matter - physical material of the universe  

• different compositions due to different arrangements of elements
• atoms - smallest building blocks of matter
• properties of matter change due to composition/structure of the atoms
• molecule - 2+ atoms joined in a specific shape

states of matter - gas, liquid, or solid  

• gas - aka vapor, has no definite shape/volume; molecules move at high speeds, often colliding w/ each other
• liquid - definite volume, but no definite shape; molecules can slide over each other
• solid - definite shape/volume, molecules held tightly together

pure substances - has distinct properties and doesn't vary from sample to sample  

• either elements or compounds
• elements - cannot be decomposed into simpler substances
  • oxygen, silicon, aluminum, iron, calcium make up most of crust
  • oxygen, carbon, hydrogen makes up most of human body
  • similar elements grouped in the same column on the periodic table
• compounds - combination of 2+ elements
  • law of constant composition (definite proportions) - composition of a pure compound is always proportionally the same
• mixture - combination of 2+ substances; each substance keeps its characteristics
  • components - substances making up a mixture
  • homogeneous mixture (solution) - same throughout
  • heterogeneous mixture - not the same composition throughout

properties of matter - can be physical or chemical  

• physical changes - can be measured w/o changing the composition of the substance (ex. odor, color, density, melting point, boiling point, hardness)
• chemical properties - describes how the substance reacts w/ other substacnes (ex. flammability)
• intensive property - doesn't depend on amount of substance available
• extensive property - depends on the amount of substance available
• physical change - substance retains composition but changes appearance
• chemical change - substance changes to a chemically different substance

separation of mixtures - possible by using the components' different properties  

• filtration - uses a filter to separate a mixture (usually water-solid mixture)
• substances w/ lower boiling points are more volatile
• distillation - boiling a solution to isolate the more volatile substance
• chromatography - "writing of colors"; depends on ability of substances to adhere to surfaces of various solids

scientific method - guidelines for the practice of science  

• starts w/ data collection
• hypothesis - temporary explanation for something; can be disproved
• scientific law - verbal/mathematical statement that summarizes lots of observations
• theory - general hypothesis that can consistently predict results