~A Book of Experiments~

Transcription

1 ~A Book of Experiments~ Volume II For use in teaching elementary School science Organized to support the Massachusetts Science and Technology/Engineering Curriculum Frameworks Compiled by Grade 11 Scientific and Technical Writing Students at the Massachusetts Academy of Math and Science at WPI Fall 2010

2 Table of Contents Massachusetts Science and Technology/Engineering Curriculum Framework: Physical Sciences Learning Standards--Grades 3-5 Differentiation between properties of objects (e.g. size, shape, and weight) and properties of materials (e.g. color, texture, hardness): Paper Chromatography Black Rainbow Compare and contrast solids, liquids, and gases based on the basic properties of these states of matter: Collapsing Cans Dancing Raisins Raisin the Roof Floating Raisins Harney Bouncing Raisins Egg Suction Egg in a Bottle Moving Pepper The Power of Pressure Moving Drop Dropping Pennies Sugar Volcano Sinking Sodas Three Layer Float Flubber Rubber Egg Tie Dye Milk Suspended Egg Slime! Homemade Balloon Pump Match Stick Speedboats Quicksand

3 Identify the basic forms of energy (light, sound, heat, electrical, and magnetic). Recognize that energy is the ability to cause motion or create change: Anti-gravity Water Can You Separate Salt and Pepper? Excited Salt Secret Bells A Ruler Attracts Water Disappearing Colors Give examples of how energy can be transferred from one form to another: Super Bouncy Tennis Balls A Simple DC Motor Good Conductors Mini Hovercraft Identify and classify objects and materials that conduct electricity and objects and materials that are insulators of electricity: Making a Series Circuit Lemon Light Make Your Own Flashlight Recognize that magnets have poles that repel and attract each other: Create a Compass Recognize that light travels in a straight line until it strikes an object or travels from one medium to another, and that light can be reflected, refracted, and absorbed: Magnifying Lens Focus Miscellaneous Science and Math Activities: Growing Sugar Crystals Crystalling Sugar Tension Bridge Magic Pop Cans Floating Ping Pong Balls Kite Aerodynamic The Lincoln High Dive Impulse

4 Paper Chromatography Materials Water 15 identical strips of paper Ruler Pencils Three different types of markers (including one permanent marker) A wide-mouth jar for the solvent Procedure 1. Cut paper strips about two by ten centimeters in area (they must all be the same size). 2. Take one of the paper strips and use a ruler and pencil to draw a line across it horizontally two cm from the bottom. This is the origin line. 3. Pour a small amount of water into your jar (there should be barely enough for the paper strip to hang inside of the jar and just touch the water). 4. Using one of the markers, place a small dot of ink onto the line.

5 5. Use the pencil to label the strip, so that you know which marker it represents. 6. Tape the paper to a pencil and hang it into the jar of solvent so that the bottom edge is just barely touching. 7. Let the water rise up the strip until it is almost at the top. 8. Remove the strip from the jar and mark how far the solvent rose with a pencil. 9. Analyze the ink component(s): Measure the distance the solvent and each ink component traveled from the starting position, then calculate the R f value for each component (some of the ink components might not have moved at all). 10. Repeat this experiment for each marker five times. The Scientific Explanation Water is the mobile phase of the chromatography system, whereas the paper is the stationary phase. These two phases are the basic principles of chromatography. The adhesion force is larger than the cohesion force, hence the water moves up the paper. The ink was attracted to the paper and to the water differently, and thus the various components moved to different distance depending upon the strength of their attraction. To measure how far each component traveled, the retention factor (R f value) of the sample was calculated. The R f value is the ratio between how far the component travels and the distance the solvent travels from the origin.

6 Black Rainbow Materials coffee filters washable black marker (may use more colors) beaker of water easily washable surface Procedure 1. Fold a coffee filter in half and then fold it in half again so that it takes the shape of a cone. 2. With the black marker, color in the tip of the cone. 3. Dip the colored region in the water, and then place it on the surface. 4. Wait and observe. What happens? One step further: Experiment with different colors, make different patterns, and fold the coffee filter into different shapes. What happens?

7 The Scientific Explanation Black pigments absorb every wavelength of light and thus reflect no colors. The ink in a black marker is made up of various pigments, each of which absorb specific wavelengths and reflect others. When these different particles are combined, any color reflected by one pigment is absorbed by another; therefore, the black reflects nothing. When water is added to the black marker on the coffee filter, the water spreads outward, taking with it the various colored particles from the marker clusters. The lighter pigments are then carried farther than others, leaving behind a trail of colors.

8 Collapsing Cans Materials 1 empty regular soda can 1 hot plate 1 pair of standard metal or plastic tongs 1 bowl or pot Ice (about 200mL) Water (about 800mL) Procedure Fill the can with a small amount (15-30mL) of water. Place the can on a hot plate. Heat the can until the water begins to boil and steam begins to rise. Fill the pot or bowl with the remaining water and the ice and wait for at least 30 seconds. Use the tongs to take the can off of the hot plate, flip it upside down, and place it 1-2cm into the water so just the opening of the can is covered as quickly as possible. What happened to the can?

9 The Scientific Explanation The air around us is always exerting pressure upon everything. If there is a large difference between the pressure on the outside of a closed container and the pressure within, the container can no longer support itself and it distorts. When the water was heated, water vapor formed and pushed the air outside of the can. Then, when the can was put into the cold water, the vapor in the can condensed. Very little air was left in the can so the pressure inside was far less than the outside pressure, and the outside air pressure crushed the can.

10 Dancing Raisins Materials Two clear cups (same size) Soda (preferably colorless) Twelve raisins Baking soda (1 teaspoon) Water (1/2 cup) Vinegar (1/4 cup) Procedure 1. Fill one cup three quarters of the way with soda. 2. Drop six raisins into the same cup. 3. Fill the other cup half way with water. 4. Mix in a teaspoon of baking soda with the water until it dissolves. 5. Pour vinegar into the same cup until it is filled three quarters of the way to the top. 6. Drop six raisins into that cup. 7. Watch as the raisins sink and float in both cups for the next hour. 8. Try using other objects such as moth balls or uncooked pasta to see if the experiment yields new results.

