Online Chemistry Experiments

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Online Chemistry Experiments

• Venkat Chebolu, Ph. D.
• Associate Professor of Chemistry
• Jefferson Community College
• Watertown, NY 13601

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List of Experiments

• Observations of Chemical Changes
• Laboratory Techniques and Measurements
• Separation of a Mixture of Solids
• Properties of Gases
• Liquids and Solids
• Physical and Chemical Properties
• Ionic Reactions

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List of Experiments (contd.)

• Stoichiometry of a Precipitation Reaction
• Caloric Content of Food
• Determination of Water Hardness
• Le Chateliers Principle

4
Observations of Chemical Changes

• NaHCO3 HCl
• HCl Bromothymol Blue (BTB)
• NH3 BTB
• NaOCl KI observe and test with starch
• KI Pb(NO3)2
• NaOH Phenolphthalein
• HCl Phenolphthalein
• CuSO4 NH3

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Laboratory Techniques and Measurements

• Length of various objects
• Temperature of boiling water and ice-water
  mixture
• Volume of water in a graduated cylinder
• Number of drops of water from a micropipet in 1
  mL (graduated cylinder)
• Mass measured to 0.1g on a digital scale
• Density of liquids and solutions

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Laboratory Techniques and Measurements (contd.)

• Density of Solid by Water Displacement
• Density of Solid by Archimedes Principle

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Separation of a Mixture of Solids

• Mixture of Iron Filings, Sand, Benzoic Acid and
  Salt
• Iron filings separated by using a magnet
• Sand separated by dissolving the Benzoic Acid and
  salt in hot water
• Benzoic Acid separated by cooling in an ice-bath
  and filtration of resulting crystals
• Salt isolated by evaporation of salt solution
  (filtrate) at room temperature

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Properties of Gases

• Gas is collected by displacement of water in a
  pipet bulb.
• H2 is generated by reacting (1)Zn and (2)Mg with
  HCl.
• O2 is generated from H2O2 and MnO2
• CO2 is generated from NaHCO3 and HCl
• H2 is tested by blowing it over a lit match

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Properties of Gases (contd.)

• O2 is tested by inserting a lit toothpick into
  the pipet bulb
• Mixture of H2 and O2 collected in a pipet bulb is
  tested with a lit match as well
• CO2 is tested with lime water and with BTB and
  with a lit toothpick
• Gas evolved when Alka-Seltzer is dissolved in
  water is tested just like CO2

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Liquids and Solids

• B.P. of isopropyl alcohol is determined by
  inverting a closed-end capillary tube into 1 ml
  of the alcohol in a test tube.
• M.P. of acetamide is determined by filling a
  closed-end capillary tube with the solid and
  noting the temperature of the water bath when the
  solid melts.

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Physical and Chemical Properties

• Substances tested include Mg, Cu, Zn, MgO, CuCO3,
  Cu(NO3)2 and NaCl
• Tests include
• Color
• Odor
• Effect of heating in a test tube
• Solubility in Cold and Hot water, and litmus test
• Reaction with dilute HCl
• Reaction with dilute NaOH

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Ionic Reactions

• In plate wells, each of the aqueous solutions of
  Co(NO3)2, Cu(NO3)2, Fe(NO3)2, Ba(NO3)2, and
  Ni(NO3)2 are reacted separately with solutions of
  Na3PO4, NaHCO3, NaI, Na2SO4, NaCl, Na2CO3 and
  NaOH
• Evidence of Chemical reaction is to be noted
• Net ionic equations to be written for chemical
  reactions occurring

13
Stoichiometry of a Precipitation Reaction

• Aqueous solutions of Na2CO3 and CaCl2.2H2O in a
  11 molar ratio are reacted and the resulting
  precipitate of CaCO3 is collected quantitatively.

