Monthly Archives: October 2014

Chemistry SAT homework for the week 10/27/2014

Cracking the SAT Chemistry Subject Test, 2013-2014 Edition (College Test Preparation), Princeton Review, ISBN: 978-0-307-94556-3 (0-307-94556-1):

Chapter 6   Atomic Structure and the Periodical Table of the elements he Building Blocks of Matter

Solve Question Type A:  9, 10 and 11, on Page 73.

  1. Solve Question Type B:  105 and 106 on Page 73.

Solve Question Type C:  31, 32 and 33 on Page 74.


Cracking the AP Chemistry Exam, 2014 Edition (Revised) (College Test Preparation), Princeton Review, ISBN-13: 978-0804124751 ISBN-10: 0804124752:

Chapter 3 Questions, Page 40 – 41

Multiple-Choice Questions: #7, #9, #14, #15


Facebook CEO Mark Zuckerberg Dazzles With Mandarin —— His Chinese language skills stunned the audience    Zuckerberg’s Chinese interview — in Mandarin video  (start at 0.30 second)


Dear parents,


The essay submitted to 牛顿中文学校第三届星光杯作文大赛 will be counted as 小作文: (题目自命) (20) in the midterm exam on November 02,即:参赛学生不要求为期中考试再交一篇作文。

For the details, please open the link below:

 ———- Forwarded message ———-
From: NCLS Comm <>
Date: Mon, Oct 20, 2014 at 5:33 PM
Subject: Hi from the Writing Contest Committee
Dear Lead Teachers,

We hope this note finds you well.  As the deadline of the writing contest approaches, we are hoping you can help contact your colleagues in the same grade on our behalf.

Please ask the teachers to remind the parents of the deadline of the coming contest.  The announcement is posted on school main page and also available at the below location –

Your helping with encouraging the participation is much appreciated.

Thank you,

The Writing Contest Preparation Team

How Blue LEDs Work, and Why They Deserve the Physics Nobel Prize

Background information: Red and green light-emitting diodes (LED) have been with us for almost half a century, but not blue LED

By Don Lincoln on Thu, 09 Oct 2014

In the early hours of October 7, 2014, … The Nobel Committee often recognizes grand discoveries, like the prediction of the Higgs boson and the observation of the accelerating expansion of the universe. Thus many were surprised to see the 2014 prize honor a very practical invention: blue light emitting diodes.  

The technical achievement

LEDs are one of many useful spinoffs from the basic science of quantum mechanics. In the standard quantum cartoon, electrons orbit the center of atoms, kind of like planets around the Sun. (The planetary model is not completely accurate, but it has many good features that help visualize what is going on in the quantum realm.) Imagine a simple atom with a single electron. According to quantum mechanics, the electron can be in a series of discrete orbits, as if a single planet around our Sun could be in the orbit of Mercury or Venus or any of the planets, but nowhere in between. Electrons near the nucleus have lower energy, while ones farther away have more energy.

When an electron moves from a high-energy orbit to a lower-energy one, it emits energy in the form of light. The color of the emitted light depends on the energy difference between the old orbit and the new one. The bigger the energy difference, the bluer the light.

The greatest benefit on mankind

To understand why this seemingly mundane development warrants such recognition, one must return to Alfred Nobel’s will, in which he provided the seed money to start the prizes that bear his name. When Nobel’s brother died, a French newspaper mistakenly published Alfred’s obituary. Alfred Nobel was horrified to see himself called a “merchant of death” and a man “who became rich by finding ways to kill more people faster than ever before.” He resolved to repair his legacy by bequeathing a prize to be awarded to “those who…have conferred the greatest benefit on mankind.” Nobel wanted to be remembered as a man who helped make the world a better place.

This year’s award clearly fits the bill. “I really think that Alfred Nobel would be very happy about this prize,” said Per Delsing, head of the Nobel Committee for Physics, in announcing the prize. ”It’s really an invention and it’s really something that will benefit most people.”