11 The Scientific Explanation Carbon dioxide is in the soda, and it is produced by the mixture of baking soda, vinegar, and water. The carbon dioxide is the gas that causes the fizzing when a soda bottle is initially opened. The bubbles formed from carbon dioxide are attached to the rough, wrinkly skin of the raisins and cause them to become more buoyant and float. The raisins sink to the bottom of the cups because they are denser than the liquid in the cup. Once the raisins float up again and reach the top of the surface, the carbon dioxide bubbles will pop and make the raisins lose buoyancy and sink again. Eventually the raisins will stay at the bottom when all of the carbon dioxide escapes into the air or when the raisins become too soggy, which makes them too heavy to be able to float to the top.

12 Raisin the Roof Materials 1 tall clear glass 5 raisins ½ cup water 1 tbsp baking soda 3/8 cup vinegar Procedure 1. Place 5 raisins in the bottom of the clear glass 2. Pour the ½ cup of water into the glass 3. Stir in 1 tbsp of baking soda 4. Slowly pour the red wine vinegar into the glass 5. Watch the raisins and record your observations

13 The Scientific Explanation A chemical reaction occurs between the baking soda and vinegar, releasing tiny bubbles of carbon dioxide. These bubbles are attracted to the rough surface of the raisins and make the raisins rise to the surface of the water. However, the density of the raisins is greater than the density of the water, so they begin to sink. Then the carbon dioxide bubbles push the raisins to the surface again, causing them to dance in a repetitive rising and sinking motion until all of the carbon dioxide has been released.

14 Floating Raisins Materials plastic container (about 4 cup size) vinegar (½ cup) water (3 ½ cups) baking soda (1 tablespoon) raisins (2 to 3) Procedure 1. Fill the plastic container with the ½ cup of vinegar. 2. Add the 3 ½ cups of water. 3. Stir the water and vinegar together. 4. Add the tablespoon of baking soda. 5. Stir the baking soda, vinegar, and water together. 6. Drop the raisins in and wait a few seconds. 7. Observe what happens.

15 The Scientific Explanation When the baking soda and vinegar are combined, a chemical reaction occurs that releases bubbles of carbon dioxide. These carbon dioxide bubbles are lighter than the water so they rise to the top of the container. When the raisins are placed into the mixture, the carbon dioxide bubbles attach themselves to the raisins and cause them to rise. When the raisins reach the surface of the water, the carbon dioxide escapes from the liquid, and the raisin sinks back to the bottom until enough more bubbles cause it to float again.

16 Bouncing Raisins Materials An unopened bottle of Sprite (16.9 ounces or 2 Liter) A box of raisins Clear plastic or glass cup Procedure 1. Place the materials on a flat surface. 2. Open the bottle of Sprite, and pour it into the clear cup about ¾ of the way. 3. Place 5-7 raisins in the cup. 4. What is happening to the raisins after a few minutes in the soda?

17 The Scientific Explanation The carbon dioxide gas bubbles released from the Sprite soda attaches to the rough sides of the raisins. The bubbles decrease a raisin s density, thus the buoyancy of the raisins will increase. The more buoyancy an object has, the more able it is to float. The gas bubbles float the raisins to the top of the soda. Then the carbon dioxide bubbles are released into the air, and the raisins float back down to the bottom of the cup. The process keeps repeating itself.

18 Egg Suction Materials 1 hardboiled egg 1 glass bottle or jar with an opening smaller than the egg Wooden kitchen matches Procedure 1. Peel the shell off the egg. 2. Place the egg on top of the bottle opening. Notice how the egg does not fall in. 3. Take the egg back off the bottle. 4. Light a match, drop it into the bottle, and quickly cover the bottle with the egg again. 5. What happens to the egg?

19 The Scientific Explanation At the beginning of the experiment, the air pressure is the same both inside and outside of the bottle. The fire inside the bottle) heats the air molecules inside the bottle, which makes them expand. Some of the air molecules escape before egg is placed on the opening. When placed on the opening, the egg seals the top of the bottle, cutting off the supply of oxygen. This extinguishes the flame, and the air on the inside of the bottle cools down. There are fewer collisions of the air molecules, which decreases the air pressure inside the container. But he air pressure remains the same on the outside of the bottle, which causes the outside air pressure to push the egg through into the bottle.

20 Egg in a Bottle Materials Boiled Egg Paper towel Matches Erlenmeyer flask or glass bottle Procedure 1. Shell the hardboiled egg 2. Shred the paper towel 3. Stick the shredded paper towel inside the flask/ bottle 4. Light the match 5. Drop the match into the flask so the paper towel catches on fire 6. Put the egg on the rim/opening of the flask so that it is sealing off the air flow 7. Watch as the egg is sucked into the flask

21 The Scientific Explanation At the beginning of the experiment, the air pressure is the same both inside and outside of the bottle. The fire inside the bottle) heats the air molecules inside the bottle, which makes them expand. Some of the air molecules escape before egg is placed on the opening. When placed on the opening, the egg seals the top of the bottle, cutting off the supply of oxygen. This extinguishes the flame, and the air on the inside of the bottle cools down. There are fewer collisions of the air molecules, which decreases the air pressure inside the container. But he air pressure remains the same on the outside of the bottle, which causes the outside air pressure to push the egg through into the bottle.

22 Moving Pepper Materials 1 clear plastic bowl 1 ruler Pepper (in shaker or grinder) 500 ml of water Liquid dish soap Procedure 1. Pour 500 ml of water into the plastic bowl 2. Put 3 shakes of pepper into the water 10cm above the surface 3. Put one drop of liquid soap into the center of the water 4. What happens after adding the soap? Record your observations.

23 The Scientific Explanation Water molecules are highly attracted to one another and stick to each other like magnets. This results in surface tension, meaning that the water molecules on top of the liquid form a skin-like layer. The reason for the movement of pepper to the outer edge of the bowl is due to the spread of the soap along the top of the water. The pepper will only remain afloat where there is no soap and surface tension remains. Pepper is pushed to the edge where it eventually sinks because of the lack of surface tension.

