David L. Drotar Written by Mel Mann Illustrated by Magic Paper You Will Need: Sheet of paper Instructions: Do you know a fast way to stick a piece of paper to your hand without using any glue or tape? Would you believe that air will do the job? Well, it will! Just follow the steps below. 1. Hold your arm straight at your side. Turn your hand so that the palm faces forward. 2. Press a flat sheet of paper to your palm, using your other hand. Now start running as fast as you can and take away the helping hand. The paper will stay in place as you run. This Is What Happens: Even though you can’t see air, it is a substance, just like anything else, and it exerts a force against objects. When you ran with the paper, you created a force pushing against the air. The air pushed back against the paper and held it in place against your hand. Lighter Than Air You Will Need: String Wooden dowel Tape 2 paper lunch bags Candle Matches THE HELP OF ONE OF YOUR PARENTS Instructions: What is lighter than air? Do this experiment to find the answer. 1. Tie a piece of string to the center of a wooden dowel and attach the free end of the string to a support, such as the center of a doorway. Tape equal lengths of string to the bottom of 2 paper lunch bags and tie these upside down to the ends of the dowel. Adjust the paper bags so that they balance perfectly on the dowel. 2. Hold one of the bags in its balanced position and ask your parent to light a candle and hold it under that bag for several seconds. When the candle is taken away, let go of the bag. The bag will rise. This Is What Happens: The candle flame heats the air inside the bag. This hot air is surrounded outside by cooler air. The cooler air is heavier than the hot air and lifts the bag of hot air upwards. What is lighter than air? Air, of course! Come Glide with Me You Will Need: Sheet of typing paper Instructions: 1. Hold an 8.5 by 11-inch sheet of typing paper high above your head. Use both hands to grasp the paper. Let go. The paper will scoot in various directions and probably turn over. 2. Now make two folds in the long side of the paper, first, 1 inch inward, then, 1 inch again. 3. Hold the paper over your head as you did before, but make sure that the folded edge is at the front, and on the underside, of the sheet. Gently push the paper as you release your grip. The paper will not turn over and will glide for some distance before falling to the ground. This Is What Happens: As the plain sheet of paper falls, the force of the rushing air over it causes differences in air pressure over different parts of the paper. The front end tilts up, and the paper may move in a topsy-turvy fashion. However, by folding the edge, you increase the weight that is at the front, and this weight balances the upward force of air, causing the paper to glide smoothly without flipping over. Airplane wings are shaped like this also—they are a little bit heavier in front than they are in the rear—which helps make the ride a smooth one. All Kangaroos, Please Step Aside You Will Need: Cardboard Pencil Scissors Book Instructions: 1. Draw a V-shaped pattern like the one shown in the illustration on a piece of smooth, stiff cardboard. Cut it out, making sure the corners are rounded. 2. Hold a book in your left hand, with the binding pointing upward at an angle. Place the cardboard shape on the book so that one arm hangs off the side. 3. Hold a pencil along the side of the book. Quickly move the pencil forward and strike the cardboard so that it spins and flies off the book. In a few seconds, the cardboard will be back at your feet! This Is What Happens: You have just made a boomerang. Because of its shape, the boomerang returns to the thrower, continuing to spin in the same path without turning over. Boomerangs, used by native Australians and usually carved from wood, can be used as weapons or for hunting or just for the fun of it. Sister Twisters Yon Will Need: 2 sheets of paper Pencil Ruler Scissors Instructions: 1. With a pencil and ruler, draw two rectangles that measure 12 by 6 inches on ordinary note paper and cut them out. 2. Now, make a cut lengthwise on each piece of paper as if you were cutting them in half, but do not cut all the way through. Make each cut only 6 inches long. 3. On both pieces of paper, fold one of these flaps one way, and the other in the opposite direction. 4. On one piece, make continuous 1-inch folds along the uncut side. On the other piece, fold the uncut side into a triangle, then fold it again into another triangle. 