Substraction
On substraction i got correct 8/14


Have you ever tried to skip rock across water? did it skip over the water and then sink? most rocks sink in water. look at this picture. this rock is floating. do you know why it can float? rocks can be used in many ways. you decide how a rock can be used by it's properties. some rocks make good building materials. rocks can be very strong. strong rock wear away slowly. usually rocks do not burn or rust. they do not get wet inside. all of these properties help to make many rocks useful as building materials. have you ever used a compass? like a compass, the rock shown at the right can help you find direction. it has a property that most rocks do not have. when it is held by a string it will turn and point north.

Lodestone (magnetite)
The rock is called lodestone, a naturally magnetized form of magnetite (an iron oxide).
It has a magnetic property most rocks do not have — it can attract iron.
When hung from a string, it aligns with Earth’s magnetic field and points toward the north–south direction.
Long ago people used lodestones as the first compasses to find direction.
Quick test: bring a small piece of iron (a pin) close to the rock — if the pin is attracted, the rock is magnetic.