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Chemistry Notes – Chemical Reactions and Equations

Chemistry Notes – Chemical Reactions and Equations. Changes of Matter. Chemical Change - When a substance is changed to a new form, but its molecules are different from before, and can’t be changed back. Describes its ability to change. Flammability, ability to react

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Chemistry Notes – Chemical Reactions and Equations

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  1. ChemistryNotes – Chemical Reactions and Equations

  2. Changes of Matter • Chemical Change - When a substance is changed to a new form, but its molecules are different from before, and can’t be changed back. • Describes its ability to change. Flammability, ability to react • Examples: When substances are burned or chemically react. Burning paper, iron rusting, fireworks exploding.

  3. Chemical change • In a chemical change – the atoms are rearranged to form new substances with different chemical and physical properties • The substances that undergo change in a chemical reaction are called reactants.

  4. Chemical change • The substances that undergo change in a chemical reaction are called reactants. • The new substances formed by the reaction are called products • Baking soda + vinegar Reactants • Bubbles • Carbon dioxide + sodium acetate Products

  5. Chemical change • The substances that undergo change in a chemical reaction are called reactants. • The new substances formed by the reaction are called products • NaHCO3 + H2C2H3O2 Reactants • CO2 + NaC2H3O2 Products

  6. Chemical Bonds – Chemical forces which hold atoms together and form complete electrons shells Octet Rule – The outside shell holds a maximum of 8 electrons. Atoms will lose, gain, or share electrons to reach the octet number and become stable.

  7. H2 – Hydrogen gas O2 – Oxygen gas NaCl – Table Salt

  8. v v

  9. Chemical Reactions and Equations

  10. Chemical Reactions • Chemical reactions involve changes in properties and changes in energy that you can observe. • Examples of reactions: • 1) Color change (may involve an indicator) • 2) Precipitate – a solid that forms from two solutions • 3) Temperature change- produces heat (exothermic) becomes colder (endothermic) • 4) Production of gas – contents bubble or fizz

  11. Chemical Equations - Show what takes place in chemical reactions . Matter and mass are the same before and after a reaction Reactants Products Original substances = What are produced What is used yields or = equalsC + O2 = CO2 one atom Carbon 1 molecule 1 molecule or 2 atoms carbon dioxide oxygen Total atoms/elements on the left= equals to total number of atoms/elements on the right

  12. 2Na + Cl2 = 2NaCl Sodium Chlorine Sodium Chloride (Salt) 2 Na 2 Cl 2 Na 2 Cl Energy Release Exothermic - Gives off or releases energy (burning) Reactants Product + energy Endothermic – Absorbs energy ( ice pack, photosynthesis) Reactants + energy Product

  13. Types of Reactions 1) Synthesis – One product from two reactants H2 + O2 = H2O Polymerization - Smaller molecules join to form one large molecule.

  14. Types of Reactions 1) Synthesis – One product from two reactants H2 + O2 = H2O Hydrogen + Oxygen = Water (Dihydrogen monoxide) Polymerization - Smaller molecules join to form one large molecule.

  15. Types of Reactions 1) Synthesis – One product from two reactants H2 + O2 = H2O Hydrogen + Oxygen = Water (Dihydrogen monoxide) C + O2 = CO2 endo- or exo- ? Polymerization - Smaller molecules join to form one large molecule.

  16. Types of Reactions 2) Decomposition – Two or more products from one reactant CuO Cu + O2

  17. Types of Reactions 2) Decomposition – Two or more products from one reactant CuO Cu + O2 Copper(II) Oxide Copper + Oxygen

  18. Types of Reactions 3) Displacement – Two reactants form two new products Single Displacement: Cu + Ag(NO3) Ag + Cu(NO3)2

  19. Types of Reactions 3) Displacement – Two reactants form two new products Single Displacement: Cu + Ag(NO3) Ag + Cu(NO3)2 Copper(I) + Silver Nitrate Silver + Copper(I) Nitrate

