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Introduction

Outreach Programs for K-12 Students

Fun, Easy Experiments
Fun, Easy Experiments


Learn more about:
The Terrella, an Eighteenth Century Idea for the Modern Classroom
The Everglades Experiment
Ice Race
Milk Bubbles
Rolling Bottles
The World of Density: Water, Oil and Ice


The Terrella, an Eighteenth Century Idea for the Modern Classroom

A wonderful way to gain insight into many basic ideas relating to the sun and Earth connection is to set up an old-fashioned terrella (little Earth) on a sunny windowsill or outside where it can be in the sun much of the day.

Begin with any globe (an inexpensive one is fine. . . . I have a 10" diameter globe but smaller works as well) and remove it from any mountings. Insert something at the N and S poles to make them obvious and insert a pushpin where you live. (I have inserted a dowel through the globe and fine it very handy for twirling the globe when I want to show rotation.)

Submitted by
Ms. Charlotte (Tay) Tahk
Nativity of Our Lord School
Orchard Park, New York

(adapted from C.L. Stong, The Amateur Scientist; Simon & Schuster, NY 1960 (a collection of the old Amateur Scientist columns from Scientific American)

Determine the direction of North wherever you want to keep the globe and orient the globe so the N pole is pointing North, then rotate the globe in the plane of your longitude line so that your pushpin is pointing up and the N pole is still pointing North. If you have other locations you want to keep track of or feel connected to, insert push pins there too, but they won't point up. . . . I have pins in Hawaii where my parents live; in Riga, Latvia where my daughter was an exchange student; and in the Galapagos Islands where I let Charles Darwin (known in my classroom as Charlie) be our observer on the Equator when we need one.

Place the globe on a base in the sunshine (I use a large plastic jar that contains the penny collection I use for other experiments). Now how do you use it?

The essential point is that when you orient it this way, it's set up just as the Earth really is with respect to the sun. (I tell my classes it's the way the Earth would look to an astronaut looking back to earth.) Some parts of the globe are lit up by the sunshine so those parts of the Earth are having daylight now. Some parts are in the dark, so it's night there. Some parts are right at the light/dark border so they are having dawn or dusk. Is it sunrise in the Rockies or evening in England? Interesting to use it to estimate the time of day at different locations right then and good for general discussion of time zones.

But that's just what you can see at one time. What's most interesting to me is to watch over the course of the year. For example, on the equinoxes you will see the light/dark lines split the globe exactly in half . . . nights are 12 hours long everywhere. As the seasons progress you can see days lengthening or shortening; near the winter solstice you can see something that seems to interest students very much . . . why there are days when the sun doesn't rise North of the Arctic Circle. And the reverse of seasons between Northern and Southern hemispheres is immediately obvious!

You may also view the Earth from many cities in the world at http://www.fourmilab.ch/earthview/vplanet.html




The Everglades Experiment

Have you ever been to the Everglades? One of the most important things in the Everglades is water. There is a very delicate balance here, since the Everglades rely on the same water sources used by Miami and other cities, area farmers and industry. That makes it very important for people in this area to conserve water, but water conservation is important everywhere. Most people have no idea of how much water they waste every day. To give you an idea, we are going make a few tests.

You will need:

water
measuring cups

Even little things can make a big difference in conserving water. You would be amazed how much water goes down the drain for something as simple as a dripping faucet. To see how much water this can waste, turn on the water faucet just enough to get a steady drip, drip, drip of water. Place the measuring cup under the faucet. Now wait for 15 minutes. Turn off the water and look to see how much water you collected. Multiply this by 4 and you will see how much drips away in an hour. Multiply that by 24 and you have how much drips in a day. Multiply that by 365 and you have a year's worth of drips, which is a lot of water.

Submitted by
Ms. Louise Nolan
Assistant Superintendent for Curriculum & Instruction
Woburn Public Schools, Massachusetts

Created by Robert Krampf

Next its time to brush your teeth. Do you leave the water running while you brush? If you do, place a large bowl under the faucet when you brush your teeth. When you finish, use the measuring cups to see how much water ran down the drain while you were brushing. Multiply that by the number of times a day you brush your teeth. Then multiply that by 365 for a year's worth of tooth brushing. Again, over a year it is amazing how much water is wasted this way. Place the empty pan back under the faucet. This time, turn the water on long enough to wet the toothbrush and then turn it off. Turn it on only when you are using it. Measure to see how much you saved. Over a year, that could be a lot of water, especially if you have several people in your family.

There are many things that you can do to use water more wisely. For example, instead of pouring the water you use in these experiments down the drain, pour it on potted plants or flower beds that need water anyway. Every little bit helps. Look around your house to find all the ways that you use water. Can you figure how many gallons your family uses each day? If you look at your utility bill, you should be able to get an idea of how many gallons you use each month. Multiply that by 12 and you get an idea of how much you use each year.




Ice Race

You will need:

a wide, plastic container
a small plastic cup
water
a freezer

Fill the small plastic cup with water and pour it into the wide plastic container. Fill the cup again. Place the container and the small cup into the freezer. While you wait for the water to freeze make a guess about which you think will freeze first. Wait a minute! They both have the same amount of water, don't they? Doesn't that mean that they will both freeze at the same rate? Take a quick peek every 15 minutes until one of them is completely frozen. Which one froze first?

Answer:

The water in the wide container froze much faster. Why? Even though they both have the same amount of water, they are in very different shapes. The water in the wide container is much more spread out. It has a much larger surface. The surface is where the heat is transferred, so the more surface area, the faster the heat will be transferred and the faster the water will freeze.

