U2 - Module 1: Analyzing Light-Matter Interactions

Question 1

What are the two types of light graphs?

Answer 1

1. Absorption
2. Emission

Question 2

What is another term for light?

Answer 2

Electromagnetic (EM) Radiation

Question 3

What is the process of light being absorbed?

Answer 3

• Light is shined on an object
• An object absorbs some of the light
• The light that reaches the other side of the object is dimmer.

Question 4

What is the process of light being emitted?

Answer 4

• An object/element is heated up
• Light is emitted off of the object

Question 5

Electromagnetic (EM) Radiation

Answer 5

Energy traveling through space as waves formed by oscillating electric and magnetic fields.

Question 6

Wavelength

Answer 6

The distance between each wave

Question 7

Frequency

Answer 7

How often a wave occurs
- # of waves per __

Question 8

What is the symbol for wavelength?

Answer 8

λ (lambda)

Question 9

What is the symbol for frequency?

Answer 9

v

Question 10

What is the relationship between wavelength and frequency?

Answer 10

Inverse
- As wavelength increases, frequency decreases
(vice versa)

Question 11

What is the formula for speed of light?

Answer 11

wavelength x frequency

Question 12

What is the range of visible light?

Answer 12

400-700 nm

Question 13

Ultraviolet light

Answer 13

Light that is lower than 400 nm

Question 14

Infrared Light

Answer 14

Light that is greater than 700 nm

Question 15

Why do atoms and molecules interact with EM Radiation?

Answer 15

They are made up of charged particles (electrons and protons)

Question 16

What happens to energy when atoms/molecules interact with light?

Answer 16

Energy is absorbed or released

Question 17

Spectroscopy

Answer 17

The analytical techniques based on the analysis of EM radiation absorbed/emitted by a chemical substance

Question 18

Absorption Spectroscopy

Answer 18

EM Radiation is passed through an object and we measure the radiation that is absorbed

Question 19

What does it mean when a wavelength region is not absorbed?

Answer 19

It is reflected

Question 20

What happens to the color of an object when it absorbs all colors except 1?

Answer 20

The color of the object is the color of light that it reflected

Question 21

What happens to the color of an object when it absorbs only 1 color but reflects the rest?

Answer 21

The color of the object is the opposite of the color absorbed on the color wheel.

Question 22

What type of electromagnetic radiation has the shortest rays?

Answer 22

Gamma radiation

Question 23

Does it take more or less energy to ionize an atom in the n=3 state, compared to ground state?

Answer 23

Less energy
- Atom is farther from the nucleus
- There are less attractive forces the further from the nucleus

Question 24

What electromagnetic radiation has the longest wavelength?

Answer 24

Radio waves

Question 25

What electromagnetic radiation has the shortest wavelength

Answer 25

Ultraviolet photon

Question 26

What are the two graphs that represent absorbance of light?

Answer 26

1. Absorbance 2. Transmittance

Question 27

What is the relationship between transmittance and absorbance?

Answer 27

The greater the level of transmittance, the lower amount of light being absorbed.

Question 28

How does the transmittance graph work?

Answer 28

-The peaks of the graph go downwards - The greater the dip, the larger amount of transmittance occurring

Question 29

What does the light emission graph display?

Answer 29

The specific colors of light that are emitted when the material is heated up.

Question 30

What does the number of wavelengths of light emitted mean?

Answer 30

The complexity of the molecule - More wavelengths means a more complex molecule

Question 31

What is unique about each atom?

Answer 31

Has its own set of emission spectra

Question 32

What do the different colors of light emitted represent?

Answer 32

The different specific wavelengths the atom emits.

Question 33

Quantization

Answer 33

Electrons exist in specific energy states

Question 34

Explain the steps of quantization.

Answer 34

1. The energy levels are quantized; electrons can only exist in the specific energy level, not between 2. When a photon of light is absorbed that has an energy level of an exact difference between two energy levels, the electron jumps to a higher energy state. 3. The electron remains in the higher energy state until it becomes unstable, and will eventually return to a lower state. 4. As the electron moves back down to a lower energy level, it emits a photon with an energy equal to the distance of the energy level.

Question 35

Emission

Answer 35

As the electron loses energy, it emits a photon of light that is equal to the amount of energy lost.

Question 36

What level of photon light absorbed causes an electron to move to a higher energy state?

Answer 36

A photon with an energy level equal to the distance of the energy levels.

Question 37

What causes electrons to move to higher energy levels?

Answer 37

Certain wavelengths absorbed (colors)

Question 38

What color is not included in the quantization of wavelengths?

Answer 38

Yellow light

Question 39

Why is a photon emitted after electrons move down energy levels?

Answer 39

There is excess energy in the atom due to moving down energy levels, and the excess is emitted through the photon.

Question 40

What is the formula for finding energy transferred?

Answer 40

E = h (planck's constant) x v (frequency)

Question 41

What is the relationship between frequency and energy levels?

Answer 41

Directly proportional - As energy increases, so does frequency

Question 42

What is the relationship between wavelength and energy levels?

Answer 42

Inversely proportional - As the wavelength increases, the energy decreases.

Question 43

What unit is energy in?

Answer 43

Joules (J)

Question 44

What value does "C" stand for?

Answer 44

The speed of light.

Question 45

What value does "h" stand for?

Answer 45

Planck's constant

Question 46

How many kilojoules in 1 Joule?

Answer 46

1000 kJ

Question 47

What do transitions with larger energy differences result in?

Answer 47

Shorter wavelengths (higher energy photons)

Question 48

Where can isolated atoms exist?

Answer 48

Different electronic energy states

Question 49

What are the isolated atoms location dependent on?

Answer 49

How their electrons are distributed among different energy levels.

Question 50

What changes the electrons energy state that they are in?

Answer 50

The absorption/emission of energy

Question 51

What are the 3 different molecule excitation states?

Answer 51

1. Electronic state 2. Vibrational energy state 3. Rotational energy state

Question 52

Electronic Energy

Answer 52

Energy is associated with electrons in a molecule

Question 53

Rank the order of energy required based off the 3 molecular energies changes.

Answer 53

1. Electronic (highest) 2. Vibrational 3. Rotational (lowest)

Question 54

What causes the transition in the electronic energy state?

Answer 54

Absorption/emission of photons

Question 55

What light region is electronic energy found in?

Answer 55

- UV - Visible

Question 56

Rotational energy state

Answer 56

Energy is based off of the rotation of a molecule around its center of mass

Question 57

What causes the transition in the rotational energy state?

Answer 57

Absorption/emission of low energy photons

Question 58

What light region is rotational energy found in?

Answer 58

Microwaves

Question 59

Vibrational energy state

Answer 59

Associated with the vibrations of atoms within a molecule (bonds stretch, break and twist)

Question 60

What causes the transition in the vibrational energy state?

Answer 60

The absorption of IR radiation causes an increase in vibrational levels

Question 61

What light region is vibrational energy found in?

Answer 61

Infrared

Question 62

How do you convert from J of energy to kJ of energy?

Answer 62

Multiply the J of energy by avogadros # Then divide by 1000

Question 63

How do you convert from energy of a single photon to energy of a mole of photons?

Answer 63

Multiply the energy value by avogadros number

Question 64

What must happen for a wavelength to move to a higher energy level?

Answer 64

Needs to give the SPECIFIC amount of energy to go from one level to another.

Question 65

What is a mole considered?

Answer 65

A counting term

Question 66

What happens when an electron loses energy?

Answer 66

The energy lost goes to making a photon of light equal to the same amount of energy lost.

Question 67

Ground state

Answer 67

No excited electrons