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ESCI 215
Chapter 6
Magnetite
 Magnetism was discovered more than 3000 years ago
 Certain rocks (magnetite) attracted bits of iron
 Magnetite formed from the slow hardening of the
earth’s crust
 The earth’s magnetic field made it magnetic
 Magnetite was used by sailors in 1200 BC to point the
way north
 This allowed them to always know which way they were
going regardless of weather, day/night, etc.
What Causes Magnetism?
 Substances are made up of atoms
 Atoms can have a positive or negative charge
 In non-magnetic substances (i.e. paper, wood, plastic), the
atoms group together in opposite charges (positivenegative) and cancel each other out
 In magnetic substances, atoms group themselves into small
regions – magnetic domains – an arrange themselves
randomly
 When a magnet is brought near, the domains line up and the
substance is attracted to the magnet
 On magnets, the positive end is called North and the
negative end is called South
 On the Earth, the North pole has a negative charge and the
south pole has a positive charge
What do Magnets Attract?
 Non-metallic objects are not attracted
 Not all metallic objects are attracted
 Only iron, nickel, cobalt are attracted
 Some combinations of metals are attracted
 Iron, aluminum, nickel, cobalt mixed together

Aluminum on its own is not magnetic
(Events 6-A and 6-B)
Magnetism is a Force
 Magnetism is a force
 Magnets have a magnetic field and it is a force that
attracts magnetic substances


Event 6-C shows how iron filings will line up along this force
Unlike poles are attracted (N and S) and like poles are repelled
 This magnetic field acts through certain materials (i.e.
paper, glass, copper, wood, aluminum foil) and is
blocked by others (i.e. iron, steel)


Any material that is magnetic will block the line of force
Event 6-D
Temporary and Permanent
Magnets
 Temporary magnets (Electromagnets)
 The magnetic force can be turned on and off using an
electric current
 Permanent magnets
 Stay magnetic for long periods of time if handled
carefully
 Lose magnetism by:



Placing it in a powerful external magnetic field
Heating it too much
Hitting or dropping it
How to Make a Permanent Magnet
 Materials:
 Hard steel (i.e. hacksaw blade, sewing needle, darning
needle, workshop file)
 Magnet
 Methods:
 Hold the hard steel and stroke it 20 – 30 times with a
magnet
How to Make a Compass
 Materials:
 Magnetized needle
 Cork
 Plastic or glass container
 Water or oil
 Methods:
 Fill the container with the liquid, put the slice of cork in
the liquid and put the needle on the cork
 Observe the direction the needle moves to (N)
Assessment and Instruction
 Students could make a compass and write a summary
how it works and how they know which end points
north
 What can the students say about the poles of the
needle? Do they use vocabulary such as magnetic
poles, domains, magnetic field?
Check website listed on page 101
Discussion
 Where does this topic fit into the Science curriculum?
 Which grades and strands?
 Which curriculum objectives relate to the discrepant
events?