Lesson 4: Making it Stick (Magnets)

Michigan Science Standard VI.1 Matter and Energy: All students will measure and describe things around us; explain what the world around us is made of; identify and describe forms of energy; and explain how electricity and magnetism interact with matter.

Elementary Benchmark 5: Describe interaction of magnetic materials with other magnetic materials and non-magnetic materials.

National Educational Technology Standards:

4.Technology communications tools

· Use technology tools (e.g. multimedia authoring, presentation, Web tools, digital cameras, scanners) for individual and collaborative writing, communication, and publishing activities to create knowledge products for audiences inside and outside the classroom.

Materials (per group)

· 2 bar magnets

· Horseshoe magnet

· Iron filings

· Piece of white paper

· Worksheet

Objectives:

1. Students will recognize that iron and iron-containing materials are attracted by metal.

2. Students will recognize that magnets have two poles.

Engage

Find some magnets around the room. In my classroom, we have magnets on the chalkboard at the front of the room. Ask the students: How does this thing (point to the magnet) stay on the board? When I try to stick the chalk on the board it just falls right off. Try to stick the magnet on the wooden desktop of a student desk. Why does this magnet stick to some materials but it doesn’t stick to other materials? Is it magic? How do we know if a magnet will stick to something or not? Today we are going to explore magnets working out of our science books.

Explore

Students will work in groups of four to experiment with magnets and magnetic fields.

Part 1

Step 1: Place one magnet on a desk and try to push it across the surface with another magnet without touching it. Next, try to pull one bar magnet across the desk without touching it. How many combinations can you find that work? Draw three combinations on your worksheet.

Step 2: Put each magnet inside a different plastic bag. Put one magnet flat on your desk. Put the piece of paper on top of it.

Step 3: Sprinkle the iron filings on the paper above and around the magnet. Sketch what you see on your worksheet.

Step 4: Carefully pick up the paper and pour the iron filings into the plastic cup. Set it aside.

Step 5: Put the two bar magnets on your desk with the ends about 2 cm apart. Put the piece of paper on top of the two magnets. Sprinkle iron filings on the paper above and around the two magnets. Sketch what you see on your worksheet. The ends of the magnets are labeled N and S; look and write down which two ends were facing each other.

Step 6: Repeat steps 4-6 with as many different pairs of ends as possible. Be sure to label which ends are facing each other in your sketches.

Step 7: Repeat steps 3 and 4 for the horseshoe magnet.

Part 2

On the back of your worksheet there is a table. Choose 5 objects from around the classroom, write these objects down in the first column. After you have chosen 5 objects, predict whether they will “stick” to a magnet or not and write yes or no in the second column. Test these objects with a magnet. Does the magnet have any effect on them? Write your results in the third column of the table.

Develop

In this experiment, you have seen the effects magnets have on different materials. On the magnets, you noticed that one end is marked with an “S” the other end is marked with an “N”. These letters indicate the poles of the magnet; the magnetic poles are the places where the pull of a magnet is the strongest. As you saw in step 1, the poles are either attracted to each other or repel each other. What happened when the same poles (N-N or S-S) were near each other? (They pushed each other away, or repelled each other.) What happened when opposite poles were near each other? (The magnets were attracted to each other.) We also saw these effects when we used the iron filings; when the same poles were near each other, the iron filings were pushed out to the sides. When opposite poles were near each other, there were lots of filings pulled between them.

Looking at the drawings you made of the iron filings, there is one thing that all the drawings have in common. The lines of the iron filings always curved out from one pole, around, and back to the other pole. This is due to the magnetic field, which refers to the way magnets exert force on iron-containing objects. Although you can see the effects of the magnetic field, the field itself is invisible.

Extend/Apply

Magnets are used in a lot of things that we see everyday, including:

· Compasses – The needle in the compass is actually a magnet, which spins around and stops when it is facing north. When you know which direction is north, you can figure out the other directions.

(Never Eat Sour Worms = North East South West)

· Cow Magnets – A cow magnet is put into one of the four sections of the cows’ stomach to attract bits of metal that could be harmful to the cows’ digestive system.

· Credit cards

· Speakers

· Televisions

· Computer disks

· Cabinet latches

· Hold roller coasters on tracks

· Produce patterns on audio tapes

Adapted from: Electrical Energy published Macmillan/McGraw-Hill School Publishing Company, 1993.