  20. Types of Reactions 3) Displacement – Two reactants form two new products Double Displacement: KI + Pb(NO3) 2 K(NO3) + PbI2 CH4 + O2 CO2 + H2O

  21. Types of Reactions 3) Displacement – Two reactants form two new products Double Displacement: KI + Pb(NO3) 2 K(NO3) + PbI2 Potassium + Lead Nitrate Potassium Nitrate + Lead Iodide Iodide CH4 + O2 CO2 + H2O Carbon + Oxygen Carbon Dioxide + Dihydrogen tetrahydride monoxide

  22. Types of Reactions 3) Displacement – Two reactants form two new products Double Displacement: K2Cr2O7 + Ca(OH)2 KOH + CaCr2O7

  23. Types of Reactions 3) Displacement – Two reactants form two new products Double Displacement: K2Cr2O7 + Ca(OH)2 KOH + CaCr2O7

  24. Types of Reactions 3) Displacement – Two reactants form two new products Double Displacement: K2Cr2O7 + Ca(OH)2 KOH + CaCr2O7 Potassium Calcium Potassium Calcium dichromate hydroxide hydroxide dichromate

  25. Chemical Equations • Chemical equations use chemical formulas and other symbols instead of words to summarize a reaction Reactant + Reactant = Product + Product Cu + Ag(NO3) = Copper + Silver Nitrate Ag + Cu(NO3)2 Silver + Copper Nitrate

  26. Stoichiometry: Balancing equations – Uses coefficients and chemical formulas to show a balanced reaction • Law of Conservation of Mass - The amount of matter before a reaction is equal to the amount after (same # and types of atoms) H2O H2 + O2

  27. Rules for equations • 1) Formulas reacting are to the left of the arrow or equal sign • 2) Formulas of molecules produced are on the right side • 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right • 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. • 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2F2, Cl2, Br2, I2 - Halogens Reactants Products H2O = H2 + O2 CuO =Cu + O2

  28. Rules for equations • 1) Formulas reacting are to the left of the arrow or equal sign • 2) Formulas of molecules produced are on the right side • 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right • 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. • 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2F2, Cl2, Br2, I2 - Halogens Reactants Products H2O = H2 + O2 2-H,1-0 2-H,2-O CuO =Cu + O2

  29. Rules for equations • 1) Formulas reacting are to the left of the arrow or equal sign • 2) Formulas of molecules produced are on the right side • 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right • 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. • 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2F2, Cl2, Br2, I2 - Halogens Reactants Products H2O = H2 + O2 2-H,1-0 2-H,2-O CuO =Cu + O2 1-Cu, 1-O 1-Cu,2-O

  30. Rules for equations 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right 4) Equations are balanced by changing coefficients. Subscripts of molecules or compoundscannot be changed. • 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2F2, Cl2, Br2, I2 - Halogens Reactants Products H2O = H2 + O2 2-H,1-0 2-H,2-O CuO =Cu + O2 1-Cu, 1-O 1-Cu,2-O

  31. Rules for equations 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. • 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2F2, Cl2, Br2, I2 - Halogens Reactants Products 2H2O = 2H2 + O2 2-H,1-0= 2-H,2-O 4-H,2-O = 4-H,2-0 CuO =Cu + O2 1-Cu, 1-O =1-Cu,2-O

  32. Rules for equations 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. • 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2F2, Cl2, Br2, I2 - Halogens Reactants Products 2H2O = 2H2 + O2 2-H,1-0= 2-H,2-O 4-H,2-O = 4-H,2-0 2CuO =2Cu + O2 1-Cu, 1-O = 1-Cu,2-O 2-Cu, 2-O = 2-Cu,2-0

  33. Rules for equations 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. 5) All gases except Noble Gases VIII (He,Ne, Ar) occur in paired molecules: O2, H2, N2 F2, Cl2, Br2, I2 - Halogens Nitrogen + Hydrogen = Nitrogen trihydride (ammonia) (g) = gas (l) = liquid (s) = solid (aq) = aqueous solution

