What Is a Magnet? 20 minutes. Materials For the class. 2 pc. aluminum foil 2 brass brads 16 index cards 2 pc. magnetite

Transcription

1 Share with Your Students What Is a Magnet? Vocabulary magnet a material that attracts steel, iron, cobalt, and nickel Magnets come in many shapes and sizes. that contain iron, steel, nickel, and cobalt are attracted to, or pulled toward, a magnet. Magnets also attract the mineral magnetite and other magnets. that are attracted to a magnet are described as magnetic. STUDENT RESOURCE 1.1 INFORMATION SHEET magnetite a mineral that is naturally magnetic Magnetite contains iron and is a weak magnet. Early explorers used magnetite to find rth. Magnetite is sometimes called lodestone. 1. Make copies of Student Resource 1.1, Vocabulary, and distribute to students. Discuss the definitions with students as terms come up throughout the section. 2. Ask: What is a magnet? (a material that attracts steel, iron, cobalt, and nickel) Survey the class to find out how many students have used magnets. Discuss how the magnets are used. (Likely responses will include use of magnets to hold items on a refrigerator.) Ask: What happens as the magnet is brought near a refrigerator door? (It is pulled toward the door.) Explain that this pull is a force of attraction. Ask: What is a force? (a push or a pull) Point out that magnets exert forces on objects even when they aren t touching. That s because magnetic force acts even at a distance. MAGNETS AND ELECTROMAGNETISM SECTION 1 WHAT IS A MAGNET? 9 Student Resource 1.1 (p. 9) Testing for Magnetic Attraction STUDENT RESOURCE 1.2 ACTIVITY SHEET What Do Magnets Attract? 1 Read the list of materials in the table. Predict which materials the magnet will attract. Write Yes or No in the Prediction column. Metal Sample Prediction Attracted to Magnet? Test Result Attracted to Magnet? 20 minutes Pairs aluminum foil brass brad (copper and zinc) penny iron rivet magnetite rock silver steel nail steel paper clip 2 Test each material with the magnet. In the Test Result column, write Yes if the material is attracted to the magnet. Write No if the material is t attracted to the magnet. Conclusions Predictions may vary. 3 Which metals were attracted to the magnet? Iron and steel were attracted to the magnet. 4 What metals were t attracted to the magnet? Objectives Students predict what materials a magnet will attract and then test their predictions. Students identify materials that are attracted to a magnet. For the class 2 pc. aluminum foil 2 brass brads 16 index cards 2 pc. magnetite 2 paper clips 2 *pennies 16 plastic trays 2 rivets, iron aluminum, brass, copper-zinc, silver 10 MAGNETS AND ELECTROMAGNETISM SECTION 1 WHAT IS A MAGNET? Sec04pg009_011.indd 10 9/4/05 2:09:30 PM Student Resource 1.2 (p. 10) 4 EXPERIENCE SCIENCE 16 magnets, ferrite 1 *marker 2 nails 2 silver jewelry or other objects *Not provided in kit

2 What Do Magnets Attract? (continued) Student Resource 1.2 Testing for Magnetic Attraction Inquiry Focus Predict In Advance Place one sample of each material to be tested in a separate plastic tray. Make two trays for each item. Use an index card to label the type of metal found on each tray: aluminum foil: aluminum brass brad: brass iron: iron rivet magnetite rock nail: steel paper clip: steel penny: copper and zinc silver jewelry (or other object): silver Set up 16 stations around the room, each containing one tray. 1. Discuss what kinds of materials are attracted to magnets. Ask: What kinds of materials are attracted to magnets? (Students may say that metals are attracted to magnets. Accept all answers for w.) Tell students that they will conduct some experiments to find out. A Ferrite magnet Step 3: Never place magnets near audio or video tapes, diskettes, TVs, VCRs, computers, or other magnetic media. 2. Distribute the Student Resource and have students make predictions. Make copies of Student Resource 1.2, Testing for Magnetic Attraction, and distribute to students. Have students read the list of metals in the table and then fill out the Prediction column. 3. Prepare students to test materials. Provide each pair with a ferrite magnet. Tell students they will be moving around the room to test their predictions. Explain that they should test the metal at each station with the magnet. If the metal is attracted to (pulled toward) the magnet, they should write Yes in the Test Result column of the table. If the metal is t attracted to the magnet, they should write No. SECTION 1 WHAT IS A MAGNET? 5

