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Chemical Equations & Reactions

Learn about chemical reactions and how matter is conserved through the rearrangement of atoms. Explore indications of a chemical reaction and understand the importance of balancing chemical equations.

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Chemical Equations & Reactions

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  1. Chemical Equations & Reactions Materials: Conserving Matter

  2. Chemical Reaction • Process by which one or more substances are changed into one or more different substances

  3. Indications of a Chemical Reaction • Evolution of heat & light

  4. Indications of a Chemical Reaction • Production of a gas

  5. Indications of a Chemical Reaction • Formation of a precipitate

  6. Indications of a chemical reaction • Change in color. (sumac leaves change color when chlorophyll is destroyed)

  7. Chemical Reactions • There are many ways where matter seems to disappear: • The consumption of fuel by your car. • The lunch you ate today. • The rusting away of your car. • Do they really disappear? • NO

  8. Chemical Equation • Reactants  Products • Follows the Law of Conservation of Mass

  9. Chemical Reactions • Law of Conservation of Matter: in a chemical reaction, matter in neither created nor destroyed; the molecules are merely rearranged • atoms are forever! • you should be able to account for every individual atom in a chemical reaction

  10. Word Equation Writing Chemical Equations • Represents facts- only qualitative • Example: Methane + oxygen  carbon dioxide + water

  11. Writing Chemical Equations Formula Equation Example: CH4(g) + O2(g) CO2(g) + H2O(g) (not balanced) Symbols you will see in equations

  12. Writing Chemical Equations BalancedFormula Equation • Inserting Coefficients-small whole # that appears in front of a formula • Multiplies number of atoms of each element indicated in chemical formula • Example: CH4(g) + 2O2(g) CO2(g) + 2H2O(g)

  13. Atom Inventory • Name the number and type of atoms in AgNO3 (NH4)2CO3 6 H2O

  14. Atom Inventory • In order to follow the law of conservation- • there must be the same number and type of atoms on both sides of the equation.

  15. Atom Inventory • Is this equation balanced? • Take an atom inventory Mg + O2 MgO yes no 2NaOH  Na2O + H2O yes no Mg + Cl2  MgCl2 yes no

  16. Balancing Chemical Equations Balance the formula equation according to the law of conservation of mass • Balance the different types of atoms one at a time • Balance polyatomic ions that appear on both sides of the equation as single units • Balance H atoms and O atoms after atoms of all other elements have been balanced

  17. Examples Mg + HCl  MgCl2 + H2 Al2(SO4)3 + Ca(OH)2 Al(OH)3 + CaSO4 MgI2 + KNO3 KI + Mg(NO3)2

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