Chemistry Signs Students must be supervised during any laboratory event practice. In all lab events, each team member must wear goggles for eye protection and an apron or lab coat. In the lab rooms, shoes must be worn that do not have open spaces and cover the entire foot; sandals and open-toe shoes are not acceptable.
There are two competitive tracks:
Chemistry Signs A poster is submitted on the theme: "Chemistry of Toys".
Each team at each level (Level I and Level II) submits a poster based on the topic "Chemistry of Toys." The poster must be two-dimensional and the original creation of a chemistry student or group of students in the team's school at the same level of chemistry as the team. The display should be on one side of a single sheet of cardboard or poster board whose dimensions are within two centimeters of 56 cm x 71 cm, labeled on the back with the school name and "Level I" or "Level II".
The event prize will go to the poster representing the most original, memorable, effective, attention-getting, and generally appropriate message.
Threaded Ions The purpose is to grow the most nearly perfect crystal.
The team will submit a single crystal of potassium aluminum sulfate (KAl(SO4)2.12H2O), sodium aluminum sulfate (NaAl(SO4)2.12H2O), or ammonium aluminum sulfate (NH4Al(SO4)2.12H2O). The crystal must be grown on one piece of the official thread. If a seed crystal is used, it must not be bigger than 4 mm in its longest dimension. The crystal thread should be taped to a 3 x 5 inch file card, labeled with the school name and "Level I" or "Level II" and placed in a clear plastic bag such as a plastic sandwich bag.
You may be able to find the compound (potassium, sodium, or ammonium alum) in the spice section of a grocery store. Hints for growing crystals may be found in various books; one that may be in your school or public library is Crystals and Crystal Growing by Alan Holden and Phylis Morrison, 1982, MIT Press. One suggestion that has worked for some is to refrigerate the solution to slow down crystallization.
The crystal will be judged on the following basis:
Note: a single crystal only--not cluster crystals. A small, better formed and perfectly transparent crystal might well receive more points than a large, very cloudy one. Each team at each level (I and II) may enter one crystal prepared by any student at the school who is at the same level of chemistry as the team.
A maximum of three team members may participate in each event. Also see other events for both Level I and Level II teams listed at the end.
A variety of equations will be completed and balanced and types of chemical reactions will be identified by each team.
None, except for any desired practice.
Given reactants either by names or formulas, and sometimes products, each team will be challenged to write within 30 minutes a number of balanced equations. The balancing method(s) can be freely selected by the team--only the results matter. The teams will also be asked to identify some of the equations by reaction type (for example: single replacement, double replacement, composition/synthesis, decomposition, combustion, neutralization). A list of possible reaction types will be provided. Notes are not allowed.
The team with the greatest number of correct, complete, and balanced equations, and correct identifications will be declared the winner.
Concurrent event is Weighing by Redox.
Hydronium Hijinks The concentration of a strong, monoprotic acid solution provided at the event will be determined.
Prior to the Chemathon, the team (with teacher supervision) must prepare 500 mL of approximately 0.1 M sodium hydroxide solution, NaOH(aq). The actual concentration of the basic solution should then be determined (to the nearest 0.001 M or better). This can be accomplished by titrating the base against an acid solution of accurately known concentration, or by titrating the base against a primary standard, a solid acidic substance of known purity and high molar mass. The NaOH solution must be made up and standardized by the team; it cannot be a commercial solution.
Using their own standardized basic solution and their own 50-mL burets, team members will determine the concentration (mol/L) of the acid solution provided at the event. Four burets (supplied by the team) will be used: one will be set up by the team to deliver the initial volume of unknown acid solution, the other three burets will be filled with standardized base by the team so that all three team members can conduct independent titrations. As many titrations as desired can be completed with in the 30-minute time limit, recognizing that only 200 mL of the unknown acid solution will be available to the team. No electronic pipets or burets may be used. Notes on calculations or procedures, etc., are not allowed; however, the container of sodium hydroxide solution may be labeled with the concentration.
