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Improvements

Improvements. Have students write chemical equations from word equations first, then go the other way. And get a worksheet on these things. Specific Examples for Rules of balancing

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Improvements

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  1. Improvements • Have students write chemical equations from word equations first, then go the other way. And get a worksheet on these things. • Specific Examples for Rules of balancing • Better procession for teaching balancing equations. The worksheet is excellent, but the powerpoint is awful for teaching! • Include Steel wool experiment • Put in water • Put in salt water • Measure change in mass • Measure amount of salt! • Compare how fast they rust • Why do things rust faster when they’re wet anyhow?

  2. Chemical Reactions

  3. Today you are going to…take notes on chemical reactions. So you can…interpret, write, and balance chemical equations You’ll know you’ve got it when you can • Differentiate between chemical & physical changes • Identify the parts of a chemical equation • Define, explain, and give examples of precipitates & catalysts

  4. Physical change –a change in the appearance of something, often easier to “undo” • Ex. • Chemical change – a substance changes into a new substances with new properties (and new chemical formulas). • Ex.

  5. Chemical Reactions • Word Equation – to express the change in words. • Chemical equation – to express the change in formulas.

  6. The parts of a chemical equation • Reactants – chemicals reacting • Products – chemicals produced • Coefficients – big numbers, used to balance equation, how many of each compound/molecule • Subscripts – part of chemical formula, tells how many of each atom is in chemical • Yields – arrow! 2 H20        2 H2   +   O2

  7. States of Matter in Equations H20  (l)       H2 (g)  +   O2 (g)     Liquid water decomposes into hydrogen gas and oxygen gas. (s) - solid (l) - liquid (g) - gas (aq) – aqueous solution (dissolved in water)

  8. Precipitate • A solid produced by mixing two aqueous solutions • A bunch of precipitates video • Lead (II) nitrate in solution reacts with sodium iodide in solution to form lead (II) iodide precipitate and a sodium nitrate solution.

  9. Precipitate • You get gold & precious metals from computers via precipitates!

  10. Bell Work 2/7/14 - min C10H8 (l) + 12 O2 (g)  10 CO2 (g) + 4 H2O (g) • Write the equation above in words. (C10H8 is Naphthalene) • Identify the following in the equation above. • Products, reactants, coefficients, subscripts • What is a precipitate? • What does aqueous mean? • What is a catalyst?

  11. Review Work 2/26 Pt • 2 CO (g) + O2 (g)  2 CO2 (g) • Write a word equation for the reaction above. • Define catalyst • Write the chemical formula of the products & reactants above. • What does aqueous mean? • Define precipitate • Why do equations have to be balanced? (why & what law)

  12. Pt • 2CO (g) + O2 (g)  2CO2 (g) • In presence of a platinum catalyst, gaseous carbon monoxide combines with gaseous oxygen nitrogen to form gaseous carbon dioxide. • A catalyst is something that speeds up or slows down a chemical reaction without chemically changing itself. • Reactants are CO & O2Product is CO2 • Aqueous means “dissolved in water” • A precipitate is the solid formed from a reaction between 2 aqueous solutions. • Equations have to be balanced to be physically accurate/true. If they’re not balanced, they show matter either magically appearing or disappearing, which can’t happen. The law of conservation of mass states that matter cannot be created nor destroyed.

  13. Catalysts • A substance that changes the rate of a chemical reactionwithout being consumed or changed significantly • Positive catalysts - speed up reaction • Lower the amount of energy required to activate the reaction • Negative catalysts, aka “inhibitors” - slow down reaction • Uses • Used in making gasoline, plastics, margarine, beer • In laundry detergents • In living things - enzymes are biological catalysts

  14. Examples of Catalysts • Platinum in catalytic convert reduces NO emissions • In presence of a platinum catalyst, nitrogen monoxide gas decomposes into nitrogen gas and oxygen gas 2NO (g)  N2 (g) + O2 (g) • Platinum decreases CO emissions 2CO (g) + O2 (g)  2CO2 (g) Pt Pt

  15. What’s the word equation? • In presence of sulfuric acid catalyst, ethanol gas reacts with hydrochloric acid gas to form chloroethane and liquid water • In the presence of a vanadium (V) oxide catalyst, sulfur dioxide gas reacts with oxygen gas to produce sulfur trioxide gas.

  16. Reactants being heated • ∆ means the reactants are heated

  17. Elephant Toothpaste • Elephant toothpaste demos! • H2O2 liquid hydrogen peroxide • NaI • Food coloring • Dish soap

  18. Elephant Toothpaste • Elephant toothpaste demos! 2 H2O2(aq) → O2 (g) + 2 H2O(l) NaI

  19. Bell Work 2/11/14 – 5 min Ni N2 (g) + O2 (g)  N2O5 (l) • Write the word equation for the above reaction. • What is the reason for balancing equations? • What is the big difference between a physical & chemical change? (In a chemical change…)

  20. Bell Work 2/11/14 – 5 min Ni N2 (g) + O2 (g)  N2O5 (l) • In the presence of a nickel catalyst, nitrogen gas and oxygen gas yield liquid dinitrogenpentoxide • Conservation of mass – matter can’t be created or destroyed • In a chemical change, a new substance with new chemical properties is created.

  21. Today you are going to…take notes on chemical reactions. So you can…classify and balance chemical equations. You’ll know you’ve got it when you can • State the Law of Conservation of Mass. • Identify & describe the 5 types of reactions. • Balance chemical equations.

