C HANGES OF STATE Chemistry Standard 7c

W HAT IS A CHEMICAL CHANGE ? Two or more substances react and make something completely different Example: Something burns rusting Explosive sodium and poisonous chlorine make table salt (Na + Cl  NaCl)

W HY IS SALT SO STABLE ? When salt is made, it forms a lattice, or a strong cube structure. Positive Sodium is attracted to negative Chlorine

W HAT IS A P HYSICAL C HANGE ? Change in size, shape, amount, state but NOT a change in substance! Examples: ice melting Cutting an apple in half Pouring Mt. Dew into a glass Melting point Boiling point

Description of Phase Change Term for Phase Change Heat Movement During Phase Change Solid to liquidMelting Heat goes into the solid as it melts. Liquid to solidFreezing Heat leaves the liquid as it freezes. Liquid to gas Vaporization, which includes boiling and evaporation Heat goes into the liquid as it vaporizes. Gas to liquidCondensation Heat leaves the gas as it condenses. Solid to gasSublimation Heat goes into the solid as it sublimates.

I MPORTANT VOCABULARY Boiling point: temperature at which a liquid turns into a gas (Endothermic) Freezing Point: temperature at which a liquid turns into a solid (exothermic) Melting Point: temperature at which a solid turns into a liquid (endothermic) Condensation: process of gas becoming liquid Vaporization: process of liquid becoming gas Sublimation: process of a solid turning into a gas

Watch water go through phase changes! Here Here Endothermic (heating up) Exothermic (cooling down)