14
Caloric Content of Food

• Food items such as Marshmallow, Peanut, Popcorn,
  Potato chip and Walnut are burnt, and the heat
  generated is used to heat a known mass of water
  in a beaker
• Heat generated per gram of each item burnt is
  calculated

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Determination of Water Hardness

• Calmagite indicator is used to detect presence
  (red) or absence (blue) of Ca2 and Mg2 in water
  samples.
• In a plate well, calmagite is added to water
  samples of known and unknown hardness. The number
  of drops of EDTA needed to turn the solution blue
  in each case is determined.

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Le Chateliers Principle

• Mg(OH)2 ? Mg2 2 OH-1
• In a plate well, an aqueous solution of MgCl2, to
  which phenolphthalein is added, is treated with
  an aqueous solution of NaOH till the solution
  turns pink. Then, HCl is added till the solution
  turns colorless.
• A part of this solution is sucked into a pipet
  bulb and held in cold and hot water to see how
  temperature affects this equilibrium.

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Le Chateliers Principle (contd.)

• HSO4-1 H2O ? H3O SO42-
• Thymol blue is used as an indicator to decide
  where the equilibrium lies.
• Na2SO4 and NaHSO4 are added successively to an
  aqueous solution of NaHSO4 to determine direction
  of equilibrium shift.
• This solution is placed in a pipet bulb and
  placed in hot and cold water baths to determine
  the effect of temperature on this equilibrium

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Differences

• Filter funnel supported in a paper cup placed in
  a coffee cup
• Rubber policeman at the end of the glass rod to
  wash down precipitates stuck to the walls of the
  containers not used
• Cutting, bending and drawing glass experiment not
  being performed online.
• Bunsen Burner and Fisher burner experience missing

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Differences (contd.)

• Inserting glass tubing into tygon tubing is not
  experienced online
• No experience using a triple beam balance
• Spectroline pipet filler not used online
• No experience with coffee cup calorimetry
• No sublimation of Naphthalene online
• No experience with simple distillation

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Differences (contd.)

• No experience with vacuum (Buchner funnel)
  filtration
• No experience with gravimetric experiments using
  crucibles and crucible tongs and heating to
  constant mass
• Charles law verification experiment not done
  online
• Determining solubility of a salt in water and
  determining whether a solution conducts
  electricity

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Differences (contd.)

• Factors affecting reaction rates lab is not done
  online
• Mg is dropped into different strong and weak
  acids of the same concentration
• Zn, Mg and Cu are dropped into solutions of HCl
• Iodine clock reaction rate is studied as a
  function of reactant concentrations
• Crushed and uncrushed marble is reacted
  separately with HCl
• Zn is added to HCl at different temperatures

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Differences (contd.)

• In F2F setting, there is a three hour time limit
  for the lab. Some students do feel pressured to
  complete the lab in that time or to come back
  later to complete the lab.
• In the online format, there is really no time
  limit and everyone works at their own pace
  resulting in observations such as the
  following
• An unidentified aroma was evident during the
  entire separation experiment. The benzoic acid
  crystal formations seemed quite intriguing that
  resembled pieces of cut fiberglass or MSG. Very
  reflective and lustrous, but seemed to attach
  itself to other substances pretty easily. Salt
  crystal formation gathered to several clumps
  instead of an even formation at the cups bottom.

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Differences (contd.)

• In the F2F situation writing a lab report
  usually entails filling in the blanks or boxes in
  a pre-organized lab format that accompanies each
  lab followed by answering post laboratory
  questions. A lot of the answers received are very
  similar as they are provided after consultation
  with class peers.
• In the online format, the lab write-up is
  expected to include Title, Purpose, Procedure,
  Data Tables, Observations, Questions and
  Conclusions. The organization of the Data Tables
  and Observations is for the most part left for
  the students to figure out.

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Differences (contd.)

