Lecture 4

Question 1

Atomic number

Answer 1

Number of photons in nucleus

Question 2

Atomic mass number

Answer 2

protons +neutrons

Question 3

Isotope

Answer 3

Same number of protons but different number of neutrons

Question 4

Familiar phases

Answer 4

solid, liquid, gas and not so familiar phase: plasma

Question 5

Ionization

Answer 5

stripping of electrons, changing atoms into plasma

Question 6

Dissociation

Answer 6

breaking of molecules into atoms

Question 7

Evaporation

Answer 7

breaking of flexible chemical bonds, changing liquid into gas

Question 8

Melting

Answer 8

breaking of rigid chemical bonds, changing solid into liquid

Question 9

Phases and Pressure

Answer 9

Phase of a substance depends on both temperature and pressure
Often more than one phase in present

Question 10

How is energy stored in atoms?

Answer 10

• The energies of electrons in atoms correspond to particular energy levels
• Atoms gain and lose energy only in amounts corresponding to particular changes in energy levels

Question 11

What are the three basic types of spectra?

Answer 11

Emission line spectrum
Continuous Spectrum
Absorption line spectrum

Question 12

Continous Spectrum

Answer 12

The spectrum of a common (incandescent) light build spans all visible wavelengths, without interruption

Question 13

Emission Line Spectrum

Answer 13

A thin or low density cloud of gas emits light only at specific wavelengths that depend on its composition and temperature, producing a spectrum with bright emission lines

Question 14

Absorption Line Spectrum

Answer 14

A cloud of gas between us and a light bulb can absorb light of specific wavelengths leaving dark absorption lines in the spectrum

Question 15

Energy levels of Molecules

Answer 15

Molecules have additional energy levels because they can vibrate and rotate

Question 16

Thermal Radiation

Answer 16

Nearly all large or dense objects emit thermal radiation, including stars, planets, you.
An objects thermal radiation spectrum depends on only one property: its temperature

Question 17

Properties of Thermal Radiation

Answer 17

1. Hotter objects emit more light per area at all frequencies
2. Hotter objects emit photons with a higher average energy : higher temperature - higher peak and more towards blue