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2.1 Science and Technology in Society 2.2 Changes in Matter 2.3 Balancing Chemical Reactions

2.1 Science and Technology in Society 2.2 Changes in Matter 2.3 Balancing Chemical Reactions 2.4 Chemical Amount 2.5 Classifying Chemical Reactions 2.6 Chemical Reactions in Solution. Chemical Reactions. 2.2 Changes in Matter. Types of Changes in Matter. Physical Changes Change in State

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2.1 Science and Technology in Society 2.2 Changes in Matter 2.3 Balancing Chemical Reactions

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  1. 2.1 Science and Technology in Society 2.2 Changes in Matter 2.3 Balancing Chemical Reactions 2.4 Chemical Amount 2.5 Classifying Chemical Reactions 2.6 Chemical Reactions in Solution

  2. Chemical Reactions 2.2 Changes in Matter

  3. Types of Changes in Matter • Physical Changes • Change in State • No new substance

  4. Types of Changes in Matter • Nuclear Changes • Changes within the nucleus • Fusion and Fission (applets)

  5. Types of Changes in Matter • Chemical Changes • A change in chemical bonds • Hoffman Demo

  6. Signs of a Chemical Change • Production of heat and light • Formation of a gas • Formation of a precipitate • Colour change

  7. Why Do Reactions Occur? • The kinetic molecular theory states that matter is made up of tiny particles in continuous random motion. • The average kinetic energy (the energy of motion) of the particles depends on the temperature of the particles.

  8. Solid     LiquidGas

  9. Types of Particle Motion • Translational motion: the motion of a particle in a straight line • Rotational movement: a spinning or turning of a molecule.

  10. Motion Continued: • Vibrational movement: the back and forth motion within a molecule • These types of particle movement can be discussed with the three states of matter

  11. KMT Continued: • The particles this theory refers to may be atoms (Na), ions (Na+) or molecules (CO2). • As the particles move, they collide with each other and objects in their path.

  12. Collision Theory • Reaction rate depends on the collisions between reacting particles. • Successful collisions occur if the particles... • collide with each other • have the correct orientation • have enough kinetic energy to break bonds

  13. Collision Theory Activation Energy • Activation Energy (Ea) • minimum energy required for a reaction to occur

  14. Collision Theory Ea • Activation Energy • depends on reactants • low Ea = fast rxn rate

  15. Factors Affecting Rxn Rate • Surface Area • high SA = fast rxn rate • more opportunities for collisions • Increase surface area by… • using smaller particles • dissolving in water

  16. Factors Affecting Rxn Rate • Concentration • high conc = fast rxn rate • more opportunities for collisions

  17. Factors Affecting Rxn Rate • Temperature • high temp = fast rxn rate • high KE • fast-moving particles • more likely to reach activation energy

  18. Factors Affecting Rxn Rate • Temperature Analogy: 2-car collision 5 mph “fender bender” 50 mph “high-speed crash”

  19. Factors Affecting Rxn Rate • Catalyst • substance that increases rxn rate without being consumed in the rxn • lowers the activation energy • Burn a sugar cube with a catalyst

  20. Exothermic Reaction energyreleased • reaction thatreleases energy • products have lower energy than reactants 2H2(l) + O2(l)  2H2O(g) + energy

  21. Endothermic Reaction energyabsorbed • reaction that absorbs energy • reactants have lower energy than products 2Al2O3+ energy 4Al + 3O2

  22. Law of Conservation of Mass • mass is neither created nor destroyed in a chemical reaction • total mass stays the same • atoms can only rearrange 4 H 2 O 4 H 2 O 36 g 4 g 32 g

  23. Chemical Reactions 2.3 Balancing Chemical Reaction Equations

  24. Chemical Equations • Chemical reactions are represented by chemical equations • A chemical equation lists all of the compounds that participate in the reaction.

