| A | B |
|---|
| molecule | a unit formed of 2 or more atoms |
| molecules form when... | electrons in 2 or more atoms are attracted to the nuclei of both or all of the atoms, NOT just to a single nucleus |
| 3 states of matter | solids, liquids, gas |
| solids | this state of matter has a definite shape and definite volume-- molecules are held tightly together |
| liquids | definite volume, no definite shape--molecules move freely |
| gas | NO definite volume or shape--molecules are far apart |
| gas can be compressed easily because... | the large space between molecules |
| Heat energy | this form of energy is usually the cause of a change of state |
| a solid changes to a liquid when... | you add heat to a solid |
| liquid becomes a gas when... | you add heat to a liquid |
| Liquid becomes a solid when... | you take away heat from a liquid |
| Gas becomes a liquid when... | you take away heat from gas. |
| melting point | the tempature at which a substance changes from a solid to a liquid |
| boiling point | the tempature at which a substance changes from a liquid to a gas |
| substances with a strong attraction between their particles have... | high melting and boiling points |
| substances with weak attraction between their particles have... | low melting and boiling points |
| sublimation | when a substance changes states directly from a solid to a gas |
| pressure | this besides heat can cause a change of state |
| evaporation | vaporization that takes place on the surface of a liquid |
| vaporization | when the particles in a liquid gain enough energy to form a gas |
| condensation | when particle lose thermal energy and form a liquid |
| sublimation | particles go from a solid to a gas (dry ice) |
| freezing | loss of energy makes the particle form a regular pattern and become solid |
