CSI Literacy

Everything in the world is made of matter, and matter comes in three main states: solid, liquid, and gas. Solids, like a block of wood or an ice cube, have a fixed shape and a fixed volume. They don't change their shape easily. Liquids, such as water or juice, have a fixed volume but take the shape of their container. If you pour water from a tall glass into a wide bowl, the water spreads out to fill the bowl's shape. Gases, like the air we breathe, have no fixed shape or volume. A gas will spread out to fill any container it is in, no matter how big. Understanding these differences is the first step in classifying any substance you find.

When geologists study rocks, they look closely at the minerals inside them. Minerals have unique properties that help scientists identify them. One important property is hardness, which is tested by seeing if one mineral can scratch another. A diamond is the hardest mineral and can scratch almost anything. Another key property is luster, which describes how a mineral reflects light. Some minerals have a metallic luster, meaning they are shiny like a piece of metal. Others might have a glassy, pearly, or dull luster, meaning they are not very shiny at all. By observing a mineral's hardness and luster, a geologist can gather important clues about what kind of mineral it is.

Have you ever used a magnet to pick up paper clips? This works because paper clips are made of steel, a metal that is magnetic. Magnetic materials are attracted to magnets. Iron, nickel, and cobalt are the most common magnetic metals. However, it's a common mistake to think that all metals are magnetic. Many are not! For example, aluminum, which is used to make soda cans, is not magnetic. Copper, used in electrical wires, and gold, used in jewelry, are also not attracted to magnets. So, while many metals are magnetic, there are plenty of important metals that are non-magnetic. It all depends on the specific type of metal.

Why does a sponge soak up spilled water, but a raincoat keeps you dry? It's because they are made of different types of materials. A sponge is made of an absorbent material. Absorbent materials have tiny spaces or holes in them that trap water and hold it, like a paper towel or a cotton ball. On the other hand, a raincoat is made of a waterproof material. Waterproof materials do not let water pass through them. They form a barrier that repels the water, forcing it to roll right off. Plastic and rubber are common waterproof materials. Understanding whether a material is absorbent or waterproof is very important for choosing the right tool for a job, whether it's cleaning up a mess or staying dry in a storm.

Electricity needs a path to travel along, much like a car needs a road. Materials that allow electricity to pass through them easily are called conductors. Most metals, like copper and silver, are excellent conductors. That's why the inside of an electrical cord is made of thin copper wires. However, touching a conductor that has electricity flowing through it can be very dangerous. To keep us safe, wires are covered with materials called insulators. Insulators, such as plastic, rubber, and glass, do not allow electricity to pass through them easily. They block the flow of electricity. The plastic coating on a wire is an insulator that stops the electricity from leaving the wire and hurting you.

Why does a heavy log float in water while a tiny pebble sinks? It's all about density. Density is a measure of how much "stuff," or matter, is packed into a certain amount of space. Imagine two boxes of the same size. If you fill one with feathers and the other with rocks, the box of rocks will be much heavier. This is because rocks are more dense than feathers. In the same way, some materials are more or less dense than water. If an object is less dense than water, it will float. A wooden log has a lot of air pockets, making it less dense than water, so it floats. A small stone is very compact and has no air inside, making it more dense than water, so it sinks.