24 The Power of Pressure Materials Mug Manila Folder 5 Gallon Bucket Water Scissors Procedure 1. Fill the bucket with water. 2. Place the bucket on a flat surface that can get wet without any trouble. 3. Cut a manila folder into quarters, once on the seam, then widthwise on the remaining pieces. 4. Dip the mug into the bucket and fill it halfway with water. 5. Place piece of manila folder over the mug rim making sure none of the opening is exposed. 6. Keep constant pressure on the folder piece and flip the mug upside down over the bucket. 7. Observe what the manila folder does. 8. Repeat for filling the mug quarter-way, three quarters-way, and completely filled with water.

25 The Scientific Explanation We are surrounded by air, which consists of various gases. Air exerts a pressure on every single thing. On earth, air pressure is 14.7 psi (pounds per square inch). We can't feel this pressure because it is everywhere. This experiment shows the presence of air pressure using water. The water remains inside the glass, holding the manila folder piece in place. This happens because the air pressure outside, i.e., 14.7 psi, is greater than the combining pressure of the water and air inside the glass.

26 Moving Drop Materials 1-foot sheet of wax paper Toothpick Eyedropper Water Liquid dish soap Procedure 1. Spread the wax paper on a table 2. Use the eyedropper to position 3 or 4 separate small drops of water on the paper. 3. Wet the toothpick with water. 4. Bring the tip of the wet pick near, but not touching, one of the water drops. 5. Observe what happens to the water drop. 6. Repeat with one of the other drops 7. Repeat with the other two drops, but touch the tip of the toothpick to the soap before touching the water drops.

27 The Scientific Explanation Water molecules have an attraction to each other. This attractive force is strong enough to cause the water drop to move toward the water on the toothpick. The attraction of the water molecules exists because each water molecule has a slightly positive side and a slightly negative side. The positive area of one molecule attracts the negative part of another molecule. The soap on the other hand has molecules with two distinct ends. One half is attracted to water particles and the other half repels water. These soap particles break the strong forces that hold water molecules together, thereby allowing the water to spread out.

28 Dropping Pennies Materials A cup with a mouth 9 cm wide Water (enough to fill the cup completely) Several (30 +) pennies Procedure 1. Fill the cup with water until the water level is even with the top of the cup. 2. Slowly drop a penny into the cup of water. 3. Observe what happens to the water level. 4. Continue dropping pennies slowly into the cup until the water overflows down the side. 5. Record how many pennies are in the cup when the water overflows.

29 The Scientific Explanation A molecule of water is composed of three atoms: two hydrogen atoms and one oxygen atom. Because the oxygen atom tends to have the electrons orbit it more than the hydrogen atoms, the oxygen atom has a slight negative charge, and the hydrogen atoms have a slight positive charge. Because of this property, oxygen is called a polar molecule. This property also allows the water molecules to form hydrogen bonds with each other, between the positive hydrogen atoms and negative oxygen atoms. Because the individual water molecules form these hydrogen bonds, water has a very high surface tension. This high surface tension actually allows the water level to rise up over the mouth of the cup before the water overflows down the sides.

30 Sugar Volcano Materials 1 plastic cup (16 fl. oz.) 1 Styrofoam plate 1 can of seltzer water or another carbonated beverage (12 fl. oz.) 1 tsp of sugar Procedure 1. Place the plastic cup on the Styrofoam plate. 2. Pour the seltzer water into the plastic cup. 3. Take the sugar and dump it into the seltzer. 4. What happens?

31 The Scientific Explanation The seltzer will overflow the plastic cup because of nucleation sites. When the seltzer is sitting in a container, the fizz, or carbon dioxide, is trying to escape. The sugar crystals have imperfections, called nucleation sites, on their surfaces that look like dimples on a golf ball or like craters on the surface of the moon. When the sugar is dropped into the seltzer, the carbon dioxide, looking for a way to escape the liquid, grabs onto these holes. Eventually, the carbon dioxide builds up to a point in which it floats up to the surface and is seen as fizz. The reaction becomes stronger until either all the sugar is dissolved into the seltzer or all the gas has left the liquid.

32 Sinking Sodas Materials 1 can of Coca-cola 1 can of Diet Coke Cans of other assorted diet and regular sodas Plastic cooler or container (about 6 liter size) Water (about 5 ½ liters) Procedure 1. Fill the plastic cooler or container with 5.5 liters of water. 2. Place the can of Coca-cola in the container. DO NOT OPEN ANY OF THE CANS DURING THE EXPERIMENT. 3. What happens? Does it sink or float? 4. Remove the can from the container, and look at the nutritional facts on the side of the can. How many grams of sugar are there in the can? 5. Place the can of Diet Coke in the container. 6. What happens this time? Does it sink or float? 7. Remove this can from the container and look at the nutritional facts on the side of the Diet Coke can. How many grams of sugar are in this can? 8. Repeat the process for any other cans of soda you want, but Diet Coke and Coca-cola should be enough.

33 The Scientific Explanation This experiment is a demonstration of the scientific principles of density. The can of regular Coca-cola should sink because the sugar content in the can causes the soda to be denser than water. The Diet Coke should float because there is no sugar in diet soda. The cans of soda should not be opened when placed in container because the water will displace the sugar.

34 Three Layer Float Materials Cup of water Cup of vegetable oil Cup of honey A penny A grape A cork Tall drinking glass Procedure 1. Take a plastic cup and fill it to the top with water. 2. Take the second plastic cup and fill it with vegetable oil. 3. Take the third cup and fill it with honey. 4. Pour out the honey into the tall drinking glass. Do the same for the vegetable oil. Notice what happens as that is done. Repeat the step one more time for the cup of water. 5. Allow the liquids to settle for a few minutes and then drop the penny, the grape, and the cork into the glass. 6. What do you observe happening as you drop each item into the glass?