  25. Chemical Equations A+B  C+D REACTANTS PRODUCTS

  26. Chemical Equations

  27. Writing Equations 2H2(g) + O2(g)  2H2O(g) • Identify the substances involved. • Use symbols to show: • How many? - coefficient • Of what? - chemical formula • In what state? - physical state

  28. Writing Equations Two atoms of aluminum react with three units of aqueous copper(II) chloride to produce three atoms of copper and two units of aqueous aluminum chloride. • How many? • Of what? • In what state?  3 2 Al (s) + 3 CuCl2 (aq) Cu (s) + 2 AlCl3 (aq)

  29. Describing Equations Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g) to produce • How many? • Of what? • In what state? One mole of solid zinc reacts with two moles of aqueous hydrochloric acid one mole of aqueous zinc chloride and one mole of hydrogen gas.

  30. Balancing Steps 1. Write the unbalanced equation. 2. Count atoms on each side. 3. Add coefficients to make #s equal. Coefficient  subscript = # of atoms 4. Reduce coefficients to lowest possible ratio, if necessary. 5. Double check atom balance!!!

  31. Helpful Tips • Balance one element at a time. • Update ALL atom counts after adding a coefficient. • If an element appears more than once per side, balance it last. • Balance polyatomic ions as single units. • “1 SO4” instead of “1 S” and “4 O”

  32. Balancing Example Al + CuCl2 Cu + AlCl3 Al Cu Cl Aluminum and copper(II) chloride react to form copper and aluminum chloride. 2 3 3 2  2  6 1 1 1 1 2 3 2  3  6   3

  33. 2.4 Chemical Amount The Mole

  34. VERY A large amount!!!! What is the Mole? • A counting number (like a dozen) • Avogadro’s number (NA) • 1 mol = 6.02  1023 items

  35. A mole of a compound is an observable quantity. It can be weighed and used in experiments. LEFT: Proceeding clockwise from the top, samples containing one mole each of copper, aluminum, iron, sulfur, iodine, and (in the center) mercury.

  36. HOW LARGE IS IT??? A. What is the Mole? • 1 mole of pennies would cover the Earth 1/4 mile deep! • 1 mole of hockey pucks would equal the mass of the moon! • 1 mole of basketballs would fill a bag the size of the earth!

  37. One mole = 6.02 x 1023 atoms, molecules, or ions (Avogadro’s number) • When coefficients are used to balance chemical equations, they express a mole-to-mole ratio of the products and reactants.

  38. These numbers do not represent the exact number of moles for the reactants or products, but rather give a ratio we can use to compare quantities.

  39. Molar Mass • Mass of 1 mole of an element or compound. • Atomic mass tells the... • atomic mass units per atom (amu) • grams per mole (g/mol) • Round to 2 decimal places

  40. Molar Mass Examples 12.01 g/mol 26.98 g/mol 65.39 g/mol • carbon • aluminum • zinc

  41. Molar Mass Examples • water • sodium chloride • H2O • 2(1.01) + 16.00 = 18.02 g/mol • NaCl • 22.99 + 35.45 = 58.44 g/mol

  42. Molar Mass Examples • sodium bicarbonate • sucrose • NaHCO3 • 22.99 + 1.01 + 12.01 + 3(16.00) = 84.01 g/mol • C12H22O11 • 12(12.01) + 22(1.01) + 11(16.00) = 342.34 g/mol

  43. MASS IN GRAMS MOLES NUMBER OF PARTICLES Molar Conversions molar mass 6.02  1023 (g/mol) (particles/mol)

  44. Molar Conversions n = m/M n = number of moles m = mass (g) M = Molar Mass (g/mol)

  45. Molar Conversions p = n * NA n = number of moles p = particles NA = Avogadro's number (6.02 x 1023 particles per mole)

  46. Molar Conversion Examples • How many moles of carbon are in 26 g of carbon? 26 g C 1 mol C 12.01 g C = 2.2 mol C

  47. Molar Conversion Examples • How many molecules are in 2.50 moles of C12H22O11? 6.02  1023 molecules 1 mol 2.50 mol = 1.51  1024 molecules C12H22O11

  48. Molar Conversion Examples • Find the mass of 2.1  1024 molecules of NaHCO3. 2.1  1024 molecules 1 mol 6.02  1023 molecules 84.01 g 1 mol = 290 g NaHCO3

  49. Chemical Reactions 2.5 Classifying Chemical Reactions

  50. Combustion • the burning of any substance in O2 to produce heat A + O2 B CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)

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