unit 5: energy and light name: unit 5- light and energy · unit 5- light and energy ... what does a...

Unit 5: Energy and Light

Name: _________________________________

Unit 5- Light and Energy Day Description IC/HW Due Date Completed

ALL Warm-up IC

1 Electromagnetic Spectrum Notes IC

1 Light and Energy Notes IC

1 Light and Energy Worksheet HW

1 Flame Test PreLab HW

2 Flame Test Lab HW/IC

2 Light and Energy Calculation

Notes IC

2 Wavelength and Frequency HW

2 Energy HW

2 Gas Tubes Prelab HW

3 Gas Tubes Lab IC/HW

Unit 5 Online Review HW

4 Unit 5 Quiz Review HW

5 Unit 5 Quiz Thursday, November 17th and Friday, November 18th


Warm-up

Day 2

1. What color of visible light has the lowest frequency?

2. What has the shortest wavelength: x-rays or UV light?

3. What has the highest energy: microwave or radiowave?

Day 3

1. What is the frequency of light with a wavelength of 2.38x10-3 µm?

2. What is the wavelength of light with an energy of 420. kJ?

Day 4

1. Draw Bohr’s model of the atom.

2. What is the speed of light?

3. What is Planck’s constant?

Day 5:

1. Calculate the wavelength emitted if the frequency of radiation is 5.09 x1014

Hz? What color would this light be?


Electromagnetic Spectrum Notes

_______________________ is a form of energy that emits wave-like behavior as it travels through space.

Amplitude (a)-

Wavelength (λ)-

Frequency (ν)-

Which of the following has a higher frequency?

Electromagnetic radiation can be displayed in the ______________________.

This spectrum places all of the wave types in order based on wavelength (λ) and frequency (ν).


Light and Energy Notes

In 1900 ____________________ helped us move toward a better understanding of _____________________.

Matter can gain or lose ___________ only in small, specific amounts called __________.

A _____________________ is the __________________ amount of energy that can be gained or lost by an atom.

Light and energy can't always be explained using waves.

In 1905 Albert Einstein proposed that electromagnetic radiation has both ________________and ___________________ like natures.

In the photoelectric effect electrons (or photoelectrons) are emitted from a metal's surface when light or energy of a specific_________________ comes in contact with the metal.

While a beam of light has many _________________ characteristics, the beam can also be thought of as a stream of tiny _________________ or bundles of energy called photons.

A ____________________ is a particle of electromagnetic ______________ with no______________that carries a quantum of energy.

Louis de Broglie (1892 - 1987) o Only ________________numbers of wavelengths are allowed in a circular

orbit of a fixed radius o Light has characteristics of both _______________ and ________________ o Electrons move in ______________ motion with restricted circular orbits

Neils Bohr (1885 - 1962) o Proposed a _____________________ o Predicted frequencies of hydrogen's atomic _______________________ o Atoms have only certain _____________________________ o Related energy states to the motion of electrons in circular orbits


By passing light through an elemental gas: 1. the atoms ____________ energy

2. an electron will move to a __________ energy level.The atom is then said to be in an

_________________state

3) This energy is then released in the form of ___________ when the

electron falls back to the ____________ state.

The ________________ the electron has to fall, the more energy is

released and the _________ the wavelength of light is emitted.

A prism will separate the light into an atomic emission spectrum

Emission Spectrum: series of ___________ which correspond to a

series of ______________ of the _________________ waves

emitted by that element.


Light and Energy Worksheet Answer all questions in complete sentences. 1. Define photon. 2. According to deBroglie, how do electrons move? 3. Draw a picture of Bohr’s atomic model. Label n = 1 – n = 4 and indicate the ground state. 4. What colors are present in white light? 5. List the colors of the visible spectrum in order of increasing energy. The photons of which type of visible light would carry the greatest frequency? 6. What type of visible light has more energy, blue light or orange light? 7. Which type of electromagnetic radiation would be more harmful to humans: microwaves or gamma rays? Explain. 8. Put the following in order from lowest frequency to highest frequency: UV light, Radio waves, infrared and visible light.


9. Which form of electromagnetic radiation would reach Earth faster if both forms were emitted simultaneously from a probe in space: X-rays or gamma rays? Explain. 10. Which photons would have a greater amount of energy: a photons with a wavelength of 125 nm or a wavelength of 3456 pm? 11. Draw a wave and label it with the three characteristic properties of all waves and explain what is meant by each. What units are used to measure λ and ν? 12. Explain the relationship between the frequency and wavelength of a photon. 13. Radio stations can broadcast in an AM frequency or an FM frequency. A popular AM station in Washington is broadcast at 980 kHz (it broadcasts Redskins games) and a popular FM station broadcasts at 97.1 MHz. Which ration station broadcasts with a longer wavelength? 14. Explain what is meant by a quantum of energy. 15. UV – A and UV – B rays will give you a sunburn. If the wavelength emitted by a photon classified as UV-A light is 380 nm and the wavelength emitted by a photon is classified as UV-B is 313 nm, which rays are responsible for the worse sunburn? Explain.