• In the F2F situation, when a single answer is
  proposed for a question, that answer is usually
  embraced by the rest of the class and no more
  thinking occurs without intervention.
• In the online mode, everyone is thinking on their
  own until they find some answer to the question.
  This results in a diversity of answers as
  evidenced by the following example.

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Differences (contd.)

• Answers provided for why the boiling point of
  water observed is different from 1000C
• My water boiled at the expected temperature -
  perhaps this is an experimental error on my
  behalf
• The material of the pan that I boiled the water
  in may have had an effect on the boiling point of
  water. Also, the thermometer could be a little
  off
• The water boiled at a different temperature
  because the water was in a smaller container and
  the heat was directly applied

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Observations

• No instructor intervention after experiment is
  started.
• Students are forced to get creative.
• When graded lab report is returned, students
  understanding of the situation is much better
  because they have invested their best thinking
  into the problem.
• A sense of discovery takes hold of the students,
  especially when they seemed to have followed the
  procedure and what they see is different from
  what they expect.

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Observations (contd.)

• Repeating a lab after they have messed up is very
  rarely possible.
• Through these labs students are certainly getting
  a very good hands on experience in manipulating
  chemicals and honing their observation skills.
  This is very similar to the experience a student
  gets in a face-to-face lab course.

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Student Reactions

• While performing this (Ionic reactions lab) I
  learned how to recognize ionic reactions and see
  when they can occur by mixing different
  substances. I enjoyed performing this experiment
  and my confidence of working in the laboratory
  has improved

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Student Reactions (contd.)

• This lab demonstrates that there are many
  different ways to detect ionic reactions. These
  reactions become visible to the chemist as a
  color change, precipitate, or release of gas. It
  is very interesting to note how the exchange of
  positive and negative ions in two reacting
  solutions will change the solubility of a
  chemical and form a precipitate

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Student Reactions (contd.)

• I found this (Caloric Content of Food) lab to be
  very interesting. I never knew it was possible to
  determine the energy content of a food item by
  burning it until I completed this experiment.
  Although I did find that particularly the
  marshmallow in this experiment lit on fire
  quickly and in a matter of seconds the flame
  became a bit out of control, so just a fore
  warning to those who have not completed the lab
  yet.

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Student Reactions (contd.)

• This lab (Caloric Content of Food) has taught the
  process of finding the energy content of food by
  burning a portion of a certain food and taking
  the heat given off by the food and adding it to a
  known mass of water. My observations have also
  taught me that a longer burning food will
  probably lead to a higher caloric food, based on
  the peanut burning longer than the marshmallow.

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Student Reactions (contd.)

• I found this (Water hardness) experiment very
  interesting. I especially enjoyed the fact that
  this is chemistry that I can in fact relate to in
  my every day life. Every one needs water to
  survive. I did find it quite awkward to stir the
  solution with a toothpick. However, in
  determining the water hardness of my local water
  it has made me consider the possibility of
  investing in a water softener. I am confident in
  my skills now and know that if I desire I can now
  test the local water supply wherever I go.

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Student Reactions (contd.)

• This lab (Water hardness) was very interesting.
  The water in the area where I tested has always
  been a concern of mine. For me it was and still
  is very hard to get used to, the quality
  affecting everything from my food to my shower.
  In passing I have heard others say that water was
  hard but it was nice to actually test it and have
  proof of how hard the water actually was.

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Conclusion

• The kit is certainly helping students get the
  kind of hands-on experience that a F2F Chemistry
  lab provides. While certainly not providing each
  and every technique, these experiments go a long
  way in providing a medium for the students to get
  a first hand experience of learning Chemistry by
  doing. Further, it does provide a medium for
  students to think about the experiment they are
  performing and draw conclusions as in a regular
  brick and mortar Chemistry Lab.

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Acknowledgements

• Ron Krempasky AHS for this opportunity
• Linda Jeschofnig AHS for abstract writing
• Peter Jeschofnig AHS for co-presenting
• Vela Chebolu WHS for Powerpoint Design