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Chemical reactions and equations


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Chemical reactions and equations

  1. 1. Chemical Reactions and Equations<br />CLASS NOTES<br />Wed. Sept. 29th/Thurs. Sept. 30, 2010<br />
  2. 2. Review from last class <br />What types of changes can occur as a result of chemical reactions? <br />Can you give an example?<br />Physical changes!<br />Chemical changes!<br />
  3. 3. What is involved in a chemical reaction?<br />There are two parts to a chemical reaction:<br />Reactants and Products<br />Reactants are those substances you begin with <br />Products are the substances formed by the reactionReactant1 + reactant2  products<br />For example:<br />sodium (Na) + chlorine (Cl₂)  sodium chloride (NaCl)<br />
  4. 4. Chemical equations<br />Chemical reactions are written using equations, with reactants on one side and products on the other:<br />Word equations! <br />e.g. sodium + chlorine  sodium chloride carbon + oxygen  carbon dioxidecalcium + oxygen  calcium oxide <br />Usually written with chemical formulas (symbols):<br />Ex.Na + Cl NaClC + O₂  CO₂Ca+ O  CaO<br />
  5. 5. Chemical equations continued…<br />The numbers of atoms on each side of the chemical equation is equal to the other side:<br />Reactant1 + reactant 2  product <br /> is the same as equals, or produces<br />
  6. 6. Endothermic and Exothermic Reactions<br />In a chemical reaction, some bonds in the reactants break and new bonds form in the products<br />Breaking and creating bonds requires energy<br />Two types of chemical reactions:<br />Absorbs energy = endothermic (energy in = ENtrance)<br />Releases energy = exothermic (energy EXits)<br />