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