Category Archives: AP Chemistry/SAT Subject

Chemistry SAT class homework, Week of Nov 13, 2017

Please make models of three molecules / ion listed below with paper, sticks and tape:

BF3,  NH3 and (NH4)+

Step 1, write electron configuration of the center atom
Step 2, write Lewis structure of the molecule (i.e. indicate valence electrons with dots around the center atom and terminal atoms)
Step 3, determine polarity of each bond
Step 3, determine the 3-D geometry of electron domain of the molecule
Step 4, determine the geometry of 3-D geometry of the molecule
Step 5, make model of the molecule with paper, sticks and tape
Step 6, indicate the position of each atom on the model (write on)
Step 7, determine if the molecule is polar or non-polar

June 18 Chemistry class

Majority students of this class will take Physics / AP Physics next school year ( survey result at our 06/11 class).  In the class meet on 06/18, I will teach contents of interface of high school Physics and Chemistry, including Wave Properties of Matter, Atomic Spectra, etc.

The division between chemistry and physics melds at their interface where the extrinsic and intrinsic systems of matter combine, notably in such fields as physical chemistry (my  Ph.D. is in physical chemistry), chemical physics, quantum mechanics, nuclear physics/chemistry, materials science, spectroscopy, solid state physics, solid-state chemistry, crystallography, and nanotechnology.

Marie Curie is the only individual to be awarded Nobel Prizes in both chemistry and physics.

June 11 Chemistry classes

I will teach some concepts of Biochemistry / AP Chemistry in June 11 Chemistry classes.

Please bring the book below to the class:

Cracking the AP Chemistry Exam, 2017 Edition (College Test Preparation) by Princeton Review (Author),  ISBN-13:  978-1101919873, ISBN-10:  1101919876.

Please open the link below:

I look forward to seeing you on June 11.

Chemistry SAT Class April 2017 Schedule

  • April 02, Sunday, Newton Chinese School regular class meet.
  • April 09, Sunday, Newton Chinese School regular class meet.
  • April 16, Sunday, Newton Chinese School NO Class (Spring break).  But Chemistry SAT class will meet from 2 PM to 3:30 PM in my house.  This is a make up class for the class missed in January.  (Students who plan to prepare for AP Exam can stay until 5:30 PM if you wish).  Snack will be provided.
  • April 23, Sunday, Newton Chinese School regular class meet (snow day make up).
  • April 30, Sunday, Newton Chinese School regular class meet.

May 1, 2017, Monday, AP Chemistry exam, Morning – 8 a.m. in your high school, 3 hours and 15 minutes.

Jun 03, 2017, Saturday, SAT Chemistry Subject Test, Morning.  Location depends on the choice you made in registration. 60 minutes.

Math skills for SAT and AP Chemistry Exam

Please make sure that you truly master calculation of logarithms in base-10.  Most chemistry textbooks that you use for your chemistry course, has an appendix section at the end of the textbook on logarithms used for chemistry course and SAT Test and AP Exam.

This math skill is important in preparation of Chemistry SAT subject test and AP Chemistry Exam.  The Spring break week is a good time to work on this one.

New AP test (2014 and later)

The 2014 AP Chemistry exam was the first administration of a redesigned test as a result of a redesigning of the AP Chemistry course. The exam format is now different from the past years, with 60 multiple choice questions (now with only four answer choices per question), 3 long free response questions, and 4 short free response questions. The new exam has a focus on longer, more in depth, lab-based questions.

AP Chemistry Test Grade Distribution:

In 2014 (the first test year of the new test design), only 10% of all students who took AP exam scored 5, and 16.6% scored (the worst in five years since 2007)

In 2013 (the last test year before the new test design), 19% of all students who took AP exam scored 5, and 21.5% scored 4

AP Chemistry exam date: Monday, May 04 2015, 8:00 AM

All AP exam dates in 2015:

AP Chemistry Test and Practice

AP Chemistry Test – May 05, 2014 (Monday Morning)

CollegeBoard on-line AP Chemistry exam sample practice:

CollegeBoard on-line AP Chemistry exam sample

Homework for the week of Feb. 03 to 08, 2014

For all students:

On Barron’s AP book, page 445 -447, Practice Excises, #5, ,#6, #9, #10, #18, #19, #20, and #21.

For the students whose high school chemistry class has not covered the Thermodynamics chapter, you must study the following before you try to do this assignment:

  • Eqn (12.31) and the example on Barron’s AP book, page 437, and Appendix 3 on page 750,
  • Eqn (12.32) on Barron’s AP book, page 438,
  • Eqn (12.33) and the example on Barron’s AP book, page 439,
  • Example 12.4 and Example 12.5 on Barron’s AP book, page 440 and 441.

 For the students who plan to take AP exam:

On Barron’s AP book, page 448 -449, Free-Response (a), (b) and (c)*.

* Hint for Free-Response (c):

Measuring Entropy

One useful way of measuring entropy is by the following equation:

ΔS = q/T    (1)

Where S represents entropy, DS represents the change in entropy, q represents heat transfer, and T is the temperature. Using this equation it is possible to measure entropy changes using a calorimeter. The units of entropy are J/K.

The temperature in this equation must be measured on the absolute, or Kelvin temperature scale. On this scale, zero is the theoretically lowest possible temperature that any substance can reach. At absolute 0 (0 K), all atomic motion ceases and the disorder in a substance is zero.  
The absolute entropy of any substance can be calculated using equation (1) in the following way. Imagine cooling the substance to absolute zero and forming a perfect crystal (no holes, all the atoms in their exact place in the crystal lattice). Since there is no disorder in this state, the entropy can be defined as zero. Now start introducing small amounts of heat and measuring the temperature change. Even though equation (1) only works when the temperature is constant, it is approximately correct when the temperature change is small. Then you can use equation (1) to calculate the entropy changes. Continue this process until you reach the temperature for which you want to know the entropy of a substance (25 ºC is a common temperature for reporting the entropy of a substance).The Thermodynamics Table lists the entropies of some substances at 25 ºC. Note that there are values listed for elements, unlike DHfº values for elements. The reason is that the entropies listed are absolute, rather than relative to some arbitrary standard like enthalpy. This is because we know that the substance has zero entropy as a perfect crystal at 0 K; there is no comparable zero for enthalpy. The fact that a perfect crystal of a substance at 0 K has zero entropy is sometimes called the Third Law of Thermodynamics.

The 2014 AP Chemistry exam on Monday, May 5, will be the first administration of a redesigned test

The 2014 AP Chemistry exam will be the first administration of a redesigned test as a result of a redesigning of the AP Chemistry course. The exam format will be different from the past years.

Section I: Multiple Choice;  90 minutes; Number of Questions: 60

Section II:  Free Response; 90 minutes; Number of Questions:  Long Free Response: 3 and Short Free Response: 4

Section II contains two types of free-response questions (short and long), and each student will have a total of 90 minutes to complete all of the questions. This section also contains questions pertaining to experimental design, analysis of authentic lab data and observations to identify patterns or explain phenomena, creating or analyzing atomic and molecular views to explain observations, articulating and then translating between representations, and following a logical/analytical pathway to solve a problem.
Beginning with the May 2014 administration of the AP Chemistry Exam, multiple-choice questions will contain four answer options, rather than five. This change will save students valuable time without altering the rigor of the exam in any way. A student’s total score on the multiple choice section is based on the number of questions answered correctly. Points are not deducted for incorrect answers or unanswered questions.