The team will report only one acid concentration value, in mol/L with an appropriate number of significant digits, for judging. Supporting data and calculations must be provided. The unknown acid solution's concentration will be between 0.05 M and 0.15 M. The team must bring to the Chemathon four 50-mL burets and its standardized sodium hydroxide solution. Other needed supplies will be provided at the event.
The team reporting the mol/L value for the acid solution closest to the "known" value will be declared winner.
Concurrent event is Mendeleev Madness.
Mendeleev Madness Questions based on the periodic chart will be fielded by the team.
None, but a periodic table review might be appropriate. For practice, the team might want to play the following on-line "Element Games":
Each team will be given a blank periodic table and a written set of clues regarding the physical or chemical properties of the first 26 Group A elements of the periodic table. (Examples: an atom of element R contains 11 protons. Element X has a lower ionization energy than element D.) Team members will be given 30 minutes to decide on the locations of all coded elements on the blank periodic table. Notes are not allowed; only a pencil or pen is to be brought to the event. One copy of the filled-in periodic table is submitted by the team for judging. All materials must be returned when time is called.
The team's periodic table with the largest number of coded elements correctly placed will be judged the winner.
Concurrent event is Hydronium Hijinks.
Weighing by RedoxThe mass of a pre-cut sample of magnesium metal is calculated from data obtained when excess hydrochloric acid is added to the sample, and the volume of wet hydrogen gas is measured at known temperature and pressure.
None, except for practice. Locate and test a suitable gas-collecting tube.
The team will be given a length of magnesium metal. A 20-mL sample of 2 M hydrochloric acid is poured into an inverted gas-measuring tube; the tube is then filled with distilled water. The magnesium metal sample is held in position near the mouth of the tube with a length of thin copper wire, which is held in place with a one-hole stopper. The tube is then inverted into a partially-filled beaker of water. The hydrogen gas generated is collected by water displacement. From gas law calculations, taking water vapor pressure and the difference in water levels into account, the team calculates the original mass of magnesium metal in the sample, expressed to suitable precision. Supporting data and calculations must be submitted. Hint: it will not be possible to equalize the water levels; the mass of magnesium in the sample will produce between 25 and 45 mL of wet hydrogen gas.
The magnesium sample, hydrochloric acid, distilled water, beaker, ring stand, and a ruler will be provided. The current value of the atmospheric pressure will also be provided, as well as a printed sheet with necessary values (R = 8.3145 dm3 kPa/K mol = 0.082058 L atm/K mol, M(Mg) = 24.3050 g/mol, and a table of water vapor pressures in kPa and mmHg at various temperatures). The team must supply its own gas-collecting tube, thermometer, copper wire, a suitably sized one-hole stopper, and a nonprogrammable calculator. The team may not bring notes for the calculations.
The team reporting the mass of magnesium with the lowest percent error (judged by its previously measured mass) will be declared winner.
Concurrent event is Reactions in Action.
Viscoelastic Bounce This is a competition involving homemade "silly putty."
The team should practice making elastic balls with a recipe similar to the following, using ingredients available in stores: Place a mixture of 25 mL white glue (such as Elmer's) and 20 mL water in a small paper cup or plastic Ziploc-type bag. (The polymer in white glue is polyvinylacetate.) Add 5 mL of a saturated solution of borax (sodium tetraborate), about one level tablespoon per cup of water, and stir or knead well. The ball may be cured with a hair dryer. The team should investigate the effects of changes in ingredient proportions, ball size, etc.
Team members may prepare any number of balls from materials and supplies they bring with them. The balls must be prepared during the event using the ingredients (white glue, borax, and water) but not necessarily the amounts given above. One or two balls will be dropped individually (two drops in all) from the height of a lab bench (91 cm). The team making the ball that bounces the highest wins.
Concurrent event is Chemical Jeopardy.
