Chapter 4

The Bohr Model of the AtomPart 2

Quantum Leaps

• A quantum leap is a change of an electron from one energy state to another within an atom.

• Quantum leaps cause the absorption and emission of electromagnetic radiation in which “excited” atoms release small packets of electromagnetic energy called photons.

Some Uses of “Exciting” Atoms (Quantum Leaps)

•Spectroscopy is the study of the energy which is given off and absorbed when atoms go from the ground state to the excited state and back again.•Spectroscopy is often used in chemistry for the identification of substances, through the spectrum absorbed or emitted.

Spectroscope

Dust in black hole winds helped form early stars E-mail | Save | Print |

Astronomers have taken a baby step in trying to answer the cosmic question of where we come from. Planets and much on them, including humans, come from dust — mostly from dying stars. But where did the dust that helped form those early stars come from?

A NASA telescope may have spotted one of the answers. It's in the wind bursting out of super-massive black holes.

The Spitzer Space Telescope identified large quantities of freshly made space dust in a quasar about 8 billion light years from here.

Astronomers used the telescope to break down the wavelengths of light in the quasar to figure out what was in the space dust. They found signs of glass, sand, crystal, marble, rubies and sapphires, said Ciska Markwick-Kemper of the University of Manchester in England. She is the lead author of a study that will be published later this month in Astrophysical Journal Letters.

Dust is important in the cooling process to make stars, which are predominantly gas. The leftover dust tends to clump together to make planets, comets and asteroids, said astronomer Sarah Gallagher, a study co-author at the University of California Los Angeles.

"In the end, everything comes from space dust," Markwick-Kemper said. "It's putting all the pieces of the puzzle together to figure out where we came from."

Astronomers figure that the planets that formed in the past several billion years — and those away from quasars — came from dust that was belched from dying stars. That's what happened with Earth.

That still leaves a question about where the dust from the first couple billion years of the universe came from, which helped form early generations of star systems.

"It's formed in the wind," of the black holes, Markwick-Kemper said. Gas molecules collide in the searing heat of the quasar, which is thousands of degrees Fahrenheit, and form clusters.

"These clusters grow bigger and bigger until you can call them dust grains," she said.

Scientists who weren't part of the study hailed the work.

Cornell University astronomer Dan Weedman, the former director of NASA's astrophysics division, said the study was an important step in answering a fundamental mystery of the early universe.

The entire article is posted near the door of the classroom if you would like to read more.

Fireworks

Light Sources – Mercury

CFL’sThe average rated life of a CFL is

between 8 and 15 times that of incandescents. CFLs typically have

a rated lifespan of between 6,000 and 15,000 hours, whereas

incandescent lamps are usually manufactured to have a lifespan of

750 hours or 1,000 hours.

Mercury Vapor Lamp

• Spectrum of a CFL bulb. The camera had a diffraction grating in front of the lens. The discrete images are produced by the different colors in the light, a line spectrum. An incandescent lamp would instead have a continuous band of color.

Neon Signs

Lasers

• You'll find them in everything from CD players to dental drills to high-speed metal cutting machines to measuring systems. Tattoo removal, hair replacement, eye surgery -- they all use lasers.

What else can lasers be used for?

Sharks

I want sharks with laser beams attached to their heads.

Flame Tests

Flame Tests• A flame test is a procedure used in chemistry to

detect the presence of certain metal ions based on each element's characteristic emission spectrum.

Video: Molecular FingerprintsStudent Worksheet

Use Windows Media Player

Homework

Summarize the purpose and procedure for the “Flame Test” Lab.

Continue to work on Chapter 4 Worksheet 3.

Study Guide Chapter 4 (2 pages) is due tomorrow.