| 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 |
| polymers | very large molecules that can contain hundreds or thousands of atoms |
| 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 |
| plasma | a gas in which some of the electrons have been removed from the atoms or molecules so that the substance has free negatively charged electrons and positively charged ions |
| examples of natural Plasma | stars, lightning, the northern lights and inner core of flames |
| examples of man-made Plasma | flourescent lights, neon signs, vaor lamps, and computer chips |
