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8th Matter & Energy
Term | Definition |
---|---|
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 |
elements | substance that cannot be broken down into other substances by chemical reactions; classified in a periodic table of elements |
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 |