Changes to state of matter • A substance changes state when its thermal energy increases or decreases significantly. • Three frequently observed changes to states of matter are melting, freezing, and vaporization.
Melting • Melting is the change in state from a solid to a liquid. • Most pure substances begin to melt when they reach their “melting point” which is the temperature which they turn into liquid. • When a substance melts the particles vibrate so fast they break free of their fixed position of the solid. • Substances usually melt by taking in heat from the environment.
Freezing • Freezing is the change from a liquid into a solid. • The reverse of melting. • When a substance begins to freeze they begin to take on fixed positions to form a solid rather than vibrate more freely in a liquid. • When the temperature of the liquid begins to drop down to the point where it begins to form a solid the liquid has reached its “freezing point” or the temperature that is required for it to freeze. • The freezing point of water is 0 C, or 32 F.
Vaporization • The change in state from a liquid to a gas. • Vaporization occurs when a liquid gains enough energy to move independently enough to form a gas. • When vaporization is occurring on the surface of a liquid it is called evaporation. • Boiling point- the specific temperature a pure substance begins to boil. • Example- Water boils at 100 C, or 212 F at sea level.
Condensation • The opposite of vaporization is condensation. • During condensation particles lose enough thermal energy to form a liquid. • A cloud is water in a vapor form that has condensed into the liquid and forms shape of a cloud in the sky.
Sublimation • Sublimation occurs when surface particles gain enough energy to become a gas. • During sublimation particles do not transition from a solid into a liquid, instead they move directly from a solid state into a gas state. • Example: dry ice moves directly from a solid to a gas at room temperature
Interactive demonstration of ice cube being heated and particles move faster and faster until it melts and vaporizes. http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks3/science/changing_matter/changingmatter.swf Water cycle- solid, liquid, gas- evaporate, melt, freeze http://www.bbc.co.uk/schools/scienceclips/ages/9_10/changing_state_fs.shtml http://www.youtube.com/watch?v=3SUPA2CBjGs Bill Nye: States of Matter