Surviving and Thriving in the AP* Chemistry Curriculum, Part 3
Chemistry Teacher and Author
So, you've made it through teaching the new AP Chemistry curriculum. You've overcome the trials and tribulations of the Big Ideas, the Enduring Understandings, the Essential Knowledge, and the Learning Objectives. You pressed on through inquiry labs, particulate diagrams, and Coulombic forces. Depleted by an unusually large number of snow days, you're perhaps scrambling to tie up some loose ends since it's likely been quite a tumultuous year, even for the most experienced. So how can we take stock, remain calm, and set the kids up for success next month?
For many years I have offered my kids a last-minute list of "tiny tips" that I think could serve them well going into the exam. In May, I formalized those lists in 2 blog posts: 1 entitled "50 (tiny) things to remember in the AP chemistry exam," and another entitled "(Another) 50 (tiny) things to remember during the AP chemistry exam." Here, I bring together a selection from those lists that have been refreshed and updated to reflect their relevance to the new curriculum.
A few of these tips are the type of random factoids that occasionally appeared on multiple-choice exams of the past, where perhaps a color or an environmental application was tested for a single point. How relevant that kind of thing will be going forward remains to be seen, but others on the list are more profound reminders of fundamentally important concepts.
I hope that these small memory joggers, which in themselves may not mean much, will serve as potentially useful triggers for students, and as such, could spark inspiration at a crucial, pressurized moment during that vital 3-hour period in May. Good luck!
- The speed of a chemical reaction is not related to the equilibrium position.
- Hydrogen bonding is an INTERmolecular force, not an INTRAmolecular bond.
- Electrolysis is only necessary when a reaction is non-spontaneous with a positive Delta G.
- Le Châtelier's principle is not an explanation in itself. A shift in position to reduce an external stress is, as is an understanding that Q must equal K at equilibrium.
- Periodic trends are not explanations.
- Potassium manganate(VII) and sodium dichromate(VI), when in acid, are common oxidizing agents.
- Wash a buret with the solution that it will be dispensing in the titration, and fill the tip.
- Gases behave ideally when at relatively low pressures and relatively high temperatures.
- Catalysts increase the rate of the forward and the backward reaction.
- Common ions make slightly soluble salts even less soluble.
- Kp expressions include ONLY gas partial pressures.
- "Optimal" buffers (that can absorb acid and base equally well), have pH = pKa.
- Clean up an acid spill with a carbonate, not an equally corrosive, strong base.
- Writing the full electronic configuration of an atom can help to explain differences in ionization energies and the patterns in PES data.
- Transition metal ions are often colored in solution.
- Reduction always takes place at the cathode.
- Fluorine always has an oxidation number of –1.
- The bigger the pKa, the weaker the acid; the bigger the Ka, the stronger the acid.
- When using R = 0.0821 in P V = n R T, pressure must be in atm, temperature in K, and volume in L.
- On the exam, use the FULL atomic masses printed on the periodic table.
- When predicting shape, a double bond counts as only 1 area of electron density.
- It is unlikely that any numerical answer on the AP exam will ever require 10 significant figures!
- Since C and H have a similar electronegativity, hydrocarbons are largely non-polar.
- Polarity in organic molecules helps them to be soluble in water.
- Only the first bond of a double or triple bond is counted in hybridization. The others are pi bonds formed by the overlap of UNhybridized p orbitals.
- Breaking bonds within reactants is an ENDOTHERMIC process.
- Alcohols are soluble because they can H-bond with water, NOT because they have a hydroxide group—they DON'T!
- Ions travel through the salt bridge, not electrons.
- Net ionic equations must balance charge as well as atoms.
- A graph of [ X ]–1 versus time gives a straight line for a second order reaction.
- Bromine and mercury are liquids at room temperature and iodine is a solid.
- Transition metals lose their s electrons first.
- Always use temperature in Kelvin in gas calculations.
- The units of Delta H are usually expressed in kJ, and Delta S usually in J; therefore, they must be converted to a single, common unit, if using them to calculate Delta G.
- Orders of reaction can be fractions.
- Organic amines like methylamine, CH3NH2, are weak bases since the lone pair on the N atom can accept H+.
