Magnetism
Magnetism is the force that makes magnets pull iron objects toward them or push other magnets away.
Two fridge magnets on a kitchen counter show how magnetism works. Slide them close and they snap together or push apart. That force reaches through the air between them. A fridge magnet uses that same pull to hold a note to the steel door.
Explaining magnetism by grade level
Hold a magnet near a paper clip. The clip jumps to the magnet and sticks. Try it with a penny and nothing happens. Magnets only pull on certain metals like iron and steel.
Projects that explore magnetism
Magnetism can push other magnets away. When two north poles face each other, they push apart with enough force to float a foam-core platform above a wooden track lined with magnetic strips. The platform hovers about a quarter inch up and glides from one end to the other when given a gentle push.
Magnetism pulls iron objects toward a magnet. Tiny steel fibers made from extra-fine steel wool respond the same way. You mix the fibers into baby oil inside a plastic bottle and hold a magnet near one side. The fibers align themselves, making the invisible pulling force visible.
Magnets attract paper clips through cardboard and air. But some materials stop that pull completely. You build a cardboard sandwich with a magnet on top and paper clips hanging from the bottom. Slide a popsicle stick into the gap and the clips hold. Slide in a metal strap and the clips fall. Only magnetic materials absorb field lines and act as shields.
The force that makes magnets pull iron objects toward them can weaken with heat. Permanent magnets lose pulling power as their temperature rises. You test five magnets at temperatures from 0°C to 100°C by pressing each one into a tray of steel washers and counting how many stick. At 0°C the magnets grab around 30 washers. At 100°C they pick up fewer than 10.