Science - 5th Grade
Standard 3 Objective 1
Science - 5th Grade
Standard 3 Objective 2
2 class periods of 60 minutes each
Magnets are attracted to certain metals and other magnets. Students feel the attractive and repulsive forces of magnets. Students can observe a magnetic force field by lining iron filings up with magnets. The north and south poles of a magnet can be determined by comparing them to the Earth's magnetic field. Magnetizing a needle and floating it on water makes a floating needle compass.
A magnet is a metal object that is able to pull or attract certain other metals. This pull or attraction is a force called magnetism. Weak magnets naturally occur in nature; the mineral lodestone or magnetite (a magnetic oxide of iron) was the first magnet used around 800 BC. Stronger magnets used today in electronic devices or in other ways are manmade.
Magnets exist because when the electron spins in an object are all aligned in the same direction the material is magnetized. Normally, these electron spins are not aligned and the magnetic field is scattered. When the minor magnetic fields are scattered, no magnetic field is generated because the small magnetic fields cancel out. Therefore, in a magnet when the poles line up with the north poles facing one end of an object and the south poles facing the other end. This arrangement creates a magnet. The more domains pointing in the same direction creates a stronger magnet.
Attraction is the pull force a magnet has for another object. You can't see this force - but you can feel it. This object a magnet is attracted to may be a metal or another magnet's opposite pole. When a magnet gets near a metal it is attracted to, the electrons in the metal are realigned and their small magnetic domains line up to be attracted to the magnet. This attraction is temporary. After the magnet is removed from the metal the objects will randomly scatter their magnet poles back to where they were before they were attracted to the magnet. A magnets strongest area of attraction is at the poles.
Repulsion is the pushing away force a magnet has for another magnet lined up in the same direction. These attractive and repulsive forces create a magnetic force field around every magnet. These force fields are invisible but can be seen by placing magnets near iron filings. The iron filings will line up along the magnetic force field.
1d. Compare things, processes, and events.
1h. Predict results of investigations based on prior data.
3a. Know and explain science information specified for the grade level.
4b. Describe or explain observations carefully and report with pictures, sentences, and models.
4c. Use scientific language in oral and written communication.
Pre-lab discussion: Ask the students about their previous knowledge of magnets. Show them a strong pair of magnets so that you can demonstrate the attraction and repulsion of the magnets. Discuss uses for magnets in their everyday lives. How many magnets do they think are in the room? (iPods, computers, monitors, televisions, cell phones, etc) Diagram and explain the notes given in the background information section.
Experiment 1: Magnet Properties
Experiment 2: Finding the North and South Poles of a Magnet
Experiment 3: Magnetic Fields of Permanent Magnets
A magnetic field is the area in which a magnetic force is present. We can't see magnetic fields, but we can show their pattern by scattering iron filings in the magnetic field. The iron filings then become magnetized and line up with the magnetic field of the magnets.
Gently tap the petri dish until the iron filings form a pattern. Discuss the pattern created by the magnetic field.
** Be careful that the iron filings do not get on the magnets.
Notice that when the two magnets attract each other, the iron filings can be found in the space between the two magnets. When the two magnets repel each other; the iron filings are repelled from the space between the magnets.
Experiment 4: Making a floating compass - Sailors used Floating compasses as early as the thirteenth century. The sailors used the floating needle to find north during cloudy weather when they couldn't see the stars.
This temporary needle magnet or any magnet is stronger than the earth's magnet at short distances. This is observed when the second needle can override the magnetic field of the earth and disrupt the compass. But the earth's magnetic field is much farther reaching since it goes from the center of our earth all the way to our petri dish needle while our two needles only react with each other over a very short distance.
Rio Tinto Hands-on Science Curriculum Team