Chem Lab 2005 Science Olympiad Coaches Clinic

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Chem Lab 2005Science Olympiad Coaches Clinic

• Patti Smith, National Event Supervisor
• Judy Day, Teachers Teaching with Technology
• Mike Osborne, Texas Instruments
• pattismith_at_direcway.com

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What do they need to be able to do every year?

• interpretation of experimental data (tabular
  and/or graphic)
• observation of an experiment set up and running
• computer or calculator sensors/probes
• stoichiometry mole conversions and percentage
  yield

• Nomenclature and formula writing - symbols and
  charges for the following ions by memory
  nitrate, carbonate, phosphate, acetate, sulfate,
  ammonium, bicarbonate, and hydroxide (ite forms
  of ates listed)

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How to prepare participants

• Make sure students read the directions and pay
  particular attention to the the description of
  the event (The Competition)

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How to prepare participants

• Have them do many experiments together
• Have them determine their individual strengths
• Divide (and conquer) tasks during competition
• Check each others work

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How to prepare participants

• Get as many lab books from your chemistry teacher
  as possible have students explore labs by topic
  and do the ones that appear consistently

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Thermodynamics - Topics

• direction of heat flow and phase diagrams
• endothermic and exothermic processes
• units of heat measurement
• heat capacity
• calorimetry
• Heat of . and associated calculations
• State or National level Gibbs free energy and
  entropy

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Direction of heat flow and phase diagrams

• (Energy accompanies all reactions)

Endothermic reactions require energy to form
products (?H is positive)
Exothermic reactions release energy as a product
(?H is negative)
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Phase Diagram

• 1 solid warming up
• 2 solid melting
• 3 liquid warming up
• 4 liquid vaporizing
• 5 gas warming up

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Heat in Changes of State

• 1 specific heat of solid
• 2 heat of fusion
• 3 specific heat of liquid
• 4 heat of vaporization
• 5 specific heat of gas

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Cooling curve

• Same process as a heating curve only the energy
  is released!

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Endothermic and exothermic processes

• Endothermic
• Melting
• Vaporizing
• Chemical reactions that have a positive ?H
  (absorb energy)

• Exothermic
• Freezing
• Condensing
• Combustion
• Chemical reactions that have a negative
  ?H(release energy)

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Thermodynamics - sample activities/labs

• ? Determine specific heat of metal (coffee cup
  calorimeter)
• ? ?H of a reaction (e.g., acid/base or any
  endothermic or exothermic reaction)
• ? Determine specific heat of liquid
• ? Experiment based on heat exchange between water
  samples
• Heat of fusion of ice
• At the State or National level Hesss Law
  Applications (calculations and experiments)

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Heat of . and associated calculations
Determine the thermal energy released when 50.0
grams of methane is burned in excess oxygen. CH4
(g) 2 O2(g) CO2(g) 2 H2O(g) 890.32
kJ ?H -890.32 kJ / mol CH4, so 50.0 g CH4
1 mol CH4 -890.32kJ
-2.78
x 103kJ 16.0 g CH4 1 mol
CH4
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Heat of . and associated calculations
Determine the mass of of water (at its freezing
point) that can be melted with 9.00 kJ of thermal
energy. H2O(g) 6.02 kJ H2O(l) ?H
6.02 kJ / mol H2O so 9.00 kJ 1 mol H2O
18.0 g H2O
26.9 g H2O
6.02 kJ 1 mol H2O
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Hesss Law and associated calculationshttp//www.
saskschools.ca/curr_content/chem30/modules/module3
/lesson5/lesson5.htmltop

• Find the enthalpy change for the following rx
• 2P(s) 5 Cl2(g) 2 PCl5(s)
• using the following thermochemical equations
• PCl5(s) PCl3(s) Cl2(g) ?H 87.9 kJ
• 2 P(s) 3 Cl2(g) 2 PCl3(s) ?H -574 kJ
• Rearrange reaction 1 2 so that their sum will
  equal
• 2P(s) 5 Cl2(g) 2 PCl5(s)
• (See next slide)

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Hesss Law and associated calculations