The invention of bright blue LEDs brought entirely new industries into existence. Now, blue, red and green LEDs could be combined to make white—or any other color—light. This development led to the power-efficient screens for cell phones, TVs, computers, iPads, and many other electronic miracles of the modern world.

However the real impact of blue LEDs goes well beyond our rainbow-colored gadgets. Today, LEDs are bright enough to use as light sources. Just as Thomas Edison’s original incandescent light bulb revolutionized the early years of the 20th century, LEDs are poised to revolutionize the 21st.

LEDs can now emit far more light using far less power than incandescent and fluorescent bulbs. For instance, an incandescent light bulb can emit about 16 lumens per watt of electrical power, and a fluorescent light manages about 70 lumens per watt. In comparison, a modern white LED can emit 300 lumens per watt, meaning that it consumes only about 5% of the power of an incandescent. Given that about a quarter of the world’s electricity is used to generate light, the invention of efficient lighting can have considerable economic and environmental impact, potentially reducing the greenhouse gas emissions that are driving anthropogenic global warming. In the developing world, bright, efficient LEDs could provide solar-powered, off-grid energy for homes, hospitals, and more.

This year’s Nobel Prize in physics is very well deserved and reflects Alfred Nobel’s desired legacy of recognizing discoveries and developments that have greatly benefited mankind.

Structure of Atom: in class practice excises, October 19, 2014

hint:  go to Princeton Review AP Chemistry book, page 275 to find the equation and the constant

  1. What are the frequency of and energy of blue light that has wavelength, λ, of 400.0 nm?
  2. What are the wavelength, λ, and the energy of light that has a frequency of 1.50 X 1015 S-1?
  3. Determine the energy and wavelength of light associated with an electron moving from the second (n = 2) to the fourth (n = 4) energy level in a hydrogen atom.

Chemistry SAT homework for the week 10/12

On Cracking the SAT Chemistry Subject Test, 2013-2014 Edition (College Test Preparation), Princeton Review, ISBN: 978-0-307-94556-3 (0-307-94556-1):

Chapter 4   Atoms: The Building Blocks of Matter

  1. Solve Question Type B:  105 and 106, on Page 47.
  2. Solve Question Type C:  27 on Page 47.

Homework to be completed prior to 10/05/2014 Chemistry SAT class

1.      Wave–particle duality:

A theory that proposes that every elementary particle including electron exhibits the properties of not only particles, but also waves.


 2.      Single particle

The momentum of a particle is traditionally represented by the letter p. It is the product of two quantities, the mass (represented by the letter m) and velocity (v):

P = mv

Go to Princeton AP book, page 275, find above equation and the definition of p and m and v.

3.     Heisenberg’s uncertainty principle:

It tells us that it is impossible to simultaneously measure the position and momentum of a particle with infinite precision, i.e. (Δp((Δx) ≥ h/4π  

Heisenberg established this expression as the minimum amount of unavoidable momentum disturbance caused by any position measurement.  He refined his principle:

\Delta x \, \Delta p\gtrsim h\qquad\qquad\qquad (1)

Go to Princeton AP book, page 275, find the definition and value of of h (Planck’s constant) in the above equation.

This equation reveals that the more accurately a particle’s position is known, or the smaller Δx is, the less accurately the momentum of the particle Δp is known. Mathematically, this occurs because the smaller Δx becomes, the larger Δp must become in order to satisfy the inequality. However, the more accurately momentum is known the less accurately position is known. 

(In our everyday lives we virtually never come up against this limit).

You may see

 \Delta x\, \Delta p \ge \frac{\hbar}{2}

\hbar = {{h}\over{2\pi}} = 1.054\ 571\ 726(47)\times 10^{-34}\ \text{J⋅s} = 6.582\ 119\ 28(15)\times 10^{-16}\ \text{eV⋅s}.