35 The Scientific Explanation Density is a measure of how tightly packed the atoms or molecules of a substance are. Density determines if an object floats or sinks when placed in another liquid. If the object has a higher density then the liquid, it will sink, and if the object has a lower density, it will float. The three liquids in the glass arrange themselves by their density. The densest liquid will sink to the bottom of the glass, and the least dense liquid rests above the denser liquids. When the items are dropped into the glass, they sink through any layers that are less dense then the items, but the items float above any layers that are denser. The penny is denser than all three liquids so it falls to the very bottom. The grape is less dense then honey so it floats above it, but it is denser than water and oil so it sinks below the oil and water. Finally, the cork floats above the oil because it is less dense then the oil.

36 Flubber Materials 4 teaspoons of sodium borate ¼ teaspoons of food coloring 2 1/3 cups of water 2 cups of glue 3 wooden mixing bowls 1 wooden mixing spoon 1 Microwave

37 Procedure Pour 1 1/3 cups of water into the first mixing bowl. Heat the water in a microwave on the high setting for 35 seconds. Pour 2 cups of glue into the first mixing bowl. Mix the solution for 60 seconds with the wooden spoon. Pour.25 teaspoons of food coloring into the first mixing bowl. Mix the solution for 60 seconds. Pour 1 ½ cups of water into the second mixing bowl. Pour 4 teaspoons of sodium borate into the second mixing bowl Mix the second mixing bowl for 60 seconds. Pour the solution from the second mixing bowl into the first. Mix the solution for 60 seconds. Pour excess fluid into the third mixing bowl. Explore the properties of the substance left in the first mixing bowl. The Scientific Explanation A polymer is a large molecule made of repeating subunits. The substance in this experiment is a silicon polymer made of sodium borate, water, and white glue. It acts as a solid and a liquid under different circumstances. Scientists call it a Maxwell solid, which means it has properties of both elasticity and viscosity. When under low stress, it acts as a Non-Newtonian fluid, which means it has a viscosity without a direct relation to its shear stress.

38 Rubber Egg Materials 1 egg 1 plastic cup Vinegar Procedure 1. Put the egg inside the cup. 2. Pour vinegar into the cup until the egg is covered. 3. Put the cup aside in a safe place and wait 3 days, making sure the egg is always covered by vinegar. 4. After 3 days, carefully take the egg out of the cup. What does it look like now? What does it feel like?

39 The Scientific Explanation What makes an eggshell rigid is the element calcium in the form of the compound calcium carbonate. When you pour on vinegar (acetic acid), it reacts with the calcium carbonate in the shell, leeching most of the calcium out into the liquid. This reaction is the reason for the flexibility of the egg after a few days; the shell dissolves, leaving behind just the membrane. Another effect of the reaction is the production of carbon dioxide, which makes all the tiny bubbles around the egg.

40 Tie Dye Milk Materials 2 cups of milk (half-and-half or whole milk work best) A shallow dish Liquid dish soap Food coloring (4 different colors) A Q-tip or toothpick Procedure 1. Pour a half of a cup of milk into a shallow dish. 2. Pour roughly six drops of each type of food coloring in the center of the dish. Each color should make a different circle. Make sure that the circles are not touching. You can do this by placing the drops in a square formation. 3. Dip the end of a Q-tip in some liquid dish soap. 4. Place the dish soap end of the Q-tip into the center of the milk. 5. What do you observe?

41 The Scientific Explanation When the food coloring is dropped onto the milk, it does not sink or spread out. This is because the food coloring is less dense than the milk. Because of this, it can just float on top, and the food coloring and milk do mix together. When the soap is added, a reaction takes place. The soap helps to break the surface tension of the water in milk by breaking apart fat molecules. This is why it is best to use whole milk rather than skim milk. The milk that has not been touched by the soap has a higher surface tension than the milk that touches the soap. Because of this, it is able to pull the surface away from the soap. This is why it looks as though the color travels away from the soap. The food coloring moves with the milk creating a tie dye effect.

42 Suspended Egg Materials A tall glass A raw egg Tap water Table salt (at least 10 table spoons) A plastic stirrer A teaspoon Procedure 1. Fill glass about halfway with tap water. 2. Add salt and using the plastic stirrer mix it with the water! 3. Find how many tablespoons it takes for the egg to float. 4. Add fresh tap water into the glass carefully; make sure the salt and fresh water do not mix. 5. Place the egg in the glass 6. What happens to the egg?

43 The Scientific Explanation Why does the egg float in salt water but sink in fresh water? This happens because of density, which defines how much mass an object for a given volume. Density is expressed by the equation: Density = Mass/Volume. The denser an object is the more compact its molecules are. Salt water is denser than fresh water, which is why the salt water sinks to the bottom. But because the egg has a density between salt and fresh water the egg floats in between the two liquids.

44 Slime! Materials 1 Teaspoon Borax 1 ½ cups water ½ cup of Elmer s glue Food coloring (optional) Measuring Cup Medium size bowl A spoon Small plastic bag Procedure 1. Pour ½ cup water into the measuring cup and 1 cup of water into the medium size bowl. 2. Add the teaspoon of Borax to the medium bowl and stir. 3. Add the ½ cup of Elmer s glue to the small bowl and stir it. It probably won t dilute completely, but most of it should be diluted. 4. Add 1-3 drops of food coloring to the glue and water. You can add more depending on the color you would like it to be (more drops = brighter slime!) 5. Empty the glue and water mixture into the larger bowl with the borax and water. What happens? 6. Use your hands to mix the slime! What does it feel like? 7. Pick up all the slime that you can from the bowl and start squeezing it (over the bowl!) to get rid of any extra water that is left in it. The more you play with it, the firmer it becomes! 8. You can store the slime in a plastic bag.

45 The Scientific Explanation The slime that you just made is a material called a polymer, which is a long chain of molecules that are connected to each other. Borax links the glue molecules to each other. As more molecules become linked together, the more putty-like the slime becomes.

