Magnets: They Are Totally Attractive
Grades 6-8

In this lesson students will be able to classify objects that magnets are attracted to and aren't attracted to, and students will magnetize metal. Students will also construct and use a compass. This lesson will culminate with students developing one of several possible products that will illustrate their understanding of magnetism.

Take a Look II: Magnets

To get a copy of the video, please contact:

TV Ontario
(919) 380-0747

(Utah Core Standard 3050-0104)

Students will be able to:

• Observe and describe the effects of Earth's magnetic field.
• Construct and use a compass.
• Research historical uses of magnets.
• Make observations.
• Classify objects.
• Predict results of experiments.
• Make inferences about magnets during and after completing activities.
• Make comparisons.
• Communicate predictions, inferences and the results of investigations.
• Experiment with magnets in various ways.

Timing:
Two 50-minute class periods.

Per student:

• Science journal

For every four to five students:

• Various sizes and types of magnets
• Paper clips

For every three to four students:
Small objects made out of:

• aluminum
• glass
• nickel
• plastic
• steel
• rubber
• copper
• wood

For every two to three students:

• Large nail
• Small tacks
• Sewing needle
• 1-inch square piece of styrofoam such as a meat package
• Bowl of water
• Compass

Background:
Magnetism is caused by electric charges that are moving. Moving electric current is inside a bar magnet. The electric charge is a constant part of the magnet. The electric current produces a magnetic field.

The molecules in a nail or needle are randomly arranged. We can make nails or needles into magnets by stroking them in one direction many times with a strong magnet. The stroking forces the molecules to align themselves in one direction. Magnets can lose their magnetism when they are dropped, heated, or hit hard with a hammer. These actions cause the iron molecules to become unaligned.

The ends of magnets are called poles, and every magnet has a north pole and a south pole.

In order to introduce the concept of magnetism and make the video segments more meaningful, begin by having the students participate in the following activities:

Assign each student a partner. Pass out a bar magnet to every student, and have them explore how the magnets work together. Ask, "Do you notice anything interesting about how your magnet acts with your partner's magnet?" Students will probably answer that the magnets are attracted to each other sometimes, and at other times they aren't. Ask, "Why do you think this is true?"

If the students don't come up with the correct answer, explain that every magnet has two poles, a north pole and a south pole. The poles are on the ends of the magnets. The poles have to be different for the poles of two magnets to touch. Remember the phrase: opposites attract. The north pole wants to be next to the south pole because they are opposites.

Now ask, "Do you think one part of the magnet is stronger than the other parts of the magnet? Which part do you think will be stronger?"

Pass out several paper clips to each set of partners. Say, "Spread out the paper clips on your desk, and place the magnet on top of the paper clips and lift." Ask, "What parts of the magnet are the paper clips attracted to?" Say, "Count how many paper clips are stuck to each pole of the magnet. What part of the magnet had fewer paper clips stuck to it? What does this tell you about the magnet?"

To provide a focus for viewing, say, "We are going to watch a short video segment on magnets. Be ready to tell me how a magnet helped Kate."

PLAY the video.
PAUSE the video when Kate says, "Why don't you sort them into two collections?"

Ask, "How did a magnet help Kate?" [The magnetized screw driver helped her get the screw she had dropped between the planks of wood.]

Say, "Now we are going to do the same classification activity as Jamie." For every three or four students, pass out small objects made out of these materials:

• aluminum
• glass
• nickel
• plastic
• steel
• rubber
• copper
• wood

Say, "First I want you to predict which objects you think the magnet will attract." Give the students 3 or 4 minutes to do that.
Say, "Let's watch the next segment of the video. Check your prediction with Jamie's."

RESUME the video.
PAUSE the video after Kate says, "Why don't you test them?"

Pass out a magnet to each group. Say, "Now, let's find out which materials the magnet attracts." Allow 3 or 4 minutes for the students to complete their test. Say, "Let's check your findings with Jamie's."

RESUME the video.
PAUSE the video after Kate says, "I will record the results, and you try the rest."

Say, "Let's brainstorm individually the many and varied uses for magnets. Write your ideas in your science journal." Allow 4 or 5 minutes. Say, "Now get with your small group and check your ideas with your group members' ideas. You may add any new ideas to your list." [Some uses include: Video and audio cassette tapes are made with plastic that is magnetized. Hard and floppy disks store data with magnetized coatings. All compasses have a magnet inside that lines up with the Earth's magnet.]

Say, "Watch the next video segment and check to see if they mention other uses for magnets that you didn't think of."

RESUME the video.

STOP the video when Kate says, "But you can probably find magnets a lot closer to home. Try the fridge, or the fridge of one of your friends."

Explain to the students that they are going to create a model of a magnet. Say, "Let's examine what a magnet is. A magnet is any substance or object that can attract iron or other magnetic materials. Each magnet has two poles. Magnetic poles have properties similar to an electrical charge. Poles with the same character always repel, while opposite poles always attract (north attracts south but repels north)."

Pass out the following materials to every two to three students:

• Large nail
• Bar magnet
• Small tacks

Say, "Test your nail by touching it to the tacks. It should not pick them up. Next hold the bar magnet in one hand and stroke the nail across it. Be sure you stroke it in one direction only. Stroke it around 50 times. Test your nail by touching it to the tacks. The nail should pick them up now."