5. Stand on a chair or bench. Drop your two creations to the ground. They will twirl and spin gracefully like two ballerina sisters. This Is What Happens: You are using the same principle to operate your spinners that helicopters use to fly. The folded end of the paper is a little heavier than the rest of the piece, and this weight keeps the end always pointing down. The rotating paper wings fall against a greater amount of air than if they did not rotate. This decreases the speed at which the device drops, keeping it aloft for a longer period of time. Tight Squeeze You Will Need: Cork Glass soda bottle Petroleum jelly Water Instructions; 1. Find a cork that will fit a glass soda bottle. Rub petroleum jelly around the sides of the cork. 2. Fill the bottle with water, about 1 inch from the top. Set the cork in the mouth of the bottle, but do not press it down. Instead, form a tight fist and slam the cork with one sudden blow. The cork will pop out. Now, press the cork in place slowly. It will stay there. This Is What Happens: Scientists say that air is elastic. When air is squeezed, it will press right back. This is what happened when you forced the cork down suddenly. The air left in the bottle was squeezed, so it pushed upward and sent the cork flying out. However, when you press the cork in slowly, the compressed air has time to leak through the seal between the cork and the glass. Heavy Air You Will Need: Basketball Air pump Scientific scale (one that shows grams or fractions of ounces) Instructions: 1. Pump up a basketball very hard. You can use a bicycle pump if you have the proper needle for inflating sports equipment. 2. Now weigh the basketball on the scientific scale. Your science classroom probably has this type of scale. Ask your teacher to show you how to use it. 3. Let all of the air out of the basketball and weigh it again. This time it weighs less. Can you explain why? This Is What Happens: Did you know that air has weight? Even though air does not weigh very much compared to the objects that we normally place on scales, you saw the slight difference between an empty basketball and one that was pumped up. This difference in weight was due to the amount of air inside the ball. There is a layer of air over the entire earth, and it, too, has weight, and exerts pressure on us. Paper Race Yon Will Need: 2 sheets of paper Chair Instructions: This experiment takes only a few seconds to perform, but you may want to repeat it a few times and think about the scientific principle before reading the explanation at the bottom of the page. 1. Use two sheets of paper that are exactly alike. Crumple one piece of paper into a ball. Do not do anything to the other piece. 2. Stand on a chair and hold one piece of paper in each hand. Extend your arms as high as possible. Drop the crumpled piece and the flat piece at the same time. Which paper falls faster? You know that they both weigh the same. Can you explain the difference in speed? This Is What Happens: Even though both pieces of paper weigh the same, they are shaped differently. The crumpled piece is more compact and is, therefore, able to push through the air better. The flat paper has more surface area and the air pushes against this and slows the paper down. Engineers who build airplanes and rockets know this scientific principle very well. They design their vehicles with a streamlined shape so that they can slice through the air instead of pushing against it. Bring on the Rings You Will Need: Oatmeal box, Scissors, Balloon, Rubber band Ammonium chloride (available in a drugstore) Aluminum foil, Tweezers, Candle THE HELP OF ONE OF YOUR PARENTS Instructions: 1. Cut a hole about the size of a half-dollar in the bottom of an empty oatmeal box. (The other end is completely open.) Slice open a large balloon so that you have a flat rubber piece. Stretch the rubber over the open end of the box and secure it with a rubber band. 2. Place quarter teaspoon of ammonium chloride into a small cup-shaped piece of aluminum foil. Hold the foil with tweezers, while one of your parents gently heats it over a candle flame. (Ammonium chloride is a harmless chemical when it is burned.) 3. Thick white smoke will begin to form. When this happens, direct the smoke into the oatmeal box through the hole you have cut. 4. Now you are ready for some stunts. Tap the center of the rubber on your oatmeal box. A beautiful smoke ring will whiz out of the hole. Try to make one smoke ring pass through the center of another one, or try to knock down a light paper figure by shooting a smoke ring toward it! This Is What Happens: You have just produced vortex rings, which is simply whirling air. The smoke that you added serves to make the rings visible to your eyes. Did you notice that the smoke rings keep their shape for a long time? This happens because the only force that breaks them apart is the movement of air outside the rings.