BELLWORK 10/30/18

# BELLWORK 10/30/18

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## BELLWORK 10/30/18

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1. BELLWORK 10/30/18 • Is light a wave or a particle?

2. OBJECTIVES • Students will be able to explain how light behaves as a light and a wave • Students will be able to explain how the emission of light is related to the behavior of electrons. • Students will summarize how the absorption and emission of light led to the development of the Quantum Mechanical Model of the Atom.

3. Chapter 4 – Arrangement of Electrons in Atoms • Rutherford’s model of the atom explained the location of the atom’s sub-atomic particles. • However; it did not explain why the negatively-charged electrons orbiting the nucleus were not pulled inside of the positively-charged nucleus. • In the early 20th century, investigations into the properties of light led to the discovery of the relationship between light and an atom’s electrons.

4. The Development of a New Model of the Atom • A new model of the atom began when scientists began investigating the properties of light. • Before the 1900, scientist believed that light behaved solely as a wave. • It was later discovered that light also exhibited particle –like behavior. • Before we discuss the dual wave-particle nature of light, we first need to define waves and particles.

5. WHAT IS A WAVE? • WHAT ARE THE 4 CHARACTERISTICS OF A WAVE?

6. ANSWER • A wave can be described as a disturbance that travels through a medium, transporting energy from one location (its source) to another location without transporting matter. What happens to the wavelength as the frequency increases?

7. Relationship between wavelength and frequency Wavelength Frequency The number of waves that pass a given point in one second. • The distance between corresponding points on adjacent waves. C = wavelength (λ) x frequency (v) c = (λ) (v) C= constant for the speed of light = 3.00 x 108 m/s When wavelength increases, frequency decreases and vice versa

8. What is a Particle?

9. ANSWER • A particle is a small piece of anything. Particle can also refer to a subatomic particle with mass and structure, but takes up hardly any space at all. Particles are tiny. ... These particles are even smaller than atoms. You can also say a crumb or speck of something is a particle.

10. The Dual-Wave Particle of Light • Before 1900, scientists thought light behaved solely as a wave, but this concept was proven incorrect. • It is now known that light has characteristics of both waves and particles.

11. VIDEO- IS LIGHT A PARTICLE OR A WAVE?

12. So, after watching the video, what is light?

13. PHOTOELECTRIC EFFECT • When electromagnetic radiation strikes the surface of the metal, electrons are ejected from the metal, causing an electric current. • Light has to be traveling at a minimum frequency in order to release electrons.

14. Real life applications of the Photoelectric effect • A solar panel works by allowing photons, or particles of light, to knock electrons free from atoms, generating a flow of electricity. Solar panels are comprised of many smaller units called  photovoltaic cells, that convert sunlight into energy

15. Dual Wave-Particle Nature of Light Evidence of light traveling as waves Evidence of light traveling as particles Light is absorbed and emitted by matter, such as the photoelectric effect Light can be emitted by hot objects, and the line-emission spectra of elements. • Light contains frequency and wavelengths that can be measured. • Light can interfere and diffract.

16. The Wave Description of Light • Visible light is a kind of electromagnetic radiation, which is a form of energy that travels as waves through space. • All of the forms of electromagnetic radiation form the electromagnetic spectrum. • The electromagnetic spectrum contains gamma rays, x-rays, ultraviolet light, visible light, infrared, microwaves, and radio waves. • The electromagnetic spectrum covers a wide range of wavelengths and frequencies.

17. VIDEO- PARTICLES AND WAVES

18. BELLWORK – 10/31/18 • WHAT IS AN EMISSION SPECTRUM? • WHAT CAUSES AN ELECTRON TO JUMP TO A HIGHER ENERGY LEVEL? • WHEN HYDROGEN GAS IS PLACED INTO A DISCHARGE TUBE AND PROVIDED AN ELECTRICAL CURRENT, WHAT SPECTRAL LINES ARE OBSERVED? • WHAT CHARACTERISTIC GLOW CAN BE SEEN?

19. ANSWER • AN EMISSION SPECTRUM SHOWS THE COLORS OF LIGHT GIVEN OFF WHEN THE ATOMS OF AN ELEMENT ABSORBS ENERGY. • BEING HIT BY A PHOTON THAT CONTAINS THE MINIMUM FREQUENCY. • VIOLET, BLUE-VIOLET, BLUE-GREEN, AND RED • PINK

20. Activity (Cont) • Complete #’s 7-17 with your partner. • 10 minutes

21. Review #’s 7-17

22. COMPLETE #’S 18-23 • 15 MIN

23. BELLWORK - 11/01/18 USING WHAT YOU HAVE LEARNED ABOUT EMISSION SPECTRA, WHAT INFORMATION CAN YOU DERIVE FROM THE DIFFERENT COLORS OF THESE STARS? Betelgeus: (Beetle Juice) Vega Vega was the first star other than the Sun to be photographed and the first to have its spectrum recorded. This bright red supergiant is roughly 650 light-year from Earth. Also known as Alpha Orionis,

24. ANSWERS– 11/01/18 • Stars emit colors of many different wavelengths, but the wavelength of light where a star's emission is concentrated is related to the star's temperature - the hotter the star, the more blue it is; the cooler the star, the more red it is. • Basically, the color of light that a star emits is somewhat related to its age. • Throughout most of a star's life, it is burning hydrogen at its core, which creates lots of energy and thus makes it appear blue. ... Thus, younger stars can appear bluer while older ones appear more red, and in this way, a star's color can tell us something about that star's age

25. REVIEW #’S 18-23

26. VIDEO

27. HOW IS VISIBLE LIGHT PRODUCED? • An atom’s electron (absorbs / releases) energy and becomes energized, or_______. When this happens, the electron moves from its ______ _______ (lowest energy level) to an ______ _______ (higher energy level) • As the electron returns to its ground state, it (emits / absorbs) the color of light that it originally absorbed.

28. ANSWERS • An atom’s electron (absorbs / releases) energy and becomes energized, or_excited. When this happens, the electron moves from its _ground state (lowest energy level) to an excitedstate(higher energy level) • As the electron returns to its ground state, it (emits / absorbs) the color of light that it originally absorbed.

29. HOW CAN FLAME TESTS HELP US TO IDENTIFY DIFFERENT ELEMENTS? • RESEARCH THE PURPOSE OF FLAME TESTS, AND WHY AND HOW THEY ARE USED.

30. FLAME TEST PRE-LAB

31. CHECKPOINT • QUIZIZZ