High School Biology-Chemistyr SMILE Meeting
27 January 2004
Notes Prepared by Porter Johnson

Patricia Riley [Lincoln Park HS, Chemistry]        Types of Chemical Reactions
Pat set the objectives as (1) performing reactions and recording observations, and (2) identifying reaction types from observations.  She provided us with the following materials, and we worked in groups of 4:

Candle   Beaker Magnesium Metal Strip: Mg
Test tubes Steel wool Hydrogen Chloride Solution: HCl
Sodium Chloride: NaCl Matches  Hydrogen Peroxide Solution: H2O2  
Copper Metal strip: Cu   Wood splints Silver Nitrate Solution:  AgN03
Lump of sulfur: S8   Manganese (II) Dioxide: MnO2   
    Procedure [Precaution: wear eye protection when doing these experiments under the supervisiou of a knowledgable person]:
  1. Take a Candle. Record observations. Now, ignite the candle with a match. Record more observations. Hold beaker upside down over the flame for about 30 seconds. Record observation. Finally, extinguish the candle.
  2. Use the steel wool to shine up the copper metal strip.  Use a paper towel to wipe the copper strip clean.  Study the lump of sulfur and the clean copper strip and record your observations.  Now rub the clean copper strip with the lump of sulfur, and record your observations.
  3. Study the hydrogen chloride solution and the magnesium metal and record your observations.  Place 20 drops of hydrogen chloride into a clean test tube.  Drop ONE (1) small piece of magnesium metal into the test tube and record all observations. Wash out the test tube with lots of water.
  4. Study the silver nitrate and sodium chloride solutions.  Record your observations.  Place 20 drops of silver nitrate and 20 drops of sodium chloride into a clean test tube, and swirl the test tube to mix.  Record all your observations and then rinse out the test tube with lots of water.
  5. Study the hydrogen peroxide and manganese (II) dioxide and record your observations. Place 20 drops of hydrogen peroxide into a clean, dry test tube. Using a wooden splint, add a few grains of manganese (II) dioxide to the test tube. Record all your observations, and then rinse out the test tube with lots of water.
    Observations and Commentary:
  1. Combustion:  2CH2 + 3 O2 ® 2H20 + 2 CO2. Note that water is produced and condenses as a fog inside the beaker.
  2. Synthesis: Cu + S ® Cu S.  Note that the copper turns dark where the sulfur is rubbed against it, since CuS  [copper sulfide] is produced 
  3. Single Displacement: Mg + 2 HCl ® MgCl2 + H2.  Bubbles are formed in the test tube, since hydrogen is produced.
  4. Double Displacement: AgN03 + NaCl ® NaNO3 + AgCl.  The NaNO3 [sodium nitrate] is produced and remains in solution, whereas the insoluble AgCl: silver chloride forms as a white precipitate.
  5. Decomposition: 2H2O2 ® 2H20 + O2.  Note that MnO2 [manganese dioxide] serves as a catalyst for the reaction, but does not itself change.  Bubbles indicate that oxygen gas is produced.
Beautiful Phenomenological Chemistry! Excellent, Pat!

Therese Donatello  [Edwards School]         Atomic Structure:  Don't use just the Bohr Model anymore!
Terry used the LAB-AIDS INC [http://www.lab-aids.com] kit Sublevel Orbitals of the Atom (Quantum Models) [https://lab-aids.com/kits-and-modules/details/sublevel-orbitals-of-the-atom-models-quantum-models] to represent electronic orbitals that correspond to specific energy levels and sub-levels in atoms.  The following summary is given at the website listed above:

"3-dimensional model which clearly shows the position and number of electrons along the x, y and z axes as well as the orbitals of the sublevels of the major energy levels. As the students assemble the model, they will review the four quantum numbers and Pauli’s Exclusion Principle. They will identify the number and position of electrons in various atoms. Using specially designed components which simplify a rather abstract concept, students are able to observe the three dimensional effect of the model. A quantum numbers information chart is provided on each worksheet making it easier for the student to assemble the model starting with the s1 orbitals. Color-coded components help distinguish the differences between S and p orbitals. Students construct models of several common elements in the lab exercise. The models reinforce how the properties of a family of elements on the Periodic Table are a reflection of similarities in the electron configuration of their atoms."
Terry used this kit to make Tinker Toy® models of various atoms, showing the geometry of the electrons in the various energy levels.  For example, the 1S orbital, is represented as a small, clear-blue plastic disk, and the single electron in hydrogen is represented as a black dot on that orbital disk.  Helium, which contains 2 electrons in the 1S orbital, contains two black dots on a single blue orbital disk.  Beryllium, containing 4 electrons, has a 1S orbital, as well as a 2S orbital, represented by a larger red disk.  Each disk contains two black dots, representing two electrons in this orbital.  Carbon, containing 6 electrons, has the 1S and 2S orbitals (blue and red disks, as before), as well as three "figure eights" made out of clear green, yellow, and pink plastic, representing the 2P orbitals; 2Px 2Py 2Pz.  Two dots, representing the two electrons in the 2P state of carbon, are placed somewhere on the 2P orbitals.

The structure of the periodic table was greatly clarified with these models.  In a given row of the periodic table, orbitals are being filled until they contain the maximum number of electrons allowed by the Pauli Exclusion Principle.

Very thought-provoking! Thanks, Terry.

Notes taken by Benjamin Stark