It is always a good idea to begin by assessing what students know about as subject. In this case most third graders have had experiences with magnets. It cannot be stressed enough that students need plenty of opportunities to "play" with the magnets. Since my students already have experience with magnets it would be beneficial to do a class KWL chart. That is a listing of what they know, what they want to know, and what they learned about magnets during these preliminary explorations. This would help teachers to see what experiences students need to increase their level of knowledge. At this point it is perhaps not even necessary to give things specific names or use correct terminology, but to allow children to draw their own conclusions. Children need to begin keeping their journals of what they do and what they see. They should also be encouraged to draw diagrams and pictures of what they observe. In this way they are like Thales the philosopher/scientist who used observation as his basic tool.
Activities: There are many readily available resources that will give many suggestions for experiments. I would like to offer three.
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1. What do magnets attract? This is a very basic experiment but can easily help to assess that students know the basics of how a magnet works. Students can complete a chart listing a group of items and whether they are attracted to the magnet or not. Students should be encouraged to add objects to the list. How powerful is a magnet? Students should be given the opportunity to work with a number of different magnets and to test how many paperclips the magnet can hold.
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2. Students will hopefully discover that size does not predict the power of a magnet.
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3. How can you make a magnet? Students can be given thicker blunt needles and shown that if they rub a magnet on the needle going in the same direction for around 50 strokes that the needle will become magnetized.
After some work on magnetism students need to think about another force Thales dealt with called static electricity.
Activities: In a simple experiment students can use a comb to rub on their hair or clothes to see if they can make the comb into a kind of magnet which will attract scraps of tiny paper or plastic wrap. Is the comb a magnet?
If there is nylon carpeting in the school or the teacher has a small rug scrap the children can then try rubbing their feet and then touching a metal doorknob where they will get a shock and possibly see a spark.
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1. Blow up two balloons and tie a string to each. Rub them on a piece of wool (Someone may be wearing a wool sweater, which works just as well). Lift the two balloons up by the string and you will find that they float apart. Perhaps they are like the poles of a magnet. If you put a stiff piece of paper in between the balloons, they will be attracted to the paper and both will collapse toward it. Pull the paper away and the balloons will fly apart. Here the balloons are indeed acting like the two ends of two bar magnets.
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2. Can a balloon bend water? Take a balloon and rub it against apiece of wool. Hold it near a stream of water from a tap and you will see the water will bend toward the balloon. It the balloon gets wet the water will stop bending. This is a good place to do a comparison chart of the similarities and differences
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between magnets and static electricity.
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3. How can you make a magnet? Take a blunt needle and have students magnetize it as done in a previous experiment. Then attach the needle to a cork. Float the cork in a bowl of water and students will see that the needle will tend to float in one position. If compared to a conventional compass it will be obvious that the needle is pointing in a north, south position.
Background:
People have always been aware of electric energy whether it was from lightning, the sting used by certain fish to sting their prey, or the spark they felt when they rubbed certain materials together. Thales, who was a Greek philosopher (640 to 546 BC) is the first person to have left his recorded observations concerning static electricity and magnetism. He observed that when he rubbed a piece of the stone amber with a cloth it attracted bits of straw. The Greek word for amber is elektron from which the word "electricity" would later come.
Some three hundred years later the Chinese general Huang-ti was suppose to be the first to use lodestone as a compass. The Chinese had found that the stone was more precious than a group of jewels because it had three magical qualities. First it attracted iron. When the stone was first found in Europe it was near the Aegean Sea near the region of Magnesia. Our word "magnet" comes from this early name. Second when the stone was placed on a wooden raft in a bowl of water it always turned until it was pointing north- south. One side always pointed toward the North Star, which never changed positions so it became important for guiding sailors. Since it could help lead the way on a cloudy night it was called "lodestone" or stone that leads. The third peculiarity of this stone was that you could transfer its powers to an iron needle. Instructions for doing this were written down some fifteen hundred years ago by the Chinese.
The lodestone was not used for navigation until around the thirteenth century AD, which corresponds to the time when Marco Polo was exploring the Far East. Arab sailors saw the advantage of using a compass and they are the ones credited with bringing it to Europe. Sailors no longer would have to hug the coast when they sailed for the compass could easily allow them to get out into deeper waters. Christopher Columbus was undoubtedly using a compass when he crossed the Atlantic looking for a quick route to the Indies.
It is important for students to know that the finding of the lodestone was purely accidental but that it led to much progress in transportation. Astronomers had identified the North Star and it was very useful to navigators in planning their journeys. Still up until the development of the compass ships usually hugged the coastline and on cloudy or stormy nights navigation was impossible. The finding of the lodestone and the making of the compass changed everything. Ships could still navigate in cloudy weather because they no longer had to see the North Star the compass would point to it for them.