46 Homemade Balloon Pump Materials Empty plastic water bottle Party balloon Vinegar (about 1.5 cups) Baking Soda (3 teaspoons) Plain piece of paper Procedure 1. Remove the cap of the water bottle. 2. Fill the water bottle with the vinegar. 3. Twist the paper into a funnel shape. 4. Use the paper funnel to pour the baking soda into the balloon. 5. Without letting the baking soda fall from the balloon, stretch the opening of the balloon over the top of the water bottle. 6. Hold the balloon down to the water bottle firmly. 7. Tilt the balloon so the baking soda falls into the water bottle with the vinegar. 8. Watch what happens to the balloon!

47 The Scientific Explanation When the vinegar mixes with the baking soda, a chemical reaction occurs. In this case, vinegar (CH 3 COOH) combines with baking soda (NaHCO 3 ) to make carbon dioxide (CO 2 ), water (H 2 O), and sodium acetate (CH 3 COONa). The carbon dioxide is a gas that is created by the mixture of vinegar and baking soda, which fills up the balloon in this experiment.

48 Matchstick Speedboats Materials 3 matches A large container full of water Dish washing liquid (one teaspoon) Procedure 1. Place the container of water on a level surface. 2. Place the three matches on the surface of the water. 3. Pour a teaspoon of dish washing liquid into the water next to one of the matches. 4. What happens to the matches?

49 The Scientific Explanation The matches float because of surface tension, the attraction of water molecules that forms a skin on the surface of liquid water. Dish washing liquid is a surfactant, which means it lowers the surface tension of the water. As the soap molecules spread, across the water, the the matches are pushed outward, and the surface tension of the water decreases.

50 Quicksand Materials One (16 oz.) box of cornstarch Plastic mixing bowl Water (1 ½ to 2 cups) Spoon Procedure 1. In the mixing bowl, combine small amounts of cornstarch and water until it has a honey-like consistency. The ratio is 1 ¼ cups of cornstarch to 1 cup of water, so for a 16 oz box use approximately 1 ½ to 2 cups of water. 2. Try gently touching the mixture and then try punching it. What does it feel like? (If the mixture splatters when you punch it, add cornstarch.) 3. Put your hand in the mixture and try to remove. Does it help if you pull your hand out slowly? 4. The cornstarch-water mixture must be disposed of in the trash not the sink.

51 The Scientific Explanation The water-cornstarch mixture is a unique substance called a non- Newtonian liquid. Viscosity is a liquid s resistance to flow, and the viscosities of non-newtonian liquids are affected by the force applied to it. Other viscosities, in more familiar liquids, are affected by pressure and temperature. This is why when a high pressure force, such as punching, was applied to the cornstarch-water mixture it felt solid.

52 Anti-Gravity Water Materials A graduated cylinder (250mL) Water Procedure 1. Measure 100mL of water using the graduated cylinder. 2. Hold the graduated cylinder by its top, keeping your arm fully extended downward. 3. Quickly move your arm in a circular motion so that the cylinder is in your hand right side up when you start, then upside-down, then right side up again when you finish.

53 4. Observe what happened. Did the water fall out of the cylinder? (if it did, try spinning the cylinder faster) 5. Repeat this process for 150mL, 200mL, and 250mL of water. Are the results the same? When do they change? The Scientific Explanation When you spin the cylinder, you exert a force on it. This means that there is something pushing on the cylinder. This force points toward the bottom of the cylinder, so the water is pushed against the bottom. The faster you spin it, the greater the force. This means that the faster you spin the cylinder, the more force is pushing on the water to keep it from falling out. If you spin the cylinder fast enough, the push on the water to stay in is greater than the pull of gravity. This force is what keeps the water in the cylinder when you spin it.

54 Can You Separate Salt and Pepper? Materials Comb Salt Pepper Wool (or hair) Procedure 1. Pour or shake some salt onto a flat surface 2. Pour or shake some pepper on top of the salt 3. Use your finger to stir the salt and pepper together until they are mixed evenly 4. Rub the comb through the wool (or your hair) in order to give it a static charge 5. Take the charged comb and slowly lower it, teeth side down, to about 2.5 cm above the salt and pepper mixture 6. Observe what happens to the pepper and salt. The pepper should jump up and stick to the comb, while the salt stays put

55 The Scientific Explanation Rubbing the comb against the wool or through your hair gives it a negative charge, like any plastic object that is rubbed against cloth or fur. The salt and pepper both have positive charges, and because opposite charges attract, they will try to move toward the comb because of the force of static electricity. When the comb is lowered above the mixture, the pepper particles fly up to the comb because of this attraction. Because the pepper particles are much lighter than the salt, they are attracted to the comb more easily than the salt, without the comb having to be lowered as close to them. This causes the pepper to separate from the salt and stick to the comb. If you move the comb closer to the salt and pepper mixture, the salt will eventually fly up and stick to the comb as well as the pepper.

56 Excited Salt Materials A latex balloon Salt (about ¼ teaspoon) A volunteer with long hair Procedure 1. Blow up the balloon and tie it at the end. 2. Put the salt on a table or other flat surface and spread it out. 3. Rub the balloon in the volunteer s hair for about 20 seconds. Make sure the balloon doesn t touch anything except the person s hand that is holding it. 4. Move the balloon over the salt, keeping it just above the table or surface. 5. What happens to the salt?

57 The Scientific Explanation When the positive side of a magnet is brought close to the negative side of another magnet, they attract each other. When the positive side of a magnet is brought close to the positive side of another magnet, they repel each other. The same thing happens when two negative sides are brought together. Salt is a charged molecule that can act like a magnet. When you rubbed the balloon in the volunteer s hair, you gave the balloon a negative charge. This negative charge acted like the negative end of a magnet and attracted the positive side of the salt, making it jump and stick to the balloon.

58 Secret Bells Materials String Scissors Wire hanger Metal Spoon Procedure 1. Cut approximately 3 feet piece of string with scissors 2. Fold the string in half 3. Put the loop under the hanger hook 4. Pass the loose ends into the loop, securing the hanger to the string 5. Grab one end of the string with each hand 6. Swing the hanger against a solid surface 7. Now put the string ends in your ears and swing the hanger again 8. Repeat the same process with a metal spoon

59 The Scientific Explanation Sound travels differently depending on the medium. It sounds different when it travels through air compared to when it travels through something solid. Sound is actually caused by molecules vibrating and bumping into each other. A chain reaction of colliding molecules occurs. This repeats until the vibrations reach your ears, where your ear drums push on the bones in your ear, and the vibrations are translated into electrical signals. When you put the string into your ears, you hear the vibrations through the string, and because the molecules of the string are different from the molecules in air, the vibrations can sound like church bells.

