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Learn about chemical reactions and how they cause changes in energy, create new substances with different properties, and how to write chemical equations to represent these reactions using both word and formula methods.
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how a chemical change happens • also causes a change in energy • energy can be absorbed or released • a new substance is created • Chemical Reactions
Reactants • starting materials • on the left side of the arrow in a chemical equation • ex. Mg + HCl MgCl2 + H2
Products • the new substances created • have different properties than reactants • ex. Mg + HClMgCl2 + H2
Chemical Equations • uses either chemical symbols or words to show reactions Formula Equation: Na + Cl2NaCl Word Equation: sodium + chlorine gas sodium chloride
Writing Word Equations • write the word equation • underline the reactants and circle the products • Aluminum metal combines with chlorine gas to make aluminum chloride • Magnesium metal combines with nitrogen gas to make magnesium nitride.
Writing Formula Equations • write the chemical symbol for each element(s) in the compound • criss-cross to get the right formula • sodium + chlorine sodium chloride • fluorine + calcium bromide bromine + calcium fluoride