Grade 2 Hands on Science Forces and Magnets

Transcription

1 Grade 2 Hands on Science Forces and Magnets Objectives: to discuss and demonstrate "what is a force?" and to demonstrate the "push and pull" forces produced by a magnet. Safety: Remind students of general lab safety (no running in the lab, listen carefully to instructions before touching materials, never eat or drink anything in the lab etc). Discuss how to safely use magnets - Refer to orange Safety sheet. Magnets are a lot of fun but can be very dangerous if ingested. Magnets can also be very damaging to electronic items. They can permanently erase the data stored in these items (including your cell phone). Always keep magnets away from electronics. Part A. Forces Ask "What is a force?" (a force is a push or a pull on an object that causes an object to move). a push will repel (force apart) two objects a pull will attract (bring together) two objects Have the students stand up and make their chair go towards the table. Ask "What was that force used?" (push - the chair was pushed towards the table) Have the students pull the chair away from the table and sit down. Ask "What was that force used?" (pull - the chair was pulled towards the student and away from the table) Chose one student to go and open a drawer. Ask: "What force did the student use to open the drawer?" (The force used was a pull.) Have the student close the drawer. Ask "What force did the student use to close the drawer?" (The force used was a push). Ask: "What forces do we use every day?" (push and pull) Part B: Showing PUSH/PULL with magnets. You will be provided with: 2 bar magnets A magnet is any object that produces a magnetic field - an invisible force that can attract (bring together) two objects or repel (push apart) two objects. A magnet has two poles: a north pole and a south pole. The magnetic force is always strongest around these poles. Like the saying "opposites attract", a magnet's north pole will be attracted to the south pole of another magnet and vice versa.

2 A magnet's north pole will be repelled by the north pole of another magnet's north pole and a magnet's south pole will be repelled by the south pole of another magnets south pole. The attract/repel forces shown by a magnet are due to the magnetic field produced at the poles of the magnet. Have each student to show the forces of pull/attract and push/repel using the bar magnets. Part C: Magnetic fields You will be provided with: a container with iron filings, bar magnets A magnet creates an invisible force field around it called a magnetic field: an area of invisible force that can pull/attract (bring together) two objects or push/repel (push apart) two objects. Though magnetic fields are invisible you can visualize their effect. Metals like iron, steel or nickel are attracted to a magnet. Iron filings, very small pieces of iron can be used to visualize the magnetic field of a magnet. Have the students take turns doing each step of these activities. Place a magnet down on the table. Place a plastic container of iron filings over the magnet. Observe what is happening to the iron filings. If time allows, repeat the above experiment with two magnets showing attraction and repulsion.

3 The pattern of iron filings shows the presence of the magnetic field produced by the magnet. The magnetic field is the strongest around the poles of the magnet as is shown by the higher concentration of iron filings near the poles as compared to the center. Part D: What do magnets attract? What you will be provided with: penny, nickel/dime, piece of wood, chalk, rubber band, paper clips, magnets Read the magnet poem to the students: Magnets (Author Unknown) I am a mighty magnet, I can be very strong. But if you use me exactly right Nothing can go wrong. I can pick up many objects But not everything you see, I only pick up objects That are attracted to me. So take me now and try me out And you will quickly see, What different kind of things Are pushed and pulled by me. Like the iron filings in the previous activity, other items can also be attracted to magnets.

4 Have the students predict which of the items (penny, nickel/dime, piece of wood, chalk, rubber band, paper clips) will be attracted to the magnet. Have the students complete part D1 on their worksheet. Using the large magnet with the handle, have the students test to see which of the above items are attracted to (will stick to) the magnet. Have the students complete part D2 on their worksheet. Ask "Did all of the items stick to the magnet? If not, which ones did?" (No, only the metal items (paper clips) will stick to the magnets Ask "Why?" Only the paper clips contained iron, steel or nickel that would make them attracted to the magnet. Pennies are made of zinc and copper which are not attracted to magnets. Nickels, dimes and quarters are mostly copper and though they contain nickel it is too small of an amount to allow the coin to be attracted to the magnet. Park E: Strong or weak magnets. What you will be provided with: "fishing rods" with different magnets, paper clips Some magnets have strong magnetic fields or attractive forces around them. These are called strong magnets. Some magnets don't have as much force or have weak magnetic fields and are called weak magnets. These different magnets will be more or less attracted to metal objects, respectively. This activity will be completed together as a table. The total number of paper clips will be counted and totaled per table. The data will be used to make a bar graph in the student's handout. The students will use the different "fishing rods" with strong or weak magnets to see which of the magnets can pick up the greatest number of paper clip "fish". Ask: "Which of the magnets picked up the most paper clip "fish"? Why? (The magnet that picked up the most "fish" was the strongest magnet and the magnet that picked up the least fish was the weakest magnet.) Part F: Will the force of a magnet (magnetic field) go through different items? What you will be provided with: a bar magnet with a handle, paper clips, cloth, waxed paper, paper, aluminum foil The attractive force of a magnet or it's magnetic field extends a distance around the magnet. This force can extend through various materials.

5 Ask: "Do you think a magnetic force/magnetic field can go through things?"(yes) Determine if a magnet can attract paper clips through different materials such as cloth, waxes paper, paper or aluminum foil. Try testing the ability of the magnetic field to attract paper clips through the material with the magnet close or touching the material. Then move the magnet 2 inches away and see if there is a difference. Ask: "What material can the magnetic field pass through?"it should pass through all of the materials. Iron and steel work well as a shield to a magnetic field, but only if they are thick enough.) Ask: "What is your conclusion?" (The magnetic field is able to pass through all of the materials tested and extends a small distance from the magnet). Review questions to ask: Push and pull are types of (forces). Shutting a cabinet door is an example of the force (push). Opening a drawer is an example of the force (pull). Magnets have two forces called (repel/push and attract/push). The force of push on a magnet is called (repel). The force of pull on a magnet is called (attract). The area around a magnet which has a force is called a (magnetic field). What are the names of the two poles of a magnet? (north and south pole) Does the north pole repel or attract the north pole of another magnet? (repel) Does the north pole repel or attract the south pole of another magnet? (attract) Fun interesting facts about magnets: A magnet can be made from a steel object by striking it with a magnet. Once magnetized, a piece of steel can remain magnetized indefinitely. A magnetic compass works because the earth itself is a magnet (with a north and south pole). The compass magnet interacts with the earth magnet. The magnetic field of the earths magnet extends into space and results in the northern and southern lights (Aurora Borealis/Aurora Australis). The earths magnetic field repels large amounts of solar radiation from the sun. Life on earth would end if there was no magnetic field as the radiation levels would be too high. The magnetic field of the earth is actually weaker than the magnet field produced by the magnets on your refrigerator. The Sun has a magnetic field but the moon does not. Why? (The sun is made up of molten metals, while the moon is made of non-metallic materials). The first compass was made is 1200 BC. If a magnet is broken, each piece becomes another complete magnet with the correct, complementary pole forming at each of the broken ends.