3 What Do Magnets Attract? (continued) Step 4: You might explain that pennies today are made of copper and zinc. Neither is attracted by a magnet. Prior to 1982 pennies were made entirely of copper. 4. Discuss students observations. Ask: What metals did the magnet attract? (iron and steel) Remind students that only certain metals are magnetic, or attracted to a magnet. These include iron, cobalt, nickel, and steel. Point out that steel is a blend of materials that includes iron and carbon. Ask: Did the magnet attract the magnetite? () Why? (Magnetite is naturally magnetic.) Tell students that magnetite contains iron, a metal that is magnetic. Assessment Ask: Would a steel rod be attracted to the magnet? Why or why t? (Yes. Magnets attract materials made of steel.) Is Cereal Magnetic? 10 minutes Objectives Students observe that some cereals contain iron. Teacher Demonstration For the teacher * breakfast cereals (including Whole Grain Total ) 1 magnet, cow 1 *overhead projector 1 Petri dish *water *Not provided in kit Inquiry Focus Observe 6 EXPERIENCE SCIENCE

4 Is Cereal Magnetic? (continued) 1. Set up materials. Place a Petri dish on an overhead projector. Carefully fill the Petri dish with water. Cow magnet A Using a magnet to attract the iron in cereal Step 2: Tell students that ranchers use a device to insert a cow magnet into the first of a cow s four stomachs. The magnet attracts small pieces of wire that enter the cow s feed from bales of hay. When food eaten by the cow moves into the next stomach, the pieces of wire remain behind. 2. Students make observations. Break apart some of the pieces of cereal that are NOT Total and t high in iron. Float these pieces on the water in the Petri dish. Turn on the projector. Hold the cow magnet near a piece of the cereal without touching it. Tell students to observe the cereal as you move the magnet toward the edge of the Petri dish. (The cereal piece will t be pulled.) Now repeat with small pieces of the Whole Grain Total flakes. (The flake pieces are pulled by the magnet.) Turn off the projector. 3. Discuss students observations. Show students the Nutrition Facts label of the Total cereal box. Explain that this label tells buyers what nutrients are in the cereal and the amounts of these nutrients in one serving. Ask a volunteer to read aloud each of the nutrients listed. Ask: Which nutrient is attracted to a magnet? (iron) Explain that the cereal flakes contain iron, a nutrient needed by humans in their diet. Repeat the experiment using other cereals students brought in. Assessment Ask: Why were the flakes of cereal attracted to the magnet? (The iron in the cereal is attracted to the magnet; it is magnetic.) Extension Seeing Iron in Cereal Pour a cup of Total cereal flakes into a blender with two cups of milk. Holding one end of the cow magnet against the blender vessel, turn on the blender for 30 seconds. Tell students to closely observe the area of the blender nearest the magnet. (Black particles can be seen near where the magnet is located.) Remove the magnet quickly and have students observe what happens. (The black particles fall to the bottom of the blender.) Tell students that the black particles are pieces of iron that separated out of the cereal as it was blended. SECTION 1 WHAT IS A MAGNET? 7

5 Section Assessment Section 1 Assessment STUDENT RESOURCE 1.3 ASSESSMENT SHEET Vocabulary 1 What is a magnet? a material that attracts iron, steel, cobalt, and nickel Magnetic Attraction 2 A student uses a magnet to find out which nail is iron and which nail is aluminum. Which drawing shows the aluminum nail? Circle your answer. For each station 1 magnet, ferrite 1 plastic tray containing one aluminum foil, brass brad, iron rivet, and paper clip Student Resource 1.3 Section 1 Assessment Identifying Magnetic Test each material in the tray to see if it is attracted to the magnet. Write Yes next to each material the magnet attracts. Write No next to each material the magnet does t attract. 3 aluminum foil 4 brass brad 5 rivet 6 paper clip 7 Which objects contain iron, steel, cobalt, or nickel? rivet and paper clip MAGNETS AND ELECTROMAGNETISM SECTION 1 WHAT IS A MAGNET? Set up eugh materials stations around the room to allow one-third of the class to work alone at a station during the hands-on portion of the assessment. 2. Make copies of Student Resource 1.3, Section 1 Assessment, and distribute to students. 3. Divide the class into three groups. While one group is working at the stations to complete the hands-on portion of the assessment, the other two groups can be completing the top part of the assessment. Rotate the groups through the stations until each has completed the hands-on portion of the assessment. Student Resource 1.3 (p. 11) 4. Discuss the answers as a whole-class activity. 8 EXPERIENCE SCIENCE