This chapter begins the first where we will look at matter on a microscopic scale. Matter is made of small particles of atoms or molecules. There are three common states of matter, solid, liquid and gas. A gas and a liquid will change shape to fit the shape of their container. A gas will change volume to fit the volume of the container.
| |
Definite shape | definite volume |
| solid | yes | yes |
| liquid | no | yes |
| gas | no | no |
In general, solids are denser than liquids, which are denser than gases. . The particles in the solid are touching with very little space between them. The particles in a liquid usually are still touching but there are some spaces between them. The gas particles have big distances between them.
Solid – In a solid, the attractive forces keep the particles together tightly enough so that the particles do not move past each other. Their vibration is related to their kinetic energy. In the solid the particles vibrate in place.
Liquid – In a liquid, particles will flow or glide over one another, but stay toward the bottom of the container. The attractive forces between particles are strong enough to hold a specific volume but not strong enough to keep the molecules sliding over each other.
Gas – In a gas, particles are in continual straight-line motion. The kinetic energy of the molecule is greater than the attractive force between them, thus they are much farther apart and move freely of each other. In most cases, there are essentially no attractive forces between particles. This means that a gas has nothing to hold a specific shape or volume.
(A fourth state of matter, called plasma, exists when a gas becomes ionized. Plasma exists inside stars and in interstellar gases.)
Your book has an interesting animation on this subject and I urge you to view it. ( The States of Matter)