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QOTD 5/13/14

QOTD 5/13/14. Please have your homework (back of yesterday’s activity sheet) out to be checked off. QOTD: Based on what we saw in the lab yesterday, what do you think the difference is between an acid and a base? Write down your response.

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QOTD 5/13/14

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  1. QOTD 5/13/14 Please have your homework (back of yesterday’s activity sheet) out to be checked off. QOTD: Based on what we saw in the lab yesterday, what do you think the difference is between an acid and a base? Write down your response. After you have a written answer, turn and talk with your partner about this.

  2. Demos! 1. rainbow 2. T shirt vs sulfuric acid

  3. Wear your goggles when we have acids and bases out!

  4. HW answers List 4 properties of acids • Taste sour (like vinegar and lemon juice) • Turn cabbage juice pink/purple • Turn universal indicator red/orange/yellow • pH below 7 List 4 properties of bases • pH above 7 • Turn cabbage juice blue/green • Turn universal indicator blue/purple • Feel slippery (like soap)

  5. Learning Target • You should be able to compare and contrast the Arrhenius and Bronsted-Lowry definitions of acids and bases. You should also be able write equations to show how water interacts with acids and bases.

  6. Activity • Turn to p. 53. Read this page then answer the reading summary Qs on p. 54. • Then move on to answer the remaining Questions on p. 54-55. • We will debrief these Qs in 5 minutes. • If you finish early, read the rest of p. 55 and 56.

  7. Reading Summary Answers p. 54 1. What are some observable properties of acids and bases? Acids taste sour Bases taste bitter and feel slippery (because they turn the oils in your skin into soap!) Many acids and bases don’t have a color! But we can use indicators to tell if we have an acid or base 2. What is the pH scale? A number scale to tell how acidic or basic a substance is. Acid = below 7 (lower = more acidic) Base = above 7 (higher = more basic) • What does it mean to say a substance has a neutral pH? It has a pH of 7

  8. Reading Summary Answers p. 54 • Classify each of the following as acidic, basic, or neutral. • Lemon juice tastes sour Sour = acid b. A solution turns cabbage juice green Green = base • Solution of potassium hydroxide feels slippery Slippery = base (turns oil into soap!) d. Sugar solution has pH of 7 pH 7 = neutral • Drain cleaner has pH of 12 pH above 7 = base

  9. Exploring acid and base theories p. 54-55:ACIDS • What element do acids all have in common? Hydrogen 2. What patterns do you notice in the way the molecular formulas are arranged? They usually start with H (or have COOH). They all form H+ ions in solution.

  10. Exploring acid and base theories p. 54-55: BASES 3. What ions do you notice in the base solutions? They all have hydroxide ions (OH-) 4. If the OH- in the ammonia and sodium carbonate solutions was not part of the original formula, where od you think the atoms in the hydroxide came from? WATER! Notice that water can make both H+ and OH-

  11. Acid and Base Theories • read the rest of p. 55-56. We will work out one of the problems on p. 57 together in about 3 minutes. 2. Finish the problems on p. 57 • Read the rest of p. 57-58 and draw pictures of strong and weak acid dissociation on p. 58 (and define dissociation) • We will debrief these in about 10 minutes. • If you finish early, ask me for the homework sheets

  12. p. 57 answers • HC2H3O2 + H2O  C2H3O2- + H3O+ Acid = proton donor: HC2H3O2 gave H+ to water 2. CH3NH2+ H2O  CH3NH3+ + OH- Base = proton acceptor (HC2H3O2 accepted H+ from water) Notice that water can either give or accept depending on the conditions! We call this “amphoteric”

  13. p. 57 answers • H2C2O4 + H2O  HC2O4- + H3O+ Acid = proton donor: H2C2O4 gave H+ to water 2. C2O42-+ H2O  HC2O4-+ OH- Base = proton acceptor (HC2H3O2 accepted H+ from water) Notice that both reactions produced HC2O4- . Also note that these are REVERSIBLE reactions…. So what word can we use to describe HC2O4-? AMPHOTERIC!

  14. Strong and weak acids answers DISSOCIATION = breaking apart into ions when dissolved in water. For example: NaCl (s)  Na+ (aq) + Cl-(aq) Strong acid dissociation: 100% ions , 0% not dissociated 100% H+ (aq) + Br- (aq) with 0% HBr (aq) Weak acid dissociation: some ions, MOSTLY not dissociated A mixture of: H+ (aq) + F- (aq) + HF (aq)

  15. Homework • p. 59 (due tomorrow) • Soap reading and Qs (due tomorrow) • Chemistry in MY Life Posters (due Monday!)

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