Copyright © 2007 Dorling Kindersley
Everything you can hold, taste, or smell is made of matter. Matter makes up everything you can see, including clothes, water, food, plants, and animals. It even makes up some things you cannot see, such as air or the smell of perfume. You can describe a type of matter by its MATERIAL PROPERTIES such as its colour or how hard it is. Matter is made up of PARTICLES so tiny that only the most powerful microscope can see them.
Not everything is made of matter. Non-matter includes the light from a torch, the heat from a fire, and the sound of a police siren. You cannot hold, taste, or smell these things. They are not types of matter, but forms of energy. Everything that exists can be classed as either a type of matter or a form of energy.
Different types of matter have different material properties that make them useful for different jobs. A plastic hosepipe is flexible, so it can be pointed in any direction. A perspex visor is transparent, so the wearer can see straight through it. A firefighter’s suit is shiny so it can reflect heat and light. Flexibility, transparency, and shininess are three examples of material properties.
All matter is made of incredibly tiny particles called atoms. Atoms are far too small to see with our eyes, but scientists have worked out how small they are. There are many kinds of atom. Sand grains are made of two kinds of atom: oxygen and silicon. People are made of about 28 different kinds of atom. Material properties depend on the kinds of atom the material is made from.
Grains of sand look like pieces of gravel when viewed through a microscope. They have different shapes and sizes. Each grain contains millions of atoms, too small to see with a microscope. A sand grain the size of the full stop at the end of this sentence would contain about 10 million million million atoms.
We cannot really see atoms with microscopes. The best we can do is image them, by bouncing light off the particles. A computer translates the light beams into an image. Scanning tunnelling microscopes (STM) and atomic force microscopes (AFM) do this.
Democritus was one of the first philosophers (thinkers) to say that everything was made up of particles too small to be seen. He believed these particles could not be destroyed or split. Democritus said that all changes in the world could be explained as changes in the way particles are packed together.