Meteorites and magnets
Most meteorites contain iron metal, so most of them are attracted to a magnet. This lesson shows how a magnet helps scientists, and why it cannot give the whole answer on its own.
- Name materials that are attracted to a magnet.
- Explain why most meteorites are attracted to a magnet.
- Explain why a magnet test alone cannot prove a rock is a meteorite.
Links to: Year 3 science, forces and magnets: magnetic materials and grouping materials by whether they are attracted to a magnet; working scientifically: setting up a simple test.
Magnetic materials
A magnet attracts only a few materials. The most important are iron, nickel and cobalt, and steel, which is mostly iron. Wood, plastic, glass, paper, aluminium, copper and gold are not attracted at all.
You can group objects by testing them: bring a magnet close and see whether it pulls.
Why meteorites stick
Iron meteorites are almost all iron and nickel, so a magnet grips them strongly. Most stony meteorites, the chondrites, also contain small grains of iron-nickel metal mixed through the rock. That is enough for a strong magnet to be attracted to them too.
So a magnet is the first test meteorite hunters use. If a rock is not attracted to a magnet at all, it is very unlikely to be a meteorite. A few kinds, such as most meteorites from the Moon, Mars and the asteroid Vesta, have almost no metal, so a magnet hardly pulls on them at all.
Why a magnet is not enough
Plenty of Earth rocks are attracted to a magnet too. The mineral magnetite, iron ore and slag, which is waste left over from making iron, all stick to a magnet. These are the most common rocks that people mistake for meteorites. Scientists call them meteorwrongs.
A magnet can say that a rock might be a meteorite, but more tests are needed. You will meet those tests in the next lesson.
Reading a results table
A class tested 20 rocks with a magnet. 12 were attracted and 8 were not. Two of the attracted rocks were later confirmed as meteorites. What fraction of the attracted rocks were meteorites?
- The attracted rocks are the group we are looking at, so the bottom number of the fraction is 12.
- The meteorites in that group are the top number: 2.
- The fraction is 2/12. Both numbers divide by 2, so it simplifies to 1/6.
Answer: 1/6 of the attracted rocks were meteorites, which shows that most rocks a magnet picks out are not.
Collect ten safe objects from the classroom, such as a paper clip, a coin, a pencil, a spoon, a plastic ruler and a piece of foil. Predict which ones a magnet will attract, then test them and record the results in a table with columns for the object, your prediction and the result. Which predictions were wrong?
Quiz
5 questions. Choose an answer to see whether you are right and why. Finish the quiz to complete the lesson.
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Question 1Which of these materials is attracted to a magnet?
Iron, nickel and cobalt, and steel made from iron, are attracted to magnets. Plastic, wood and glass are not.
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Question 2Why are most stony meteorites attracted to a magnet?
Chondrites have specks of iron-nickel metal mixed through the rock, and a strong magnet is attracted to them.
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Question 3What is a meteorwrong?
Meteorwrongs are ordinary Earth materials, such as slag or magnetite, that look a bit like meteorites.
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Question 4A rock is attracted to a magnet. What can you say?
Many Earth rocks, such as magnetite and slag, are attracted to magnets too, so a magnet alone cannot prove anything.
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Question 5Which of these is NOT attracted to a magnet?
Aluminium is a metal, but it is not magnetic. Steel and iron are.