Explain, "Magnetic materials such as iron have microscopic regions called magnetic domains. Each domain acts like a tiny bar magnet with a north and south pole. Normally, the material has its domains arranged randomly. When the domains are lined up, their north poles all face the same direction. This is what happened when we stroked the nail with a bar magnet; we lined up the domains. Scientists say that the material has now been magnetized - or turned into a magnet."

Ask, "How do you think we can demagnetize the nail?" Allow for predictions. Have the students drop the nail several times, and this will force the domains to be in random order and no longer magnetic.

Explain to the students that each group is going to make a water compass.

Provide each group of 3 - 4 students with these materials:

• 1 sewing needle
• 1 1-inch square piece of styrofoam such as a meat package
• Bowl of water
• 1 bar magnet
• 1 compass

Explain and demonstrate the following directions for making a compass.

1. Stroke the needle 40 times across the magnet, in one direction only.
2. Float the styrofoam on the water, and gently lay the needle on top of the styrofoam.

Direct the students to observe the needle. You may wish to have the students write their observations of the movement of the needle in their science journal.

Have students speculate on what is happening. [The biggest magnet is the Earth. There's even a North and South Pole, just like the north and south poles of a magnet.]

Have the students compare their water compass with those made by other groups. How are they similar? How are they different?

Direct the students to compare their water compass to a pocket compass. How are they similar? How are they different?

Change some variables. Try using larger and smaller needles, weak magnets versus strong magnets, different liquids, or paper clips instead of needles. Design experiments testing each variable and hypothesize the results. What materials make the most effective compass? the lightest?

Invite an airline pilot, sailor, field guide or another professional to the classroom to discuss and/or demonstrate the importance of a compass to his or her job.

Have students research two or three of the following common misconceptions about magnets and write a short paragraph explaining why the statement is not true. Be sure to have them include where they got their information and cite any resource materials they may have used.

1. All metals are attracted to a magnet.
2. All shiny, silvery objects are attracted to a magnet.
3. The larger a magnet is, the stronger it will be.
4. The magnetic pole located near the earth's north pole is an N pole.
5. A magnetic field can only come from a magnet.
6. A magnetic field is a pattern of lines and not a field of force.
7. Magnets have charges.
8. The north pole of a magnet has a positive charge.

Build an electromagnet using a D cell, a large steel nail, and about 50 cm (20") of insulated wire. Strip the insulation off two ends of the wire, and carefully wrap the wire around the nail to form tight coils. Don't overlap the coils, and make sure that you leave at least 6 cm (2.4") of wire free at each end. Connect the two ends of the wire to the two ends of the D cell, and bring the tip of the nail very near some metal paper clips. The magnet will only attract if the circuit is complete.

[Background information: An electromagnet is a temporary magnet formed when electrical current flows through a wire or other conductor. Most electromagnets consist of wire wound around an iron core. This core is made from magnetically soft iron that loses its magnetism quickly when the electric current stops flowing through the wire.]

Mathematics:
Introduce compass use in mathematics. Provide the students with a compass and have them write directions to another part of the school building using North, South, East, West coordinates. Have students trade directions with another student and try to follow the steps provided.

Japan and Germany are building magnetic trains that hover over the rails. These trains can move up to 480 kilometers (300 miles) per hour. Compare those speeds to the speed of trains in the United States. Graph the data.

Language Arts:
Students can write about experiences with magnets. Have students think of and write down as many things as they can that use magnets, or have magnets in them.

Read the following books about magnetism:

Jason Cooper, MAGNETS, Rourke Corporation, 1992.

Irving and Ruth Alder, MAGNETS, John Day Company, 1966.

Research Skills:
The first known magnets were hard black stones called lodestones. Ancient Greeks knew of the lodestone's power to attract iron. In 1820, Danish physicist Hans Oersted discovered that an electric current produces a magnetic field. Have students study the early use of the magnet and electromagnet.

Ever wonder why the Earth has a North and South Pole? Students can research this topic and share their findings with their classmates.

Social Studies:
Incorporate the use of the compass in geography.

Art:
Draw a maze on a paper plate for another student to try and follow, using one magnet above and one magnet below the plate.

Internet:
Science of Magnets - Learn about the history of magnets and the importance of electro-magnetism. Try http://buerkle.arc.leon.k12.fl.us/MAG/magtext.pg14.html

Magnet lesson plans can be found at: http://www.calvertnet.k12.md.us/instruction/lessons/magnets/magnet.html

Measure the magnetism of the earth. This is a project that can involve students from around the world. Using an educational newsgroup or an educational listserv, invite other classrooms with electronic mail to join your class in collecting data.

Materials for every pair of students:

• 1 bar magnet
• 1 blunt sewing needle
• Silk thread (about 18 inches long)

Each pair of students must use similar material to ensure consistent experimental conditions. Be very specific about the kind of needle, thread, and magnet used.

First, tie one end of the thread around the middle of the needle, making a tight knot. Magnetize the needle by stroking the needle with the bar magnet 50 times, going lengthwise and always in the same direction.

Next, hold the end of the thread so that the needle is suspended in front of you. Make sure that the needle is well magnetized by checking to see that it points north-south. Carefully turn the needle 90 degrees so that it is pointing east-west. Let go of the needle and immediately begin counting oscillations. Continue counting for one minute. Each oscillation will include a full cycle of movement - the needle will begin and end in the same position.

The number of oscillations provides a relative measure of the Earth's magnetic field. A large number of oscillations indicates a strong magnetic field; a small number indicates a weaker one. Students who perform this experiment near the North and South Poles will measure a stronger magnetic field than students near the equator.

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Master Teacher: Karen Krier