A maximum of three team members may participate in each event. Also see other events for both Level I and Level II teams listed at the end.
The Balancing Act A variety of equations will be completed and balanced by each team.
None, beyond any desired practice.
Teams consist of three or fewer students, as at all events. Given reactants either by names or formulas, and sometimes products, each team will be challenged to write within 30 minutes a number of balanced equations. The balancing method(s) can be freely selected by the team--only the results matter. Notes are not allowed. The winning team will be the one with the greatest number of correct, complete, and balanced equations.
Concurrent event is Beat the Clock.
LeChatelier's Lunacy None, beyond any desired practice.
Any required materials except calculators and writing instruments will be provided. The team will solve a series of chemical equilibrium problems using a nonprogrammable calculator. These problems could involve Kc, Kp, Ksp, Ka, or Kb. At least one problem will involve LeChatelier's Principle. The team will turn in its calculations as well as its final answer and both may be used to determine the final rankings.
A draft sample problem is available. For additional practice problems, it is suggested that teams try old AP Chemistry Exam equilibrium free response questions - there are plenty to choose from since there is one every year (it has been Question 1 for the last several years). At the College Board's AP Central website the last several years' exams are available as .pdf documents. You will have to become a registered user if you are not already one, but it is a free service.
Concurrent event is Chemysterie.
Beat the Clock Each team will bring its own iodine clock reaction stock solutions. The team is asked to adjust the solutions during the event so the color change takes place in a specific time--from 15 seconds to 2 minutes.
The iodine clock reaction is based on iodate and meta-bisulfite ions reacting in solution to produce dissolved molecular iodine (I2) which combines with starch indicator to form a deep blue color. The time required for the appearance of the blue starch-iodine complex depends on the concentration of the reactants and the temperature of the system.
The team (with teacher supervision) should prepare stock solutions of the two "iodine clock reaction" reactants--0.02 M potassium iodate (KIO3) and 0.001 M sodium meta-bisulfite (Na2S2O5)/starch suspension--according to the procedure suggested below. The team should also bring a small amount (less than 50 mL) of 1 M sulfuric acid. The other equipment and distilled water required for the event will be provided at the Chemathon. The team should bring its own burets and pipets.
The potassium iodate stock solution can be prepared by dissolving 4.3 g potassium iodate in enough distilled water to make one liter of solution. To prepare the sodium meta-bisulfite/starch stock solution, first make a thin paste by stirring 4 g soluble starch into a small amount of distilled water, add the starch paste to roughly 500 mL of boiling distilled water, and allow the suspension to cool. (As an alternative to soluble starch, you may wish to try either spray starch or starch-based biodegradable packaging "peanuts" dissolved in water.) To the starch suspension, add 0.2 g sodium meta-bisulfite and enough distilled water to bring the total volume to 995 mL. To prepare the solution for use, add 5 mL of 1 M sulfuric acid (with stirring) immediately before conducting the clock reaction, or no more than 24 hours in advance. These stock solutions, if mixed in equal volumes, produce a very fast reaction time. The team (with teacher supervision) should determine the dilutions needed to obtain reasonable clock reaction times. Results are best if the potassium iodate solution is diluted rather than the starch solution. The team should conduct preliminary time trials--see below--in advance of the Chemathon to determine a strategy for adjusting the solutions to yield a pre-specified time interval.
The judge will assign the team a random time from 15 seconds to 2 minutes. The team will have 10 minutes to dilute the concentrations (or adjust temperatures, if desired) of either or both solutions to obtain the specified reaction time. The team may not actually mix the solutions until the official trial begins. When the team is ready (within the 10-minute time limit) the judge signals "start." At that time, the team must pour the solutions together into a 250-mL beaker on a magnetic stirrer, and the official time for the reaction (when the first blue color appears) is noted. Each team may complete up to three trials. The trial time closest to the specified time will be the team's official event result.
The team achieving the reaction time closest to the requested time will be declared the winner.
