mixtures - can be separated by physical methods; substances within a mixture retain their individual physical properties, homogeneous mixtures - uniform in composition and properties; also known as solutions, heterogeneous mixtures - a mixture with a non-uniform composition, elements - pure substances made of only one type of atom; cannot be broken down into a simpler type of matter by physical or chemical means, compounds - pure substances that are formed from two or more different types of elements that have been combined chemically in fixed proportions (fixed ratio), acids - aqueous solutions with a pH <7; stronger the acid the lower the number; feel rough, bases - aqueous solutions with a pH >7; greater the number the stronger the base; feel slippery, 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, 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; cannot be changed without changing the actual compound, Law of Conservation of Mass - Mass is NEVER created NOR destroyed and Mass can only be rearranged, chemical reactions - are represented by chemical equations, reactant - substance present before the chemical change occurs, product - substance produced as a result of the chemical change, coefficients - used to represent more than 1 element or compound; if changed do NOT change the actual compound; used to balance a chemical equation,

8th gr Matter & Energy

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