  34. Rules for equations 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. 5) All gases except Noble Gases VIII (He,Ne, Ar) occur in paired molecules: O2, H2, N2 F2, Cl2, Br2, I2 - Halogens Nitrogen + Hydrogen = N2 + H2 = NH3 Nitrogen trihydride (ammonia) Hydrogen + Chlorine = Hydrogen Chloride

  35. Rules for equations 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. 5) All gases except Noble Gases VIII (He,Ne, Ar) occur in paired molecules: O2, H2, N2 F2, Cl2, Br2, I2 - Halogens Nitrogen + Hydrogen = N2 + H2 = NH3 Nitrogen trihydride (ammonia) Hydrogen + Chlorine = H2 + Cl2 = HCl Hydrogen Chloride

  36. Rules for equations 3) Total number of atoms used = total # produced. The number of each element or molecule on the left = # on the right 4) Equations are balanced by changing coefficients. Subscripts of molecules cannot be changed. • 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2 F2, Cl2, Br2, I2 - Halogens Pure metals are written as single elements. Silver = Ag Potassium = K (g) = gas (l) = liquid (s) = solid (aq) = aqueous solution

  37. Rules for equations 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2 F2, Cl2, Br2, I2 - Halogens Pure metals are written as single elements. Silver = Ag Potassium = K • Oxygen (g) = • Chlorine (g) = • Bromine (l) = • Copper (s) = • Calcium (s) = (g) = gas (l) = liquid (s) = solid (aq) = aqueous solution

  38. Rules for equations 5) All gases except Noble Gases VIII (He, Ne, Ar) occur in paired molecules O2, H2, N2 F2, Cl2, Br2, I2 - Halogens Pure metals are written as single elements. Silver = Ag Potassium = K • Oxygen (g) = O2 • Chlorine (g) = Cl2 • Bromine (l) = Br2 • Copper (s) = Cu • Calcium (s) = Ca (g) = gas (l) = liquid (s) = solid (aq) = aqueous solution

  39. Rules for equations • All gases except Noble Gases VIII (He,Ne, Ar) occur in paired molecules: O2, H2, N2 F2, Cl2, Br2, I2 - Halogens Pure metals are written as single elements. Silver = Ag Potassium = K 6) Polyatomic ions in a displacement reaction can be counted as a group when counting atom/molecule #’s Nitrogen + Hydrogen =Nitrogen trihydride (ammonia) N2 + H2 = NH3 Hydrogen + Chlorine =Hydrogen Chloride H2 + Cl2 = HCl KI + Pb(NO3) 2 = K(NO3) + PbI2 K2Cr2O7 + Ca(OH)2 = KOH + CaCr2O7

  40. Balancing Equations • 1) Write the equation • 2) Count the atoms • 3) Use coefficients to balance the atoms Copper(II) Oxide Copper + Oxygen

  41. Balancing Equations • 1) Write the equation • 2) Count the atoms • 3) Use coefficients to balance the atoms Copper(II) Oxide Copper + Oxygen CuO Cu + O2

  42. Balancing Equations 1) Write the equation 2) Count the atoms 3) Use coefficients to balance the atoms CuO Cu + O2

  43. Balancing Equations • 1) Write the equation • 2) Count the atoms • 3) Use coefficients to balance the atoms Nitrogen + Hydrogen = Nitrogen trihydride(ammonia)

  44. Balancing Equations • 1) Write the equation • 2) Count the atoms • 3) Use coefficients to balance the atoms Nitrogen + Hydrogen = Nitrogen trihydride(ammonia) N2+ H2 = NH3

  45. Balancing Equations • 1) Write the equation • 2) Count the atoms • 3) Use coefficients to balance the atoms Potassium + Chlorine = Potassium chloride

  46. Balancing Equations 1) Write the equation 2) Count the atoms 3) Use coefficients to balance the atoms Potassium + Chlorine = Potassium chloride K + Cl2 = KCl

  47. Balancing Equations 1) Write the equation 2) Count the atoms 3) Use coefficients to balance the atoms K2Cr2O7+ Ca(OH)2 = KOH + CaCr2O7

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