• Reverse and double reaction 1 (product will be 2
  moles of PCl5(s) and ?H will be negative and
  doubled) and add
• 2 PCl3(s) 2 Cl2(g) 2 PCl5(s) ?H
  -175.8 kJ
• 2 P(s) 3 Cl2(g) 2 PCl3(s) ?H
  -574 kJ
• Sum 2P(s) 5 Cl2(g) 2 PCl5(s)
• ? for this reaction is the sum of the ?Hs
• -175.8 kJ (-574 kJ) -749.8 kJ
• 2P(s) 5 Cl2(g) 2 PCl5(s) ?H -749.8 kJ

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Gibbs Free Energy Equation

• ?G ?H T?S
• G is the free energy while H is the enthalpy and
  S is the entropy. ? means change
• Reactions tend to proceed in such a way as to
  maximize randomness(entropy) and minimize energy
  (enthalpy).
• Reactions are spontaneous if ?G is negative

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Physical Properties - Topics

• density
• color
• conductivity
• boiling melting points
• electrical resistance
• elasticity / brittle, not brittle
• malleability

• heat capacity
• specific heat
• solubility
• Magnetism
• Electrical resistance
• extensive (amount of matter) intensive (type of
  matter) properties

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Physical Properties - sample activities/labs

• ? Determine the density of a substance (solid or
  liquid)
• ? Use density to identify an unknown metal
• ? Determine the elasticity of a solid using
  Hookes Law
• ? Separate a mixture by physical properties
  (magnetism, solubility, etc.)
• ? Explore the effect of temperature on solubility

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Density

• D m/v, where mmass of the object and v volume
  of the object.
• Volume of a regular shaped object vs. volume of
  an irregular shaped object

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Determine the elasticity of a solid using Hookes
Law
Hooke's law F - k X Where X measures the
displacement of the mass from an equilibrium
position k is a constant characteristic of the
particular spring known as spring constant. (The
spring constant has units of force per unit
length. ) This force law is known as Hooke's law.
http//webphysics.ph.msstate.edu/javamirror/ntnuja
va/springForce/springForce.html
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Separate a mixture by physical properties

• Magnetism
• Solubility
• Paper chromatography
• Distillation

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Effect of Temperature on Solubility
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Websites

• Stoichiometry Sig Figs http//dbhs.wvusd.k12.ca
  .us/webdocs/ChemTeamIndex.html

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WebsitesTI Activities exchange
http//education.ti.com/educationportal/activityex
change/ActivitySearch.do?cidus
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WebsitesVernier

• http//www.vernier.com/chemistry/

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Websites Thermodynamics

• Thermodynamics (multiple links)
  http//www.chemistrycoach.com/tutorials-7.htmTher
  modynamics
• Change of State http//www.chem4kids.com/files/m
  atter_states.html
• Hesss Law http//dbhs.wvusd.k12.ca.us/webdocs/Th
  ermochem/HessLawIntro1.html
• General Chemistry http//ull.chemistry.uakron.edu
  /GenChem/06/

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Websites Thermodynamics

• Hesss Law http//ull.chemistry.uakron.edu/GenChe
  m/06/
• Enthalpy http//ull.chemistry.uakron.edu/GenChem/
  06/
• Coffee cup calorimeter http//chemistry.allinfoab
  out.com/features/calorimeters.html
• Calorimetry http//www.chem.latech.edu/deddy/che
  m104/L5Calorie.htm

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WebsitesPhysical Properties

• http//www.chem.tamu.edu/class/majors/tutorialnote
  files/intext.htm
• http//antoine.frostburg.edu/chem/senese/101/matte
  r/faq/extensive-intensive.shtml
• quiz http//antoine.frostburg.edu/chem/senese/101
  /matter/classify-properties-quiz.shtml
• http//www.foundationcoalition.org/home/sophomore/
  property.ht

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Hookes Law

• http//asms.k12.ar.us/classes/physics/GENERAL/KENN
  ETH/HOOKE.HTM
• http//hyperphysics.phy-astr.gsu.edu/hbase/permot2
  .html
• http//en.wikipedia.org/wiki/Hooke's_law
• http//webphysics.davidson.edu/Applets/animator4/d
  emo_hook.html

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EasyTemp Activity (Groups of 2-3)

• Endothermic Exothermic Reactions

Select units, type of graph