Rates of Reaction

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Rates of Reaction

• A Lab Investigation

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Schedule of the Week 3/6-3/13/08

• Thur Review 9E / Introduce Reaction Rates Lab /
  Asmt Page 737 12, 743 1 EXPLAIN
• Mon Practice collecting lab data / Asmt Write
  detailed lab procedures.
• Tues Collect excellent lab data / Asmt
  Prepare results graph to share with class
• Wed Wrap up lab / Review graphical results /
  Asmt Practice Exam / Lab Report due Monday (10
  XC if Early!)
• Thur Unit 5 Review / Asmt 3x5 card
• Fri Unit 5 Exam / Asmt Lab Report

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Monday 2/25/08

• Prep
• Get 30 copies of each lab handout temp, conc,
  surface area metal type
• Set up demo of reaction of HCl Zn
• Class
• DMA Schedule of Week (Pass back papers) Remind
  students of lab fee.
• Demo under camera HCl Zn
• Determine balanced chemical equation.
• How measure rate of reaction?
• What factors might influence rate of reaction?
• Choose which pair will investigate which factor
  every 4 tables will choose a different factor.
• Write hypothesis, manipulated responding
  variables, variables to control
• Asmt Draft Procedures (Include at least 5
  different levels repeat the experiment)

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How can we measure the rate of a reaction?

• In math rate distance/time
• In life rate anything changing/time
• How can we measure the rate of the reaction
• Zn(s) 2HCl(aq) ? ZnCl2(aq) H2(g)
• Draw observe the standard set up for this lab.
• Measure the zinc consumption or gas production
  versus time.

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Standard Reaction Rate Set Up
Rubber tubing
Glass tube
One-hole stopper
10ml graduated cylinder
Test-tube
beaker
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Materials Available

• 1 M HCl (several liters)
• 6 M HCl (500 mL)
• Distilled water (several liters)
• 1 cm2 Al foil squares (lots of these per class)
• Mossy Zn
• Mg ribbon
• Fe filings (20,30,4050mesh)
• Sn pieces
• Cu wire pieces

• Marble chips for waste bucket
• Timing devices
• Hot plates
• Ice
• Beakers for water bathsThermometers
• Each pair will receive
• 10 mL graduated cylinder,
• 2 250 mL beakers,
• 1 test tube,
• 1 eye dropper,
• rubber tubing (30cm),
• one-hole rubber stopper

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What factors might influence the reaction rate?

• Temperature
• Strength of Acid or Concentration
• Type of Metal Used
• Surface Area
• Rise to the challenge

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Assignment

• Question What is the effect of _____ on the
  reaction rate of hydrochloric acid and a
  particular metal?
• Hypothesis  (If, then, because)
• Manipulated Variable
• Responding Variable
• Controlled Variables
• Materials         
• Diagram
• Validity Measure (Calibrate? Prevent
  Contamination?)
• Procedure
• (at least 5 levels, repeated at least 2x)

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Suggestions

• Rate vs. Temperature
• Students will need 1 M HCl, water baths,
  thermometers, and heating/cooling equipment.
  Mossy Zn is the best metal for this experiment.
• Rate vs. Concentration
• Students will dilute 1 M HCl with distilled
  water.
• Mossy Zn or Mg ribbon work best for this
  experiment.
• Rate vs. Surface Area
• Students will need 6 M HCl for this experiment or
  else the oxide coating on the foil will not
  decompose fast enough for students to get useful
  data in class. Use Al foil pieces that are no
  bigger than 2cm square.
• Rate vs. Type of Metal
• Students will need 1 M HCl and access to Mg, Zn,
  Fe, Al, Cu and Sn. Size/mass of metal is a
  controlled variable that students frequently
  neglect to include in their experimental designs.

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Experimental Controls?

• Amount of Acid?
• Strength of acid?
• Amount of Metal?
• When will you stop the trial?