Experiment 1. Making Clay Float
Materials: 2 ounces of modeling clay ($2 at Hobby Lobby), pan of water.
Step1. Make clay into a ball. Show how it sinks.
Step2. Reshape into a small boat, no leaks! It floats!!!
Lesson: This illustrates the famous Archimedes Principle. Objects more dense than water sink; less dense they float. Reshaping the clay causes it to displace more water than the weight of the clay. This has the effect of making the clay less dense.
Experiment 2. The diving eyedropper.
Materials: empty soda bottle (label removed for viewing contents) with cap, eyedropper, water.
Step 1. Fill the bottle with water.
Step 2. Place the eyedropper in a bowl of water and force out most but not all the air.
Step 3. Carefully place the eyedropper in the bottle. If it sinks you must start over and squeeze out just enough air to make it barely float.
Step 4. Place the cap on the bottle and squeeze the bottle. The eyedropper will sink to the
bottom until you release your grip, then it will return to the top.
Lesson: This classic experiment shows how submarines dive and fish use their swim bladder. When the bottle is squeezed the air bubble in the eyedropper shrinks and thus increases its density. The density of the eyedropper-bubble combination now exceeds the density of the water and the unit sinks.
Experiment 3. Amazing air pressure.
Materials: Purchase a large suction cup from the cheap tool aisle of most hardware stores. 4 inch diameter one or larger works best. They are usually molded in orange plastic. About $5.
Step 1. Locate a smooth solid surface such as a counter top. Avoid glass because damage could occur.
Step 2. Place the suction cup firmly in position and activate using the handle or lever.
Step 3. Invite the “student” to attempt to remove the device.
Step 4. Unless a leak occurs between the surface and the cup the “student” will not succeed. Release the lever and they will now easily remove it.
Lesson: At sea level, atmospheric pressure exerts a force of nearly 15 pounds per square inch! A 4 inch suction cup will be held in place by over 100 pounds of air pressure. Airplanes use the pressure difference between the top and bottom of the wing to produce enough lift to carry a giant airliner!
Experiment 4. The fire extinguisher in your kitchen.
Caution! This experiment involves matches and fire. Adult supervision required!
Materials: Large mug or measuring cup, small deep bowl, votive candle, matches, baking soda, vinegar.
Step 1. Place candle in bowl, light.
Step 2. Place a heaping tablespoon of baking soda in the mug.
Step 3. Be ready for action. Slowly pour about 2 tablespoons of vinegar in the cup. As foaming begins gently pour the “air” out of the cup and into the bowl. Do not pour any liquid into the bowl. The candle will go out.
Lesson: A chemical reaction between baking soda and vinegar produces carbon dioxide, an orderless gas we exhale. CO2 is heavier than air and will displace air in the bowl. Fire needs oxygen in the air to burn. CO2 starves the flame.
Note: This experiment needs calm air. Turn off fans and move away from open windows.
The above experiments are fun for kids despite any detailed explanation. However, in the spirit of helping (grand) children develop a deeper appreciation of the underlying scientific principles please refer to page 2. Use judgment, based on the age and maturity of the youngster. Too much talking can turn an eye-catching demonstration into a tedious lecture. Science can be fun don’t spoil it.
Developing an Understanding of
and a Love for Science.
By nature we are curious animals. Human history is filled with man’s quest for knowledge. As a (grand)parent you may be at a teachable moment with your offspring! Seize the opportunity but avoid overkill. Encourage questions but be honest if you don’t know. Today, internet searches can make you look like a genius! You are to be commended for your efforts. Good Luck!
What follows are like those “Learn More” boxes in “Science for Dummies” books.
Making Clay float experiment. The key concept here is buoyancy (floating and sinking). This principle is found extensively in nature and is used frequently in research and technology. It works because when fluids in a gravitational field have objects (or other fluids) contained in them, a natural sorting process occurs, depending on the relative density of the fluid to the object. i.e. heavier objects sink and less dense ones float. In the case of the toy clay boat we “trick” nature into thinking the clay is less dense than the water by shaping it to include some air which of course is way less dense than water. Mixing oil and water will always result in the oil floating on top of the water because its’ density is less than water.
The diving eyedropper. This experiment, like the floating clay experiment dabbles in the principle of buoyancy but with a clever twist. Unlike the clay boat which will only float at the surface the diving eyedropper is actually like a miniature submarine, capable of both floating at the surface, diving to the bottom and returning to the surface. Pretty clever, huh? Here’s how it works. The cap must be on the bottle! Depending on the manufacture of the eyedropper you may or may not be able to see the air bubble in the glass tube. (Some mfg. use thicker glass, thinner rubber cap, etc.) When the bottle is squeezed the pressure everywhere in the bottle increases. Water is not compressible but the air bubble is. Squeezing shrinks the air bubble increasing the density of the entire assembly. Squeeze it enough and the density is greater than the water and the “diver” dives. Relax you grip, the density is reduced and the diver floats back up. It’s that simple!
Suction cup demonstration. (Amazing Air Pressure) This experiment will not work on the moon, should you ever travel there! The earth’s atmosphere is approximately 20 miles deep. Air molecules can be found at a hundred miles or further but they are very scattered. Each molecule, despite its’ small size, has some weight. In addition, gas molecules (air is a mixture of approximately 20% oxygen and 80% Nitrogen) are like tiny springs. As they stack up 20 miles the bottom ones are tightly packed and exert a pressure of about 14.7 pounds per square inch at sea level. Therefore one square foot of table top, body flesh, rock, etc. has over a ton (2,000 lbs.) of pressure on it. The suction cup works by creating a sealed chamber on its back side and reducing the pressure inside. This is done by a flexible rubber diaphragm that can be flexed away from the supporting surface thus reducing the internal pressure by “spreading out the molecules”. If a “perfect vacuum” were created behind the suction cup the pressure differential between the front and the back could be as much as 180 lbs. or more. Even with a partial vacuum created by moving the “locking handle” it’s probable that a force of up to 100 pounds might be required to break the seal!
Fire extinguisher in the kitchen. The experiment is pretty much self explanatory. Fire is a rapid chemical reaction requiring oxygen. Combining baking soda and vinegar results in rapidly creating the gas CO2 or carbon dioxide. Because CO2 is more dense than air it readily sinks. Although invisible if you carefully create a short trough with a folded piece of paper you will be able to pour the invisible CO2 down the trough (slope it about 45 degrees) and extinguish the flame. It may take a few seconds for the CO2 to reach the flame. It pours more slowly than water. In case of a real fire please use your real kitchen fire extinguisher!
(Paul Lupton, Park Place TX 2012)