end of the strip, make a dark dot with a felt-tip marker. Choose a color that might turn out to be a mix of colors (green, brown, and black are good picks). Or try several colors on different strips

Put about a quarter of an inch of water in a glass jar or plastic cup.

Make a fold about a quarter of an inch wide at the end of the filter paper opposite the marker dot.

Tape the fold to a plastic soda straw.

Rest the straw across the top of the jar or cup such that the end of the paper with the marker dot just dips into the water. Do not submerge the dot itself.

Wait and watch. The water will be sucked up through the paper, carrying the pigments in the marker ink with it.

Once your chromatography strips are dry, tape them here:

What’s it all about?

Chemists use different kinds of CHROMATOGRAPHY to separate mixtures into their component parts – that is, to find out what’s in stuff. The word CHROMATOGRAPHY literally means “color writing.”

This is how it works:
A sample of your mixture is dotted near the end of a piece of filter paper. The filter paper is dipped in the solvent (here, water) and left there until the solvent has traveled all the way up the length of the paper. As the solvent moves up the paper, it dissolves the sample and carries the sample along with it.
The different compounds in the sample will travel up the paper at different speeds, depending on how big their molecules are. (Think of a horse race in which some of the horses are huge and slow and some are little and fast.) At the end of the experiment, you should be able to see that the different-colored compounds in your sample have separated and appear at different levels on the filter paper.

EXPERIMENT: SAVING AMELIA EARHART

Amelia Earhart (1897-1937) was a famous early aviator. She was the first woman to fly across the Atlantic Ocean. She vanished over the Pacific Ocean in 1937 while trying to fly around the world.

Some people think that Earhart and her co-pilot landed on an island and died there, possibly because they could find no fresh water to drink. There was nothing but saltwater.

How to make a SOLAR STILL:

You will need:

Water
Salt
A large bowl
An empty glass
Plastic wrap

What to do:

Add spoonfuls of salt to a container of water and stir until dissolved. Pour about two inches of the saltwater into a large bowl.

Put an empty glass (bottom down) in the center of the bowl. The top of the glass should be shorter than the top of the bowl (but higher than the saltwater).

Cover the bowl, saltwater, glass, and all with a sheet of plastic wrap. The plastic wrap should be a little loose and saggy. Tape the edges to hold the wrap tightly around the rim of the bowl.

Put a small rock or other heavy object on the plastic wrap to weight it down directly over the glass. (This will help you collect your fresh water.)

Place the bowl in the sun and wait. The longer you leave it in the sun, the more fresh water you’ll collect.

Once enough water collects in the glass, take it out and taste it. Is it still salty?

What happened:

Some people call solar stills “rain machines” because they’re really making rain.

As the salty water in the bottom of the bowl is warmed by the sun, it begins to evaporate. Now in the form of water vapor, it rises until it hits the plastic wrap. There it cools down and condenses to form water droplets. (In the sky, this happens in clouds.) The droplets then run down the plastic to a point under the rock and drip into the cup.

When the water evaporates, all the salt is left behind, so that when the water condenses it’s fresh and ready to drink.

More about Amelia Earhart:

Amelia and Eleanor Go for a Ride.
Pam Munoz Ryan; Scholastic, 1999
In the middle of a dinner party at the White House in 1933, Amelia Earhart and First Lady Eleanor Roosevelt slipped away for an airplane ride. For ages 5-9.

A Picture Book of Amelia Earhart
David A. Adler; Holiday House, 1999
A picture-book biography of Earhart for ages 5-9.

Who Was Amelia Earhart?
Kate Boehm Jerome; Grosset & Dunlap, 2002
A chatty and interesting chapter biography of Earhart for ages 9-12

EXPERIMENT: SINKING SHIPS

How safe is your boat?

What you need:

A large container of water, suitable for floating boats
Aluminum foil
Modeling clay
Pennies

What to do:

Tear the foil into (approximately) ten-inch squares.

Fold and bend foil to make a boat. See if it floats.

How many pennies can the boat hold before it sinks?

Try making a clay boat. What shape works best? How many pennies can the clay boat hold before it sinks?

More on sinking ships:

Mr. Gumpy’s Outing
John Burningham; Henry Holt and Company, 1995
Mr. Gumpy is off to go punting in his little boat, and everyone wants to go along. For ages 4-8.

Who Sank the Boat?
Pamela Allen; Putnam Juvenile, 1996
One by one, a pig, sheep, cow, and donkey, wedge themselves on board a boat – and then a last little mouse. But really – who sank the boat? For ages 4-8.

Polar the Titanic Bear
Leighton H. Coleman and Daisy Corning Stone Speddin; Little, Brown Books for Young Readers; 2001
Part non-fiction account, part fictional tale, the story of the famously sinking Titanic is told from the point of view of a stuffed bear. Illustrations include period photos. For ages 6-12.

The Titanic: Lost and Found
Judy Donnelly; Random House Books for Young Readers, 1987
A friendy and straightforward non-fiction account of the sinking of the Titanic. For ages 5-9.

EXPERIMENT: BUBBLE, BUBBLE

Soap and water is wonderful stuff because it makes BUBBLES. Can you blow a square bubble? A giant bubble?

What you need:

Bubble solution (sample recipe below)
Pipe cleaners
Quart-sized milk cartons
Paper
Masking tape
Wire coat hangers
Drinking straws
Paper cups
Yarn

Recipe for bubble solution:

6 cups water
2 cups dishwashing liquid (Joy or Dawn)
¾ cup light Karo syrup

MAKE IN ADVANCE.

For best effect, bubble solutions should sit for several hours before using.

A whole bunch of bubble blowers:

Bend pipe cleaners into shapes. Try circles, squares, triangles, zigzags, and figure eights. How about a cube?

OR cut the ends off a quart-sized milk carton – dunk one end in the bubble solution.

OR make a pipe by poking a straw into the bottom side of a paper cup. Dunk the cup upside-down into the bubble solution; then blow through the straw.

OR make a bubble-blowing tube with two sheets of paper:

Roll the two sheets into a tight cone such that the opening at the wide end is a little over an inch in diameter.

Tape with masking tape. Cut the mouth (small end of the tube) and trim the large (bubble-dipping) end of the tube such that it is even and smooth.

What about GIANT BUBBLES?

Try using a wire coat hanger. Pull the hanger out into the (approximate) shape of a circle. (For even better bubbles, wrap the wire in yarn.) Bend the hanger handle up to serve as a handle. (For safety, wrap the end of the handle in duct tape.)

OR thread yarn through two drinking straws, knotting the ends to make a bubble device of any size you like. Experiment.

How does it work?

A bubble is a thin film of soapy water, filled with air. Actually the soapy film is a lot like a sandwich: it’s really a thin layer of water with a layer of soap molecules on either side.

Did you get any square bubbles?

Well, probably not. Bubbles always try their best to become spheres. The sphere has the smallest possible surface area for a given volume – which means that it’s the most stable form a bubble can take.

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