Concurrent event is The Balancing Act.
Make My [Fara]day Using electrolysis, each team will plate out a specified mass of metal using Faraday's law to determine the amount of time needed to carry out this process.
The team will need to bring about 300 mL of a 1 M CuSO4 solution (the addition of about 1 mL of 6 M sulfuric acid to this solution may improve the adhesion of the plated copper). The team will also need to bring 2 copper electrodes suitably marked as cathode and anode, a six-volt battery, a 0-5 A ammeter, a variable resistor, 4 insulated wire leads, and 8 alligator clips. Beakers (250 mL) will be provided.
Team members will use an electrolysis cell consisting of a copper anode, a copper cathode, and 1 M CuSO4 in a 250-mL beaker to plate out an assigned mass of copper onto the cathode. Notes on calculations or procedures, etc., are not allowed. The judge will pre-mass the cathode and assign a mass, between 0.20 g and 1.00 g, to plate onto it. The power source will be a 6 V lantern battery (preferably one that has not been stored for a long time or used much) and the circuit will also contain an ammeter to measure the current flow. The current can be controlled with a variable resistor, or by adjusting the separation of the electrodes. The students should select a current of no more than 2.5 A and using Faraday's law, calculate the time needed to plate out the specified mass of copper. The distance between the electrodes may be varied to control resistance, but the electrodes must remain in the 250-mL beaker provided. The electrolysis should be carried out to verify the calculations. The judge will mass the final cathode. The team score will depend on the lowest percent error after one continuous run.
Concurrent event is Avogadro's Tiebreaker.
Traveling Electrons The team will use an oxidation-reduction titration to determine the percent by mass of sodium hypochlorite in chlorine-based liquid laundry bleach provided at the event.
Prior to the Chemathon, the team (with teacher supervision) must prepare 500 mL of approximately 0.1 M sodium thiosulfate solution, Na2S2O3(aq). The actual concentration of the solution should then be determined (to the nearest 0.001 M or better). This can be accomplished either by dissolving a known mass of Na2S2O3.5H2O (248.19 g/mol) in enough distilled water to make 500 mL of solution, using a 500-mL volumetric flask; or else by titrating the solution against a primary standard such as potassium iodate or oxalic acid dihydrate, using the method described below for titrating NaOCl. The second method is more accurate but less convenient.
Using their own standardized sodium thiosulfate solution and their own 50-mL burets, team members will determine the moles of sodium hypochlorite, NaOCl, in weighed samples of the bleach solution provided at the event. The team will supply three burets which they can fill with the standardized sodium thiosulfate solution so that all three team members can conduct independent titrations. As many titrations as desired may be completed within the 30-minute time limit. No electronic pipets or burets may be used. Notes on calculations or procedures, etc., are not allowed; however, the container of sodium thiosulfate solution may be labeled with the concentration.
The team will report only one value of the percent of sodium hypochlorite, with an appropriate number of significant digits, for judging. Supporting data and calculations must be provided. The unknown percent by mass of NaOCl will be between about 5 and 6 percent. The team must bring to the Chemathon three 50-mL burets and its standardized sodium thiosulfate solution. Other glassware and supplies will be provided at the event.
Liquid laundry bleach such as Chlorox brand bleach is an aqueous solution of sodium hypochlorite, NaOCl. The unknown bleach will be available in plastic dispensers. The suggested titration procedure is as follows. A 250-mL Erlenmeyer flask is rinsed, dried on the outside, and weighed to the nearest milligram. A 2.0-2.5 mL bleach sample is dispensed into the flask, which is then reweighed to determine the sample mass. About 100 mL distilled water is poured down the inside wall of the flask to dilute the bleach. Then 10 mL 6 M acetic acid and 8 mL 2 M KI is added. The NaOCl oxidizes the iodide ion to molecular iodine:
2I- + OCl- + 2H+ --> I2 + Cl- + H2O
The molecular iodine is then promptly titrated with the standard sodium thiosulfate solution:
I2 + 2S2O32- --> 2I- + S4O62-
When the solution has changed to a gold-orange and then to a faint yellow color, twenty drops (1 mL) of starch indicator are added to produce the deep blue color of the starch-iodine complex. (By not adding the starch until near the end point, the progress of the titration can be followed by the fading of the yellow color of the molecular iodine.) The end point is reached when the blue color vanishes with the addition of one final drop of titrant. From the mass of the sample and the moles of NaOCl in it, the percent by mass of NaOCl is calculated.
