Chemical reactions

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Chemical reactions

  1. 1. Agenda • Atoms and the Periodic table Jeopardy • Notes: Chemical Equations and Reactions • Molecular models • Model and Change Quiz tomorrow Bell Work • Draw both the Bohr model and the Lewis dot model of the following: – – – – – Aluminum Carbon Arsenic Argon helium
  2. 2. Chemical Equations and Reactions April 2, 2013
  3. 3. Objectives 1. Explain the difference between elemental and chemical formula 2. Recognize all the parts of a chemical equation 3. Describe how compounds are different than the materials that compose it 4. Balance Chemical Equations
  4. 4. Chemical Bonding The attraction between two atoms that holds them together Chemical changes occur because of breaking and rearrangement Chemical change = chemical reaction
  5. 5. Chemical Equation To show chemical reactions we use chemical equations C + O2 --> CO2 4 Al (s) + 3 O2 (g) ---> 2 Al2O3 (s)
  6. 6. Parts of Chemical Equation Elemental formula: how atoms are bounded together in an element   Li O2 , N2 , S8
  7. 7. Chemical formula: representation of a compound, when atoms of different elements bond to each other  NaCl, NH3 , CO2
  8. 8. Subscript: represents how many of a particular atom Coefficient: represents how many of a particular element or molecule
  9. 9. (s) represents solid (l) represents liquid (g) represents gas (aq) represents aqueous
  10. 10. How many atoms? C + O2 --> CO2 4 Al (s) + 3 O2 (g) ---> 2 Al2O3 (s)
  11. 11. Chemical Equation Reactants --> Products C + O2 --> CO2 when reading an equation Arrow = yields
  12. 12. Law of Conservation of Mass Matter is neither created nor destroyed during a chemical reaction Therefore all chemical equations must be balanced; equal atoms of each element on each side
  13. 13. Balancing equation rules You may change the coefficients in front You may NOT change the subscripts Changing the subscript changes the compound
  14. 14. Steps of balancing 1. Write the correct formulas for the equation. Once written do not change the formula’s 2. Find the number of atoms on the left side of each element and compare it against the number of atoms of the same elements on the right side
  15. 15. 4. Check your answer to see if:  The numbers of atoms on both sides of the equation are now balanced.  The coefficients are in the lowest possible whole number ratios. (reduced)
  16. 16. Helpful hints Take one element at a time working left to right, Leave H for next to last and O last IF everything balances except for O, and there is no way to balance O with a whole number, double all the coefficients and try again.
  17. 17. Balancing Equations ___ H2(g) + ___ O2(g) ---> ___ H2O(l) One of the oxygen atoms binds with two of the hydrogen atoms
  18. 18. Done Activities Which equations are balanced? Balance the ones that aren’t a.Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g) b. Al(s) + Br2(l)  Al2Br6(s) c. HgO(s)  Hg(l) + O2(g)
  19. 19. ___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s)
  20. 20. ____C3H8(g) + _____ O2(g) ----> _____CO2(g) + _____ H2O(g) ____B4H10(g) + _____ O2(g) ----> _____B2O3(g) + _____ H2O(g)

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