# Nature's Magician.

Chances are you used it today! It's tasteless, odorless, colorless, and transparent. It can change shape, even disappear! It is so common you probably don't even think about it, but its magical properties may surprise you. What is it? Water!

Water is a combination of the gases hydrogen and oxygen. At 32 degrees F. it freezes (ice); and at 212 degrees F. it turns into a gas (steam). In between those temperatures it's liquid--which means don't spill it, or you'll have a mess!

Did you know that water has skin? This skin is called "surface tension." It is formed because water molecules (2 atoms of hydrogen + 1 atom of oxygen = 1 molecule of water) stick together. Try this to see surface tension at work:

YOU WILL NEED:

Paper towel Paper clip Water glass filled with water

DIRECTIONS:

1. Carefully float a small piece of paper towel on the surface of the water.

2. Quickly but gently place the paper clip on the towel.

3. Watch as the towel sinks but the paper clip remains on the surface.

What Happened?

The cohesion (ko-HEE-zhun) or surface tension caused by the water molecules sticking together held up the light paper clip. Try this: push one end of the paper clip into the water very slowly. Watch closely, and you can see the exact moment the clip "pops" through the surface.

Why does an ocean liner float while a quarter sinks? It's not always true that heavy things sink and light things float. The buoyancy (BOY-ansy), or how well an object floats, depends partly on how much water it displaces (pushes aside).

Any object displaces water. This displacement is what happens when you get in the bathtub and the water level rises. An object that weighs the same or less than the water it displaces will float. If it weighs more than the water it pushes aside, it sinks.

Try this:

YOU WILL NEED:

A water container at least the size of a small saucepan

Modeling clay or putty

DIRECTIONS:

1. Mold the putty or clay into a boat shape and carefully place it on the surface of the water.

2. Now roll that same piece of clay into a tight ball and put it in the water.

What It Means:

Some insects, like the water strider, can actually walk on water because their weight doesn't break through this skin of surface tension. Other water insects use the surface of the water like a ceiling, hanging upside down from it like a tiny bat.

What Happened?

The clay that was spread out into a boat shape floated, while the same clay in the shape of a ball sank. Why? The shape of an object can determine how much water it displaces, or pushes aside. If an object is broad enough to push aside enough water to equal its weight, like a boat, it will float. If the water it pushes aside doesn't weigh much as it does, like the ball. goes.

Air also improves an object's buoyancy. Items such as apples, inner tubes, and tennis balls float because they contain air. Try gathering some objects from around your house to see if they float. Observe the results. Did some of the objects surprise you? What It Means:

What It Means:

Many fish use an air-filled sac called a "swim bladder" to improve their buoyancy. But some sharks lack this sac. That means the only way they can avoid sinking to the bottom of the ocean is to swim and swim and swim without ever stopping.

The Pressure Is On

Have you ever dived to the bottom of a swimming pool and felt pressure on your ears? deeper water has greater pressure, because of the weight of the water above. Try this:

YOU WILL NEED:

A plastic soda, milk, or water bottle Adhesive tape

DIRECTIONS:

1. Poke three holes at different levels in the bottle, one high, one in the middle, and one toward the bottom.

2. Cover the holes with tape, then fill the bottle with water.

3. Quickly remove the tape.

What Happened?

The strongest stream spurted from the hole closest to the bottom of the bottle. The pressure pushed the water out that hole with the greatest force.

What It Means:

Water is heavy; try carrying a bucket of it very far and you'll see. At great depths like those found in the ocean, creatures become so accustomed to the enormous pressure of all that water above them that it's very difficult to bring them to the surface alive. The much lighter pressure usually means they simply explode.

Amazing Waters!

1. Water's solid form, ice, is lighter than its liquid form. So which is heavier, twenty pounds of ice or twenty pounds of water?

2. Water boils at 212 [degrees] F. at sea level, but at only 198 [degrees] F. 35,000 feet in the air. (The increased air pressure at sea level keeps the water from boiling until the higher temperature is reached.)

3. Water somehow manages to climb up plants, when everywhere else it runs only downhill. Otherwise if you wanted to admire a pretty flower you'd have to borrow a shovel and start digging.

4. Water is the softest of substances, but it can carve through solid rock, support the weight of a battleship and cause storms that can wipe out whole towns.

5. The earth's surface is almost all water, but most is too salty to drink--typical bad planning on the part of the earthlings.

6. Although many icebergs break off from pack ice, which is frozen seawater, they can still be melted for drinking purposes. This is because when water freezes, the salt in it is pushed out; there is no such thing as salty ice.

7. An iceberg 80 feet high and 300 feet long in 70 [degrees] F. water would melt in only 4 days.
COPYRIGHT 1999 Benjamin Franklin Literary & Medical Society, Inc.
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