60 A Ruler Attracts Water Materials 2 plastic rulers 1 clean sock Paper towel a sink Procedure 1. Place one ruler in the sink. 2. Open the tap slightly, just until there is no visible dripping in the water flow. 3. Measure the distance of the water flow from the wall of the sink using the ruler. 4. Hold the other ruler in your hand at one end. 5. Clean the uncovered surface of the ruler using the paper towel. Make sure that it is dry and that there is no visible dirt on it. 6. Rub the sock on the clean surface up and down for about 30 seconds. 7. Approach the water flow with the surface. 8. Measure the maximum displacement of the water flow.

61 The Scientific Explanation By rubbing the sock on the ruler, the ruler becomes charged. There are positive and negative charges, which attract each other; however, two positive or two negative charges will repel each other. When the charged ruler is close to the water, the charges that are opposite to the charge of the ruler move closer to the ruler, and the others move away from it. Therefore the force between the water and the ruler will make the water flow move closer to the ruler.

62 Disappearing Colors Materials 1 sheet of printer paper 4 markers (red, blue, green, yellow) 1 pair of scissors 1 pencil 45 cm of string Procedure 1. Gather all materials 2. Cut out an 8.5 x 8.5 in. square from the printer paper 3. Fold all corners of the square towards its center to form a smaller, new square 4. Repeat step 3 three times 5. Tape the flaps down near each corner 6. Using the pencil, divide the side without flaps into 4 equal triangles by connecting opposite corners 7. Color each triangle red, blue, green, or yellow using the markers 8. Using the pencil pierce a hole in the center of the square 9. Put the string through the hole in the square 10. Rotate the square by spinning the string 11. Once it has gained enough speed, pull the string taut 12. Observe what happens to the colors on the square

63 Direction of Fold Flaps Finished Product The Scientific Explanation Visible light is made up of many different colors, including red, blue, green, and yellow. These colors can be separated from visible light using a prism. This experiment just does the opposite. It combines these colors to form white, which is why the colored square appears to be white when it is spinning at sufficient speeds. At these speeds our eyes cannot see each color separately, so we only see the combined effect of these colors. This effect can be enhanced by adding a wider array of colors.

64 Super Bouncy Tennis Balls Materials Basketball Tennis Ball Procedure 1. Hold the basketball and the tennis ball next to each other at about shoulder height. 2. Drop both balls at the same time. 3. Notice how high each ball bounces. 4. Hold the tennis ball on top of the basketball at shoulder height. 5. Drop both balls at the same time. 6. Notice how high each ball bounces.

65 The Scientific Explanation The tennis ball bounces very high because of momentum, the mass of a system multiplied by the velocity of a system. Momentum in a system is always conserved, so the mass and velocity are inversely proportional. In other words, as the mass decreases, the velocity increases while the momentum stays the same. In this case, the tennis ball and basketball form a system. When the two balls are dropped on top of each other, the mass of the system is the combined mass of both of the balls. When the balls hit the floor, only the tennis ball bounces up. The mass of the system decreases to only that of the tennis ball, so velocity increases.

66 A Simple DC Motor Materials Different-sized brand-new batteries (AA, AAA, C, D) Different-sized flathead screws (about 1-2 long) Assorted circular magnets (slightly larger than the head of the screws and between 1/16-1/4 thick) Some wire Wire strippers Some tape Procedure 1. Choose a battery, a screw, and a magnet to use for the experiment. Hint: Smaller batteries, longer screws, and medium magnets seem to work well. 2. Cut a piece of wire to about nine inches long and strip ½ on each side. 3. Tape one side of the wire to the negative side of the battery. Make sure that it makes contact and is strong. 4. Place the magnet on the center of the head of the screw, and try to balance it. 5. Place the tip of the screw on the center of the positive side of the battery. It will stick due to the power of the magnet. Make sure to hold the battery so that the battery with the screw on it faces straight down.

67 6. Lightly touch the end of the wire that isn t attached to the magnet. It will take a few trials, but the screw should begin to spin. You have now created a motor! Students should try different sizes of batteries, screws, and magnets, and try to find the best combination to allow the motor to spin the best. Safety note: This experiment does involve electricity, which can be dangerous if handled incorrectly. Creating a motor makes a short circuit, where the positive and negative terminals of a battery are connected directly. Do not leave the motors connected for more than a few seconds, and give the battery time to rest between trials. There are also sharp objects involved, and these should be handled with care. This experiment should always be conducted under adult supervision. The Scientific Explanation The motor made here is often known as a homopolar motor. This special type of motor rotates due to the current passing through the battery, wire, and magnet. The magnet turns the battery into a single pole of a magnet, which allows the Lorentz Force to come into play. The Lorentz force means that a charge moving in a uniform magnetic field (the battery casing) experiences a force perpendicular to both the field and the direction of the current flow. This force causes the wire to repel the screw, and this causes the rotational motion of the screw. Although it doesn t look like a standard motor, it uses the same essential principles.

68 Good Conductors Materials One Pyrex brand 750 ml glass bowl 500 ml of water Thermometer 15mm wooden popsicle stick 16mm stainless steel spoon 16mm plastic spoon ½ stick of Great Value Price Chopper brand butter 1 bag of M&M s 1. Fill the glass bowl filled with 500 ml of hot water. 2. Take a temperature reading of the water. 3. Place one Popsicle stick, one metal spoon, and one plastic spoon vertically in the water, leaning each against the edge of the bowl. 4. Put 0.15g of butter at the end of the out-of-water part of each object. 5. Stick on M&M to the buttered end of each object, using the butter as an adhesive. 6. After 5 minutes, take another temperature reading of the water. 7. The first object that s candy falls off is the best conductor of heat out of the three objects.