  22. 6 Types of Chemical Reactions Synthesis Decomposition Single-Displacement Double-Displacement Acid-Base Combustion

  23. Synthesis What does synthesis mean? Synthetic? Two or more substances combine to form one. A + B ---> AB One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide: Fe + S8 ---> FeS

  24. Decomposition • What does decompose mean? • One complex substance breaks down to make 2 simpler ones. (Opposite of synthesis) AB ---> A + B • Ex: Electrolysis of water to make oxygen and hydrogen gas: H2O ---> H2 + O2

  25. Single-Displacement • What does single mean? • What does displacement mean? • One element trades places with another element in a compound. A + BC ---> AC + B • Ex: when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas: Mg + Be(OH)2 ---> Mg(OH)2 + Be

  26. Double-Displacement The parts of two substances switch places, forming two new substances. AB + CD ---> AD + CB • Ex: the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate: Pb(NO3)2 + 2 KI ---> PbI2 + 2 K(NO3)

  27. Acid-Base A double displacement reaction that takes place when an acid and base react with each other. Makes water (& usually salt). HA + BOH ---> H2O + BA Ex: hydrobromic acid reacts with sodium hydroxide HBr + NaOH ---> H2O + NaBr

  28. Give students something • Can you turn this into water?

  29. Combustion • What does combustion mean? • When oxygen combines with another compound (hydrocarbon) to form water and carbon dioxide. • These reactions are exothermic, meaning they __________________. • Ex: Burning of napthalene: C10H8 (s) + 12 O2 (g)  10 CO2 (g) + 4 H2O (g)

  30. Candle demo! • Pass out candles and jars and ask the groups to make observations...see if they can come to conclusion. So what gases were in the jar? • 2 O2 + CH 4 CO2 + 2 H2O

  31. Combustion • Candle demo • Limiting reactant! • Why do we balance equations? • Jar of alcohol? • Bubble • Soapy hand • Evaporation! • Lycopodium powder

  32. Elephant Toothpaste • Elephant toothpaste demos! 2 H2O2(aq) → O2 (g) + 2 H2O(l) KI

  33. Schedule • Friday • Precipitate Lab • Monday • Demos • 1 more worksheet! • Tuesday • Review for Test • Wednesday • Test

  34. Bell Ringer – 2/12/14 3 Li (s) + AlCl3 (l)  3 LiCl (aq) + Al (g) • In your notes, write the word equation for the chemical reaction above.

  35. Bell Ringer – 2/12/12 3 Li (s) +AlCl3(l)  3 LiCl (aq)+Al (g) Solid lithiumcombined with liquid aluminum chloride yields aqueous lithium chloride andgaseous aluminum.

  36. Schedule • Monday • Return Tests! • Chemical Equation Worksheet #1 • Elephant Toothpaste Lab (Turn in) • Tuesday • Types of equations notes • Balancing Equations • HW: Finish! • Wednesday • Quiz! • Review HW • Practice writing & balancing equations • Thursday • Balance equations: computer lab • Friday • Preview Precipitate lab • Demos! (Write equations) • Monday • Precipitate Lab • Tuesday • Review Precipitate lab • Demos • Review for test • Wednesday • Review for test • Thursday • Test

  37. Law of Conservation of Mass • Toasted cheese sandwich example? Come up with better food

  38. C10H8 + 12 O2  10 CO2 + 4 H2O  + +

  39. Make this with a stick & ball H20        H2   +   O2

  40. Law of Conservation of Mass • Matter cannot be created nor destroyed by ordinary chemical or physical means. • Things can’t just appear from nowhere, nor can they cease to exist. • There have to be the same number of each atom on both sides of an equation. • This is why you have to balance equations.

  41. Bell Work 1/31/13 – 5 min N2 + O2  N2O5 • What type of equation is above? • Nickel acts as a positive catalyst in this equation. What does that mean nickel does? • How could you change the equation to show that nickel is acting as a catalyst? • What is the reason for balancing equations?

  42. Bell Ringer 2/4/13 H2 + 2 O2 2 H2O • The red 2’s in the above equations are _____. • The black 2’s in the above equations are _____. • Something that speeds up or slows down a chemical reaction is a _____. • The above equation is a _____ reaction. • The below equation is a _____ reaction. C10H8 + 12 O2 ---> 10 CO2 + 4 H2O

  43. Bell Work • H2 (g) + N2 (g)  NH3 (g) • Al + H2SO4 Al2(SO4) 3 + H2

  44. H2 (g) + N2 (g)  NH3 (g) • Al + H2SO4 Al2(SO4) 3 + H2

  45. Bell Work 2/6/13 – 3 minutesIdentify & balance • SiCl4 + H2O  SiO2 + HCl 2. NH3 + O2 N2 + H2O

  46. Bell Work 2/9/13 – 3 minutesWrite the word equation and balance it. • Solid magnesiumcombines with oxygen gasto form magnesium oxide. • Solid magnesiumcombines with carbon dioxide gas to form solid magnesium oxideand solid carbon.

  47. 1) synthesis – you make only 1 product Example – burning a piece of magnesium ribbon to make magnesium oxide. 2) decomposition– you start with only one reactant that breaks down. Example – heating copper II carbonate to make copper II oxide and carbon dioxide. 3) Single replacement – an element replaces an element in a compound. Example - Adding a metal to an acid to make a metal chloride and hydrogen gas. 4) Double replacement – two elements in two different compounds switch places. Example – any precipitate reaction 5) Combustion - burning a hydrocarbon to produce carbon dioxide & water

  48. Bell Work 2/13/14 – 5 min Balance AND draw the molecules involved below. H2O + Fe  Fe2O3 + H2

  49. Identify the type of reaction • H2 + 2 O2 2 H2O • C10H8 + 12 O2 10 CO2 + 4 H2O • CO  C + O2 • Li + AlCl3LiCl + Al • B2Br6 + H(NO3)  B(NO3)3 + HBr • H2 + O2 H2O2 • 4 NH3 + 3 O2 2 N2 + 6 H2O

  50. Balancing Equations!

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