Submitted by
Ms. Louise Nolan
Assistant Superintendent for Curriculum & Instruction
Woburn Public Schools, Massachusetts

Created by Robert Krampf

You can see the same thing in reverse. Let the cup and the wide container stay in the freezer overnight, to be sure they are both well frozen Remove them and place them on the table. Wait and check them periodically, to see which one melts first. Which do you think it will be?

Right! The wide container melts faster, again because it has more surface area.

Now, think about what this might have to do with something like cooking. Think about cooking potatoes. Imagine if we had a pot of boiling water and two potatoes. If we put one potato in whole and cut the other into one inch cubes, which would cook faster? The cubes, right? Cutting the potato into pieces means more surface area, which means it cooks faster. That is why we often chop vegetables before we cook them. It lets them cook faster and more evenly.

I like cooking and it is even more fun when you can see the science in it.




Milk Bubbles

You will need:

a glass of milk that is half full
a glass of water that is half full
a soda straw

The start is easy. Put the straw in the glass of milk. If the glass is more than half full, use the straw to drink the excess. Then blow gently through the straw, making bubbles in the milk. Continue doing this until you fill the glass with bubbles, or until your mother tells you to stop playing with your food and get ready for school.

It was pretty easy to fill the glass with milk bubbles. Next, try the same thing with the glass of water. This is not nearly as easy. The bubbles pop very quickly, making it difficult to fill the glass with bubbles without blowing so hard that you make a mess. Why the difference? The milk contains milk proteins. These proteins form a film in the bubble which makes it stronger. The protein film lets the bubbles last long enough to fill the glass. The amount of milk fat can also have a big impact on this. Liquid milk fat forms films in the bubble more easily than the milk protein, but it forms weaker bubbles. Low fat milk tends to make stronger bubbles than whole milk.

Submitted by
Ms. Louise Nolan
Assistant Superintendent for Curriculum & Instruction
Woburn Public Schools, Massachusetts

Created by Robert Krampf

Temperature also has an impact. With a glass of cold milk, the bubbles were large and lasted quite a while. As the milk warmed up to room temperature, the bubbles were smaller and popped quickly. This means that you should blow your milk bubbles early in the meal, instead of waiting to blow bubbles with your dessert.




Rolling Bottles

You will need:

2 soda bottles with screw-on caps
water
sand or dirt

Fill one of the bottles with water and put the cap on tightly. Fill the other with sand or dirt or potting soil if it's raining outside. Put the cap on that one too.

Now for the fun part. Find a long hallway or room with lots of open floor. Roll the dirt filled bottle. Notice how far it rolls and the way that it behaves. Then roll the water filled bottle. Try to use the same amount of push to get it going. Does it roll the same distance? Does it stop in the same way? OK, now stop and don't read any more until after you have tried this and thought about it.

What happened?

Submitted by
Ms. Louise Nolan
Assistant Superintendent for Curriculum & Instruction
Woburn Public Schools, Massachusetts

Created by Robert Krampf

The bottle with the dirt rolled farther. It gradually slowed down and finally stopped. The bottle with the water started rolling just fine, but it slowed down very quickly instead of gradually and did not roll as far.

Why?

The bottle with the dirt acted like a solid. As it rolled, all of the dirt rolled with it. It behaved just as we would expect it to. With the bottle of water, things are very different. When you roll the water bottle, the bottle rolls but the water in the center does not. Friction causes some of the water along the sides of the bottle to move with it. The friction between the bottle and the water, and then between the spinning water and the water in the center slows the bottle and stops it from rolling. You can test this by swirling the bottle before you roll it. This gets the water spinning so that it will all move with the bottle. In this case the bottle behaves much more like the one full of dirt. The water is moving along with the bottle, so there is less friction. Be warned that if you swirl the water in the wrong direction, there will be more friction and it will stop even faster than it did unswirled. OK, now that you have read it all, you can go try it. knew that you would not be able to wait until after you did the experiment.




The World of Density: Water, Oil and Ice

Let's explore the world of density. This is a very useful science, important for many things from boats to hot air balloons.

You will need:

a tall, clear drinking glass
cooking oil
ice

Fill the glass almost full of cooking oil. I found that cheap, vegetable oil worked very well. Canola oil did not work at all, as it was not dense enough. Place the glass of oil on a flat surface and then gently add an ice cube. The ice should float. If it does not, try using a different kind of oil.

Now comes the interesting part. Oil floats on top of water and ice floats on top of oil. What will happen when the ice begins to melt? Watch a minute or two and you will see. As the ice begins to melt, you will see a drop of water hanging from the bottom of the ice cube. As the drop grows, the ice cube will float lower, as it is being weighted down by the denser water. Finally, the drop gets large enough to pull free of the ice and it slowly sinks to the bottom of the glass.

Submitted by
Ms. Louise Nolan
Assistant Superintendent for Curriculum & Instruction
Woburn Public Schools, Massachusetts

Created by Robert Krampf

Water is a strange chemical. Most liquids get smaller when they freeze, which means the solid form is denser. When water freezes, it gets larger. It still weighs the same, but it takes up more space, which means it is less dense. That is why ice floats in water, and in the oil. If something is denser than water (or in this case, oil), it sinks. If it is less dense than the liquid, it floats. As the ice melts, the water takes up less space, becoming denser, and the denser drops of water sink to the bottom of the glass.

After the ice had all melted, I tried reversing the process by putting the glass of oil and water in the freezer. was hoping that I would find a lump of ice floating on top of the oil. Instead, the lump of ice was at the bottom. As the water began to freeze, the surface tension of the water was strong enough to keep the ice from rising up through the oil. Soon, it froze to the side of the glass and then was firmly trapped at the bottom. I did manage to gently warm the glass and get the ice to come free and float to the top. If you try that, be sure to warm the glass slowly, so it does not crack.


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