69 The Scientific Explanation The heat from the water travels up the metal spoon, plastic spoon, and popsicle stick because they can each conduct heat, but to varying degrees. As the utensils warm up, the butter on each of them is melted, which makes the candy fall off. The faster a candy falls off, the better a conductor its utensil is because the heat was able to travel through it more quickly.

70 Mini-Hovercraft Materials A large balloon Scissors Pull out cap (such as those found on water bottles and dish soap containers) Hot glue gun Hot glue sticks a CD Procedure 1. Heat the glue gun to its maximum temperature. Insert a glue stick into the gun. 2. Take the pull-out water bottle cap and cover the ring around the water bottle cap with hot glue. Align this cap against the hole in the center of the CD. 3. Press the cap against the hole firmly and wait for it to dry (do these last two steps quickly, while the glue remains hot). 4. Stretch the bottom of the balloon over the water bottle cap now attached to the CD. 5. Pull the cap outward on the water bottle and blow up the balloon (do this by flipping the CD over and blowing underneath the cap).

71 6. Close the cap of the water bottle to seal the air inside the balloon. Place the hovercraft on a flat surface. Then, pull out the water bottle cap. 7. The hovercraft should be able to be moved with very little force. When the balloon deflates, repeat steps 5 and 6. The Scientific Explanation The hovercraft travels easily because the air released from the balloon creates an air cushion below the CD and lifts the device slightly off the ground. This cushion of air helps to separate the hovercraft from the surface it s gliding over, which reduces friction between the mechanism and the surface. Less friction means less resistance, and this allows the appliance to travel longer distances with less force applied to it. In addition, the CD helps to keep the apparatus parallel to the surface it s traveling over, and distributes the weight of the craft over a larger area. This enables the hovercraft to be moved with a smaller amount of force.

72 Making a Series Circuit Materials 8 small pieces of solid wire 2 D-cell batteries 2 light bulbs from flashlights Electrical tape Procedure Take 4 pieces of wire, and tape each end to the ends of the batteries (so each battery has two wires on either side) Take the other 4 pieces and tape them to each contact on the light bulbs. Make a simple series circuit by attaching the battery wires to the light bulb wires in a loop. Why does the light bulb light up? Add another light bulb into the circuit. Does the first light bulb get dimmer? Why? Instead, try adding the second battery. Why does the light bulb get brighter? Try adding the light bulb back in, on top of the additional light bulb. Record your observations.

73 The Scientific Explanation Making a closed loop allows electricity to flow in a circular path. If the loop is open (if there is a hole), electricity cannot flow through to make a complete circuit. Think of this as a toy train set: if you make a closed loop with the tracks, the train can go around in a circle multiple times. However, if you remove a piece of track, the train cannot move. The battery provides the energy needed to push the electricity through the loop (that s why batteries die out). The light bulb gets brighter with additional batteries because there s more energy available. The light bulb gets dimmer with additional light bulbs because there s less energy available.

74 Lemon Light Materials A lemon A knife Stiff copper wire 10 Smooth test clips 4 U.S. pennies 4 Galvanized nails Wire cutters 2.4V LED light Procedure 1. Cut a lemon in half the longer way. 2. Cut each new lemon piece in half. There should now be four lemon pieces. 3. Make a small cut in the peel at one end of each lemon piece. 4. Push a penny halfway into the cut of each piece. 5. Push a nail several centimeters into the opposite end of each lemon piece. 6. Cut the wire into nine pieces of similar length using the wire cutters.

75 7. Using the wire cutters, crimp two test clips to each wire. There should be one clip at each end of each wire. 8. The negative side of the LED is marked by a flat edge on the bulb of the LED itself. Connect the negative side of the LED light to the penny of any lemon slice using a copper wire with clips. Attach a second wire to the nail of this slice and to the penny of any un-used slice. 9. Link all four slices in this fashion except the fourth slice. Connect the last wire end to the nail of this slice and to the positive side of the LED light. 10. Do you see a dim light in the LED? The Scientific Explanation A simple battery can be made by combining two different metals in an acid. Metals are good at transferring electrons (the negatively charged particles of an atom), and different combinations of metals have different ways of sharing electrons. An acid (such as citric acid, in the case of the lemons) simply helps electrons move. By linking the pennies and nails of the lemons with copper wire, a closed travel path is made for the electrons. Copper is a better conductor than steel, which means that it gives off electrons more easily than the steel. The steel in turn attracts the electrons that the copper releases. This is why the pennies are the positive sides of the lemon cells and the nails are the negative sides. Electrons leave the pennies and the overall charge at the pennies is positive. The steel nails receive the free electrons and take a negative overall charge. When the electrons flow from negative (an excess of electrons) to positive (a lack of electrons) across the LED device, it lights up.

76 Make Your Own Flashlight Materials AA Battery Aluminum Foil Small Flashlight Bulb Sticky Tape Procedure 1. Cut the aluminum foil into two rectangles of the same size. They should be about 5 centimeters by 3 centimeters. 2. Roll the rectangles of foil the long way so they become round 5- centimeter wires. 3. On each wire, press one end so that it appears to be flat. Then, roll the other end in your fingers so that it is pointy, round, and smooth. 4. Tape the flat side one wire to the negative side of the battery, and tape the flat side of the other wire to the positive side of the battery.

77 5. Tape the wire from the negative end of the battery to the metal on the bulb, and just touch (not tape) the wire from the positive end of the battery to the bottom of the bulb. 6. What happens when both wires are connected to the light bulb? What happens when just one is connected? The Scientific Explanation The electrical energy of the battery is really a constant flow of electrons, negatively charged particles. Electrons from the battery are able to flow through certain materials, such as aluminum. The small wire inside the light bulb heats when electrons from the battery pass through it. When the bulb is hot enough, it gives off its energy in the form of light, which is why it is called the light bulb. Electrons can only pass through a complete circuit, so if the wires are not connected the battery and the light bulb, the electrons cannot move and do not heat the wire in the light bulb.

