Pre-Chem Studying

-physical material of the universe
-anything that has mass and occupies space
100 or so elementary substances
-building blocks of matter
-smallest particles of an element to retain its identity
states of matter
pure substance
-matter that has distinct properties and a composition that does not vary from sample to sample
-ex: water and salt
-substances composed of 2 or more elements
-contains 2+ kinds of atoms
-combinations of 2+ substances where each substance retains its own unique identity
-can be separated
law of constant composition
elemental composition of a pure compound is always the same
homogeneous mixtures
physical changes
-changes appearance but not composition
-ex: evaporation of water
-incl all changes of state
chemical changes
-aka chemical rxns
-substance is transformed in to chemically different substance
-ex: when hydrogen burns in the air
-measure of the amount of material in an object
-base unit is the kilogram
how closely individual measurements agree with one another
how closely individual measurements agree with the correct or “true” value
law of conservation of mass
-or matter
-atoms are neither created nor changed during chemical rxns
-total mass of materials present after a chemical rxn is the same as before
-extremely small dense region at the center of at atom
-most of the mass of an atom
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