Overview: Students will play and discover using a solid material, magnets!
Vocabulary: Magnet, magnetism, magnetic, metal, solid, North, South, attract, repel, iron
Objectives: Students discover the concept of magnetism and learn what things around them are magnetic.
Materials: Coins, paper clips (other various objects both magnetic and not), a variety of magnets, large powerful magnet, figs, grapes, apples, chopsticks, string, small stand, "magnetic or not" worksheet, matches
Resources: Youtube Video of "amazing tricks with magnets"
The Lesson:
- Open with review of the states of matter (solid, liquid, and gas). Ask the students to give an example of each. Ask the students what they learned about the properties of the gas air. Ask students what they learned about the properties of liquid water.
- Explain today we will be doing activities and experiments with solid materials, specifically in the form of magnets.
- Ask students what a magnet is. What kinds of things are magnetic.
- Review that a force is a push or a pull. Ask which of these two things magnets do (both). See if students connect that magnetism is an example of a type of force.
- Depending on the age of the students, do a "magnetic or not" activity. Students will be put into pairs. With their partner they will use a magnet to test various items in the classroom. They will mark on their worksheet which items they tested, as well as the result if the item was magnetic or not. If students are older instead have them play with polar magnets. Ask them to also observe which ends of the magnets are attracted to each other and which end are repelled by one another.
- Have each pair share a result they found interesting with the class.
- Show the "amazing tricks with magnets" video. Don't show the portion with the fruit being 'magnetic'
- Now tell the students you are going to do some "magnet magic" in class.
- First do a simple demonstration with matches. Show the students that new matches are not magnetic. Let a student come up and try so they know you are not tricking them in any way. While wearing the proper safety material, light a handful of matches, allow them to burn a few seconds, and then put them out. Now the burnt matches will be magnetic!
- Allow the students time to be in awe. Show again how the new matches aren't magnetic but the burnt ones are. Let the students shout out guesses as to why. This is a more advanced concept so they might not guess, but here is the answer. The heads of most matches contain iron oxide. When you light a match the fire the iron oxide is reduced, carbon oxide released, and ferromagnetic iron remains on the match head. This is more magnetic than the iron oxide was, so the magnet is able to lift the burnt matches. Be sure to test the matches before you do this experiment. Not all matches contain iron oxide in the match head, so won't work.
- Before the class have constructed a stand with an 'arm' able to support a horizontally suspended chopstick with string. The chopstick should be able to rotate freely.
- Show the students a fig. Ask them what it is. "Is it magnetic?" The students should say NO. Demonstrate how a magnet doesn't stick to a fig.
- Place the one fig fruit on each side of the chopsticks. Slowly approach the fig with the magnet but DO NOT actually touch the fruit with the magnet. The fig should very slowly move away from the magnet, causing the chopstick to rotate. Move the magnet to the other side of the same fig, or to the other fig on the opposite side. This should cause the chopstick to stop rotating.
- Ask the students how this is possible. Let them discuss it in small groups and present their theories to the class.
- Repeat the demonstration with a grape. Show first that the grape is not magnetic. Then place one grape on either end of the chopstick. The chopstick should rotate faster than it did with the fig fruit.
- Now reveal the answer to how this is possible. Some matter is diamagnetic. Simply put, this means that the matter is repelled by both ends of a magnet. Water, a main component of fruit, is an example of a diamagnetic material. Friction from the table prevents the fruit from moving away from the magnet when students were testing to see if it was magnetic. Only when the fruit is suspended, and therefore friction reduced, is the fruit able to move away from the magnet. This force is a very weak force, explaining why it is often passed over when studying magnets.
Homework: What other fruits could you use for this same experiment? Which fruits would work the best? Bring your fruit to the next class to test!
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