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  1. 1. <ul><li>Notes: Chemical Reactions </li></ul><ul><li>CW: Types of Reactions </li></ul><ul><li>H: Types of Chemical Reactions </li></ul>
  2. 2. Chemical Reactions January 28, 2010
  3. 3. Objectives <ul><li>Identify parts of a chemical equation </li></ul><ul><li>Recognize four types of chemical reactions </li></ul><ul><li>Describe Law of Conservation of Mass </li></ul>
  4. 4. Molecules and Compounds Some elements exist as individual atoms. Molecules consist of two or more elements joined together. If more than one type of atom is in a molecule, we call it a compound .
  5. 5. Chemical Reactions Chemical reactions happen when the atoms in one or more molecules split up and join together in new ways. For example, hydrogen can react with oxygen :
  6. 6. <ul><li>When a reaction takes place, things happen. There may be a gas given off, a color change or a solid material appearing. There could also be changes we can’t see, such as a temperature change. </li></ul><ul><li>The mass of the reactants (the chemicals we start with) is always the same as the mass of the products (the chemicals we end with). </li></ul>Law of Conservation of Mass
  7. 8. Chemical Equations <ul><li>On the left are the reactants – the starting materials </li></ul><ul><li>On the right are the products – the new substances that are formed </li></ul><ul><li>An arrow connects the two sides – read as yields or produces </li></ul>AgNO 3 + NaCl  AgCl + NaNO 3 Read left to right like a sentence in chemical terms
  8. 10. 4 Types of Reactions Synthesis Decomposition Single Replacement Double Replacement
  9. 12. Synthesis Means to put together or combine occur when two substances (generally elements ) combine and form a compound. In general: A + B  AB Fe + S  FeS reactant + reactant  1 product
  10. 13. Decomposition In this type of reaction, a substance breaks down into simpler parts when it is heated. 1 Reactant  Product + Product In general: AB  A + B CuCO 3 heat Cu 2 O + CO 2 For example, copper carbonate will decompose when heated :
  11. 14. Single Replacement In a displacement reaction, one metal ‘kicks out’ a less reactive one. The iron wants to be with the sulphate more than the copper does. We say that iron is more reactive than copper. element + compound  element + compound <ul><ul><li>In general: </li></ul></ul><ul><ul><li>A + BC  AC + B </li></ul></ul>Fe + CuSO 4 Cu + FeSO 4
  12. 15. Double Replacement Occurs when one metal trades places with another one. AgNO 3 + KCl  AgCl + KNO 3 Compound + compound  product + product In general: AB + CD  AD + CB