Flame Tests Lab Introduction

According to the Bohr theory of the atom, electrons may occupy only specific energy levels. When an atom absorbs sufficient energy, and electron can “jump” to a higher energy level. Higher energy levels tend to be less stable, however, and if a lower energy level is available, the electron will “fall” back, giving off energy in the process. The difference in energies between the two levels is emitted in the form of a photon of electromagnetic

’s

between 400 and 700 nm, the energy is emitted as visible light. The color of the light depends on the specific energy change that is taking place. White light is a continuous spectrum in which all wavelengths of visible light are present. An excited atom, however, produces one or more specific lines in its spectrum, corresponding to the specific changes in energy levels of its electrons. Because each element has a distinct electron configuration, each has a unique line spectrum. Flame tests are a quick method of producing the characteristic colors of metallic ions. The loosely-held electrons of a metal are easily excited in the flame of a lab burner. The emission of energy in the visible portion of the spectrum as those electrons return to lower energy levels produces a colored flame. The color is a combination of the wavelengths of each transition, and may be used to determine the identity of the ion. In this investigation you will perform flame tests on seven metallic ions, then use your results to determine the identity of several unknowns. Pre-Lab Questions

1. What does a flame test indicate about the energy changes taking place among the electrons in a metallic ion?

2. What wavelengths correspond to the visible spectrum? Which color has the shortest wavelength? The longest?

3. Look up the MSDS for the chemical in the observations section that corresponds with your group number (Group 1 look up LiCl, Group 2 look up NaCl, etc). List the possible hazards of working with this chemical.


Procedure: 1. Light the Bunsen burner. (This process will be demonstrated at the beginning of the lab.) 2. While AT LEAST one member of your lab group stays with the Bunsen burner, take the

crucible tongs to the fume hood and retrieve a q-tip soaked in one of the metals above (make note of which chemical you are doing).

3. Put the q-tip in the Bunsen burner and record the color of the flame in the data table. 4. Place discarded q-tips in a beaker to be disposed of at the end of the lab. 5. WASH THE CRUCIBLE TONGS!!! 6. Repeat for all remaining metals and the two unknowns.

Observations:

1. LiCl

2. NaCl

3. KCl

4. BaCl2

5. CaCl2

6. SrCl2

7. CuCl2

Analysis and Conclusions:

1. Identify the two metals in each of the unknown solutions and explain the reasoning for the identification.

2. Place the known metal ions in order from highest to lowest energy emitted.

3. Compare the energies of the wavelengths emitted for lithium, sodium and potassium. How does the energy emitted relate to the metal’s position on the periodic table? Explain.

4. Is the Bohr model of the atom the most current model? Explain.


Light and Energy Calculation Notes

All electromagnetic waves travel at the same speed in a _______________.

This speed _________ is _______________ in a vacuum. o c is more commonly referred to as the ________________________.

_________________ c = speed of light, 3.00*108 m/s

λ = ______________ ν = ______________

What is the frequency of light with a wavelength of 380. nm?

What is the wavelength of light with a frequency of 98.6 kHz?

________________ E = ____________

h = Planck's Constant, 6.626*10-34 Js ν = ____________

What is the energy of light with a frequency of 1430 MHz?

What is the frequency of light with an energy of 3.40*10-19 J?


Wavelength and Frequency 1. What is the wavelength of a photon with a frequency of 4.5 x 1016 Hz. 2. What is the wavelength associated with a frequency of the radio station 91.9MHz? 3 A laser used in eye surgery to fuse detached retinas produces radiation with a frequency of 4.69 x 1014 Hz. What is the wavelength associated with this frequency? 4. What is the frequency of light with a wavelength of 360nm? 5. What is the frequency of light with a wavelength of 2.32 pm?


Energy 1. What is the energy associated with light that has a frequency of 97.1 kHz? 2. Calculate the frequency of a photon with an energy of 2.3 x 10-22J. 3 A laser used in eye surgery to fuse detached retinas produces radiation with a frequency of 4.69 x 1014 Hz. What is the energy associated with this frequency? 4. What is the energy associated with light with a wavelength of 457nm? 5. What is the energy of a photon with a wavelength of 345 nm? 6. Calculate the wavelength of light with an energy of 4.42*10-19 J. What color is this light?


Unit 5 Quiz Review You must memorize Speed of Light AND Planck’s Constant.

1. For each pair, determine which has the lowest energy, highest frequency, and longest wavelength.

X-ray / Microwave Orange light / Violet light Radiowaves /Gamma Rays

Low Energy: Low Energy: Low Energy:

High ν: High ν: High ν:

Long λ: Long λ: Long λ:

2. Draw a picture of the Bohr model, label the ground state and give the major failing of the model, then explain what happens within an atom when we see light being emitted. 3. List the electromagnetic spectrum in order of decreasing energy. 4. Discuss the contributions of Neils Bohr. 5. Discuss the contributions of Max Planck. 6. Discuss the contributions of Louis deBroglie. 7. Define photon.

8. Indicate which of the following drops would release ultraviolet light and why. n = 2 → n = 1 n = 4 → n = 2 n = 6 → n = 4


Calculations: 9. What is the frequency of light with a wavelength of 5.7*10-7 m? 10. What is the wavelength of a radiowave with a frequency of 87.9 MHz? 11. What is the energy of a photon with a frequency of 53.2 kHz? 12. What is the frequency of a photon with an energy of 6.39*10-15 J? 13. What is the energy of a photon with a wavelength of 7.53 pm? 14. What is the energy of a photon with a wavelength of 345 nm? 15. A laser used in eye surgery to fuse detached retinas produces radiation with a frequency of 4.69 x 1014 Hz. What is the wavelength associated with this frequency? 16. What is the energy associated with the frequency in problem 15? 17. Calculate the energy associated with yellow light with a wavelength of 589nm.

unit 5: energy and light name: unit 5- light and energy · unit 5- light and energy ... what does a...

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