78 Create a Compass Materials 100mL of water 2 Styrofoam plates 4cm needle 2cm needle 1cm x 2cm cylindrical magnet Procedure 1. Pour the 100mL of water into a Styrofoam plate. 2. Rip off a small and thin 2cm x 2cm piece of Styrofoam from the other plate. 3. Magnetize the needle by rubbing the pointed end of the 4cm needle on only one side of the magnet at least 30 times. 4. To test if the needle is magnetized, try picking up the 2cm needle with the 4cm magnetically. 5. Once of the needle is magnetized, float the small piece of Styrofoam on the water. 6. Place the needle on the floating Styrofoam and observe. 7. Congratulations! You ve just created a compass!

79 The Scientific Explanation In this experiment, the needle acts as a magnet. Because the needle is only magnetized at one point, that point is directed towards the magnetic North Pole. This creates a simple compass that is easy to make and use. The Styrofoam acts as a floatation device that allows the needle to turn easier because the needle does not float on water unless it is placed very carefully on the surface of water, which can be difficult.

80 Magnifying Lens Focus Materials LED Magnifying Glass Meter Stick Printer Paper Tape Pencil Procedure 1. Tape the paper to a window. 2. Hold the LED 50 cm away. 3. Hold the magnifying glass 5 cm from the window. Record this distance on the paper. 4. Turn off the lights. 5. Trace the circle of light. 6. Repeat with the magnifying glass 15 cm from the window. 7. Repeat with the magnifying glass 25 cm from the window. 8. Repeat with the magnifying glass 35 cm from the window. 9. Repeat with the magnifying glass 45 cm from the window. 10. What do you notice about the drawings?

81 The Scientific Explanation The light from the LED passes through the magnifying lens and is redirected towards a focal point on the other side. If the light hits the paper before reaching this point, a circle is formed. The closer the distance of the lens gets to the focus, the smaller the circle becomes. But after passing through the focal point, the circle of light will grow larger.

82 Growing Sugar Crystals Materials 3 cups of table sugar 1 cup of water Glass jar Pencil String Paperclip Spoon Coffee filter (optional) Food coloring (optional) Procedure 1. Tie one end of the string to the pencil. Make sure the paperclip is clean and then tie the other end of the string to the paperclip 2. Boil 1 cup of water. Make sure an adult is in the room or ask one to boil the water for you. 3. Once the water is boiling, add the 3 cups of sugar. 4. Carefully stir the sugar until it dissolves in the water.

83 5. If you want, you can add food coloring at this point to make your sugar crystals colorful. 6. Once the sugar is completely dissolved pour the mixture into a glass jar. Be careful, it will be very hot! 7. If you have extra mixture you can save it for later or throw it out. 8. Place the pencil with the string and the paperclip across the jar top so the paperclip and the string are underneath the water and sugar mixture. Make sure they don t touch the bottom or the sides. You can wrap the string around the pencil a couple times if the paperclip touches the bottom. 9. Put the jar in a place where it won t be disturbed. Wait a couple days to a week until you can see crystals on the string and paperclip. The Scientific Explanation If you look closely at dry sugar, you ll notice it consists of little cube-like shapes. These are sugar crystals. When you add sugar to water, the sugar crystals dissolve, and the sugar goes into solution. But you can t dissolve an infinite amount of sugar into a fixed volume of water. When you can t dissolve any more sugar, the solution is saturated. The hotter the water is, the more sugar you can dissolve in it. If you cool this hot mixture of sugar and water, the mixture is supersaturated because the water now holds more sugar than it could at this temperature before. In this experiment, the sugar and water mixture is supersaturated because we mixed in so much sugar while the water was boiling and then let it cool. As the solution cools and the water evaporates the sugar crystals come out of solution and collect on the paperclip and string.

84 Crystallizing Sugar Materials Water Sugar Popsicle stick Microwave oven Yarn Bowel Plastic cup Procedure 1. Boil one cup water in a microwave oven. 2. Pour 10 teaspoons water into plastic cup. 3. Add 10 teaspoons sugar to cup, one teaspoon at a time. Stir after adding each teaspoon. 4. Tie a piece of yarn to a popsicle stick. 5. Place the popsicle stick across the opening of the cup so that the end of the string is in the water. 6. Leave cup in a place where it won t be disturbed. Crystals should start to form after a few days.

85 The Scientific Explanation Sugar is made of cube shaped crystals. They are formed by a recurring pattern of molecular bonds. When you stir the sugar into the warm water, these bonds break apart, but only a certain amount of sugar can be mixed into the water. When there is too much sugar, it won t continue to dissolve. When you dissolve as much sugar as possible into the water, the solution is saturated. However, this state is very unstable, and the sugar molecules will begin to form crystals again. When the yarn is placed into the mixture, the crystals will have a place to form, and soon the yarn will be covered in sugar crystals.

86 Tension Bridge Materials 12 popsicle sticks Procedure 1. Place two of your popsicle sticks vertically on the table (these will be known as the legs) 2. Lay one popsicle stick across the top of these two, with a little bit of the two bottom ones still showing (1 st supports) 3. Place the same setup across from this pair of legs 4. Put four popsicle sticks on top of the 1 st supports 5. Lift the tops of the legs of one end 6. Slide one of the final popsicle sticks into the slot created here (2 nd supports) 7. Slowly lower this end of the bridge until it is only gravity keeping it together 8. Repeat the last 2 steps for the other side of the bridge

87 The Scientific Explanation The bridge is being held up by the tension that is formed by putting the 1 st and 2 nd supports in between the legs and the deck of the bridge. The weight of the deck pushes down on the legs, which are pulling up on the deck at the same time. The weight of the bridge is keeping it suspended; therefore, the only force acting on the bridge is the force of gravity.

88 Magic Pop Cans Materials String 2 222mL aluminum cans 1 straightedge with centimeter markings At least 2 large books greater than 20 cm tall 1cm diameter straw Procedure 1. Cut two strings, each 14 cm long 2. Tape end of one string to each can tab 3. Place books to equal height greater than 20 cm, 25 cm apart 4. Place straightedge across both piles 5. Tape can strings to hang 8 cm below straightedge 7 cm apart