The team reporting the percent mass value closest to the "known" value will be declared winner.
Concurrent event is Chemical Jeopardy.
A maximum of three members of each team (Level I or Level II) may participate in each event.
Avogadro's Tiebreaker None.
All materials except calculators and writing instruments will be provided. The team will solve a chemical problem using a nonprogrammable calculator and possibly one or more of the following: ruler; periodic table; buret, pipet, balance, graduated cylinder, and similar apparatus. The team will turn in its calculations as well as its final answer and both will be used to determine the winner. This event will be used as a tie breaker only in case of a tie. It is very important to enter this event, because a team that does not will forfeit any tie.
Look here for an example of tiebreaker questions used in the past.
Concurrent events are Chemysterie (Level I) and Make My [Fara]day (Level II).
Chemical Jeopardy The team will answer questions in the form of answers.
None.
This game is patterned after the TV game show, JEOPARDY. Unlike the TV JEOPARDY, there will be no daily double; however, there will be a FINAL JEOPARDY question when a team can risk any amount of its score in answering the FINAL JEOPARDY question. Points will be awarded for correct answers and subtracted for wrong answers according to the level of difficulty of each question. As in the TV game, this will be a fast-paced event. Therefore quick and accurate recall and a bit of daring will determine the final winner. The team with the highest point total after FINAL JEOPARDY will be declared the event winner. As in the TV game, all answers must be given in "the form of a question."
For example Question: This English Quaker School teacher is sometimes known as the "Father of the Atomic Theory." Response: Who is John Dalton? Some, but not all, of the categories for questions may be: famous chemists, the elements, nomenclature, laboratory operations, and laws and theories.
The framework for Jeopardy is available as an open source project for download.
No visitors are allowed at this event.
Concurrent events are Viscoelastic Bounce (Level I) and Traveling Electrons (Level II).
Chemysterie The identity of between six and eight unknown solutions, each containing one substance dissolved in water, is determined.
The team should practice making the necessary observations.
Each team will receive between six and eight coded plastic pipets, each containing several milliliters of an aqueous solution of a single unknown substance. Each pipet will contain a different solution. The team will have a maximum of thirty minutes to make observations on the individual solutions, and on drops mixed in pairs, in order to identify the substances. No substances other than the solutions in the pipets may be used.
The possible substances are: HCl, HNO3, H2SO4, NaOH, NH3, and soluble salts containing Ag+, Al3+, Ba2+, Co2+, CO32-, Cu2+, Fe3+, I-, Ni2+, and Pb2+. All salt solutions will be 0.1 molar; NaOH (if present) will be 6 M; NH3, HCl, and H2SO4 (if present) will be 3 molar.
The team will learn at the event which 6-8 substances are actually present. A transparent plastic sheet printed with an 8 x 8 matrix will be provided on which drops of solution should be mixed in pairs. The team must carry out all tests on the plastic sheet provided. Testing the solutions by touching is not allowed.
While the team may take the full thirty minutes, both speed and accuracy count: the results are scored as the square of the number of correct identifications divided by the time to the nearest minute, plus the number of correct identifications. For instance, a team that reports 6 correct answers in 25 minutes will have a score of (62/25) + 6 = (36/25) + 6 = 7.4. The team with the highest score will be declared the winner.
Concurrent events are Avogadro's Tiebreaker (Level I) and LeChatelier's Lunacy (Level II).