90 Mixing Matter-Mid

Mixing Matter Written by David Dreier

Introduction Look at the things around you. Maybe you see books and a desk. What are they made of? The books are probably made of paper. The desk could be made of materials such as wood, glass, metal, or plastic. Maybe it's made of several materials put together. All these objects and materials are types of matter. Everything that takes up space and has weight is made of matter. But what is matter? This book explores the types of matter, how those materials can be mixed to make new things, and how matter can change.

Elements All matter is made of simple materials called elements. An element is a substance that cannot be broken down into other substances. Imagine cutting a piece of gold into smaller and smaller pieces. No matter how small you make the pieces, each one will still be gold. That is why gold is an element. Word Wise Some symbols for elements come from the Latin language. For example, Fe is the symbol for iron. Fe is short for ferrum, the Latin word for iron.

There are about 120 elements. Some are metals, such as iron and gold. Others are usually gases, such as oxygen and helium. Each element has a symbol. The symbol is one or two letters that are often short for the element's name. For example, oxygen is "O" and helium is "He." Elements combine in different ways to make materials that we see and use every day.

Atoms Imagine that you could look deep inside any object. You would see that everything is made of tiny particles called atoms. Atoms are so small that they can only be seen with strong microscopes. Every element is made of a certain kind of atom. And no two elements have atoms that are the same. The smallest piece of gold is a gold atom. If you could look even deeper inside an atom, you'd see that it is made of even smaller particles. An atom is a little like the solar system. In the solar system, planets circle the Sun. In an atom particles called electrons circle the center of the atom, The center of the atom. is called the nucleus Particles called protons and neutrons. are found in the nucleus.

All atoms of the same element have the same number of protons and electrons. (The number of neutrons sometimes changes.) But atoms of different elements contain different numbers of protons and electrons. Even though particles are far too tiny to see, they still weigh something. The more protons and neutrons an atom has, the more it will weigh. Helium atoms have just 2 protons and 2 neutrons in their nucleus. But lead has 82 protons and 125 neutrons. So lead is much heavier than helium.