elements - pure substances made of only one type of atom, periodic table of elements (PT) - organized table of chemical elements; allows the whole world to have a common language as reference for elements, chemical symbol - represent elements on the periodic table; can be 1 or 2 letters 1st letter is ALWAYS CAPITAL, if 2nd letter it is always lowercase, atom - the smallest part of an element, compounds - formed from two or more different types of elements that have been combined chemically in fixed proportions, chemical formulas - the chemical symbols of the atoms of the elements present in the compound, subscripts - small numbers after an element that tell the number of atoms of that element present, molecules - two or more of the same type of element are chemically combined, like O2, H2, O3, N2, physical property - a quality or a condition of a substance that can be observed or measured without changing the substance’s composition; the arrangement of the atoms does not change, chemical property - describes the ability of one substance to change into a different substance; the arrangement of atoms changes, physical change - a change that does not alter the chemical identity of a substance, chemical change - occurs when one or more substances change into one or more different substances, reactant - substance present before the chemical change occurs, product - substance produced as a result of the chemical change,

7th gr Pure Substances

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