MOTHER NATURE'S MAGNET
Everyone has seen a magnet, but aside from decorating a refrigerator, what are its uses? Students will investigate the history of magnets and explore some of the ways that we use magnets.
To understand the uses of magnets in our everyday lives.
Students will be able to:
- List properties of magnets
- List at least 10 uses for magnets
- Identify classroom materials that are attracted to magnets
- Develop experiments to determine if an unknown sample of magnetite has the listed magnetic properties
Activity: 30 min.
- Bar magnet, Refrigerator magnet, Neodymium magnet, other various magnets
- Hand specimen of magnetite (lodestone)
- Various classroom materials: pencils with steel eraser holders, paper clips, paper, aluminum cans, steel cans, etc. (Allow students to develop a list of materials)
Over twenty-five hundred years ago, the Greeks discovered the first magnet. It was a naturally occurring rock with magnetic properties called lodestone, also known as magnetite. Magnetite is an iron ore whose molecules are aligned to give it magnetic properties. A thousand years later, the Chinese invented the first crude compass, composed of magnetic rock suspended on a string. When knowledge of this rock was brought to Europe in the fourteenth century, improvements were made and explorers like Magellan and Columbus were able to use it to navigate around the world.
When an object is magnetized and suspended from a string it becomes free to align itself with larger magnetic fields. Early compasses were constructed in this manner. The suspended object aligns itself with Earth's magnetic field and points north, helping navigators keep oriented.
Magnet molecules are all aligned in the same direction. The cooperative pull of each molecule causes a huge pull in that direction. When a magnet is exposed to metallic objects, it pulls on the metallic molecules and causes it to be attracted. This is why magnets will 'stick' to metals. Some metals will not be attracted by magnets. Their molecular properties do not facilitate the magnetic or molecular pull.
Besides refrigerator and compass magnets, magnets have an extraordinarily large number of uses including: holding objects, moving objects, suspending objects, making electricity, jewelry, medicinal purposes, navigation equipment, inspiration for bad poetry, and maintaining the digestive health of a cow, just to name a few. (Cow magnets are sold in ranch stores and fed to cows. The magnet sits in the stomach of the cow and attaches itself to any bits of metal the cow might ingest, holding it there so it doesn't injure the cow further).
- Hold up a magnet in front of the class. Ask students to identify the object that is in your hand. Pass out several types of magnets to small groups of students and have them identify what each group was given.
- Ask each group how they knew that it was a magnet. On a piece of paper, or in their science journal, have them describe the properties of magnets, and brainstorm a list of uses that we have for magnets.
- After the students have had time to make their lists, make two class lists up on the board, one for magnetic properties and another for uses. Go around the room and ask each group to contribute one property or use to the class list, until the students feel their list is complete.
- Once they have finished making their list, ask each group to determine which normal classroom materials are attracted to their magnets. Provide a box of several types of things that are attracted and some that are not attracted. Have the students keep a list of what is attracted.
- Once the students have finished experimenting with what is and is not attracted by magnets, make two class lists on the board. Each group contributes one thing that is or is not attracted to a magnet until the students feel their list is complete.
- Ask the students what is common with all of the materials that are attracted to the magnets.
- Hold up the hand specimen of the magnetite, and ask the students to identify the object in your hand.
Most likely they will say a rock or a stone.
- Ask the students how they know what it is, or what they would do to find out what this rock is. Have the students devise a plan, using the properties we just discovered relating to magnets, to determine if this rock is magnetic.
- Once the students have made their decision, make another class list on the board describing the properties of this rock.
- Explain that this rock is called magnetite. It is formed in nature and was found by the ancient Greeks to have the same properties that you just listed. They found that large pieces of it almost always pointed north when it was allowed just to hang or if it was floated on water. (Our specimens are too small). Because it always pointed north, they called it the "leading stone" which was shortened to "lodestone", another common name of this rock.
How could we use this stone? What are other historic uses of magnets? Who invented the compass? What is a compass? How do we use a compass? What could we do to turn this stone into a compass? Why do big pieces of this stone and other compasses point north?
Challenge students to a magnetic scavenger hunt. Now that they have the skills to test if an object is a magnet, have them spend a day of homework listing as many uses of magnets as they can find. Create a class list and post it.
Included National Parks and other sites:
Utah Science Core:
Kindergarten Standard 4 Objective 1,2,3
5th Grade Standard 3 Objective 1,2