- Positive Ecell values go with negative Delta G values and very large K values.
- When [ H+ ] in solution is < [ OH– ] the solution is basic (and vice versa).
- The condition for neutrality is [ H+ ] = [ OH– ], not pH = 7.
- Beer's law can only be applied to colored salts.
- In dynamic equilibrium, the forward and backward reactions do not stop, they just occur at the same rate.
- When considering macro changes in entropy, look at how the number of gas moles changes.
- Oxygen relights a glowing splint.
- Equilibrium constants are constant at constant temperature.
- Ionic solids have strong ionic bonds that are electrostatic (Coulomb's law), and as a result, have high melting and boiling points.
- Changing phase in molecular substance involves breaking intermolecular forces, NOT covalent bonds.
- Si and SiO2 have giant structures similar to diamond.
- Si and As are used in semiconductors.
- The p-type semi-conductors are those that are doped with an element with 1 less valence electron (e.g., a group 13 atom added to a group 14 semi-conductor).
- The n-type semi-conductors are those that are doped with an element with 1 more valence electron (e.g., a group 15 atom added to a group 14 semi-conductor).
- Hydrogen fluoride is a weak acid, and it etches glass.
- CFCs (chlorofluorocarbons) are implicated in climate change.
- STP for gases is 273 K and 1.00 atm.
- Kinetic energy of gases depends on their Kelvin temperature.
- Sulfur can exist as S8 molecules.
- Phosphorus can exist as P4 molecules.
- Pure solids, liquids, and gases are never ionized in NIEs, but soluble salts and strong acids and bases IN SOLUTION are.
- When considering valence electrons of p block elements, remember to include the outer s electrons as well (e.g., Al has 3 valence electrons, s2 and p1).
- B and O, and Al and S have slightly lower first ionization energies than we expect, but for different reasons.
- Conjugate acid and base pairs differ in their formula only by H+.
- A very strong acid (e.g., HCl) will have a very weak conjugate base (Cl– ).
- Add concentrated acids and bases to large volumes of water, NOT the other way around.
- Carbon dioxide makes limewater milky.
- The Delta H for the formation of an element is 0 (nothing changes).
- The Delta S for the formation of an element is 0 (nothing changes).
- . . . BUT elements have ABSOLUTE entropies that are NOT 0.
- Catalysts provide alternative pathways for reactions that have lower activation energies.
- Before weighing on electronic balances, allow heated items to cool.
- A beaker/Erlenmeyer flask is NOT a measuring instrument.
- Group 1 oxide + water gives the corresponding hydroxide that is soluble.
- Group 1 metal + water gives the corresponding hydroxide that is soluble AND hydrogen gas.
- Group 1 hydride + water gives the corresponding hydroxide that is soluble AND hydrogen gas.
- Equilibrium systems that undergo changes in pressure should only have their gas molecules considered.
- Lead(II) iodide is a yellow precipitate.
- The TOTAL area under a Maxwell-Boltzmann distribution curve is the same for a reaction at a high and a low temperature.
Count on Carolina's Support
As you soldier on through, remember that Carolina has a full line of AP Chemistry kits, Carolina Investigations® for AP Chemistry, specifically designed for the new AP Chemistry curriculum. The 16 kits in this series address the 6 Big Ideas of chemistry and meet the requirements of the new lab curriculum. Each kit focuses on a single Big Idea and offers the option to do either a guided activity or an inquiry activity with your students. To help students prepare for the AP Chemistry Exam, all kits include Big Idea assessment questions that follow the AP Chemistry Exam's free-response format.
Flexibility to teach AP Chemistry YOUR way
The College Board's new AP Chemistry lab manual contains 16 inquiry labs that teachers can choose from to fulfill the new requirement of 6 inquiry labs in the AP Chemistry course. The materials and quantities needed for these example labs are listed in the document "Materials for AP Chemistry Guided-Inquiry Experiments: Applying the Science Practices". Also included in this document are suggestions for the corresponding Carolina Investigations® for AP Chemistry kits that meet the same Learning Objectives as the College Board example labs.
*AP is a registered trademark of the College Board, which was not involved in the production of, and does not endorse, these products.