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-physical material of the universe
-anything that has mass and occupies space |
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| 100 or so elementary substances |
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-building blocks of matter
-smallest particles of an element to retain its identity |
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-matter that has distinct properties and a composition that does not vary from sample to sample
-ex: water and salt |
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-substances composed of 2 or more elements
-contains 2+ kinds of atoms |
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-combinations of 2+ substances where each substance retains its own unique identity
-can be separated |
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| law of constant composition |
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Definition
| elemental composition of a pure compound is always the same |
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-changes appearance but not composition
-ex: evaporation of water
-incl all changes of state |
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-aka chemical rxns
-substance is transformed in to chemically different substance
-ex: when hydrogen burns in the air |
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-measure of the amount of material in an object
-base unit is the kilogram |
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| how closely individual measurements agree with one another |
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| how closely individual measurements agree with the correct or "true" value |
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| law of conservation of mass |
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Definition
-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 |
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-extremely small dense region at the center of at atom
-most of the mass of an atom |
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