SOLIDS Particles in solids are "locked" in place.  Particles in solids do move, but only shake a little bit back and forth.  That's why solids keep their shape and size.  Particles in solids are held together by forces called bonds.  If the bonds are strong, then so is the solid.  For example, the bonds in table salt are very strong, and it takes 801°C to melt table salt.  It takes 100°C to melt ice into water. Many solids have their particles arranged in certain ways all the time.  We call these things crystals.  If you could see microspocic things, you would see that every piece of table salt is shaped like a little cube.  This happens because of the way the particles get together when the slat originally forms.  Here is a microscopic picture of some table salt:

LIQUIDS If a solid absorbs enough heat, the particles can speed up enough to break the bonds that had been holding them in place.   This frees the particles up enough to slide around past each other.  We call this the liquid state.  The particles still attract each other, but not enough to form a crystal.  Liquids can be poured from one container to another, and they take the shape of that container.  Here is a picture of some iron that has been heated enough to melt:

GASES If enough energy is added, particles can get free from solids or liquids and fly out into the air.  The particles of gases do not attract each other much at all.  They are free to zip around and bounce off things.  When you boil water, you are turning it into a gas.  The bubbles are made of gaseous water (which is invisible), and rush to the top of the container because gases are less dense.  Here is a picture of gaseous water vapor bubbles rising in a glass of boiling water:

CONSTRUCTED RESPONSE ITEMS
Describe the particles in a gas, and the changes they would go through if they first became liquid, and then part of a solid crystal.