Chapter 3 Review Worksheet

1. Chapter 3 Review Worksheet

2. Describe the plasma phase of matter. Under what conditions is matter a plasma?

3. A plasma is a hot gas made of charged atoms, called ions. Atoms become charged when they are stripped of electrons in a process called ionization. This happens at very high temperatures.

4. Describe the difference between transparent and opaque materials.

5. A transparent object allows light to pass through it or transmits light. The plastic bag is transparent to infrared light. • An opaque object absorbs light. The plastic bag is opaque to visible light.

6. Why do objects appear to have a certain color? • Interactions between light and matter determine the appearance of everything around us. • Objects appear a certain color based on the colors of light they reflect!

7. Describe the major regions of the electromagnetic spectrum in terms of wavelength, frequency and energy.

8. How is the wavelength related to the frequency?

9. Describe the characteristics of continuous, emission, and absorption spectra and the conditions under which each is produced.

10. Continuous Spectrum • An unbroken band of colors produced by glowing solids, liquids & high pressure gases. • Ex: The spectrum of a common (incandescent) light bulb spans all visible wavelengths, without interruption

11. Emission Line Spectrum • Produced by hot gases under low pressure. • EX: 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

12. Absorption Line Spectrum • Produced when a continuous spectrum of light is passed through a cooler, low pressure gas. • EX: A cloud of gas between us and a light bulb can absorb light of specific wavelengths, leaving dark absorption lines in the spectrum

13. Briefly describe the structure of an atom. • Nucleus- contains protons & neutrons • Electron cloud- contains electrons • electrons are arranged in energy levels in the cloud

14. What is electrical charge? Will an electron and a proton attract or repel each other? • Electric charge is a property of protons (+) and electrons (-). They attract each other. This is what holds an atom together.

15. The most common form of iron has 26 protons and 30 neutrons. State its atomic number, atomic mass number, and number of electrons if it is electrically neutral. • Atomic number = 26 • Mass number = 56 • Electrons = 26

16. Consider the following three atoms: atom 1 has 7 protons and 8 neutrons; atom 2 has 8 protons and 7 neutrons; atom 3 has 8 protons and 8 neutrons. Which two are isotopes of the same element? • Isotopes have the same number of protons. Atoms 2 and 3 are isotopes.

17. Explain how electron transitions within atoms produce unique emission and absorption spectra.

18. Explain how electron transitions within atoms produce unique emission and absorption spectra. • Electrons gain energy (by absorbing light) and jump to a higher level • Electrons lose energy ( by emitting light) and drop to a lower level • The only allowed energy changes are those corresponding to a transition between levels Not Allowed Allowed

19. Explain how electron transitions within atoms produce unique emission and absorption spectra. • Each transition corresponds to a unique photon energy, frequency, and wavelength Energy levels of Hydrogen

20. Explain how electron transitions within atoms produce unique emission and absorption spectra. • Downward transitions produce a unique pattern of emission lines

21. Explain how electron transitions within atoms produce unique emission and absorption spectra. • upward transitions produce a pattern of absorption lines at the same wavelengths

22. Explain how electron transitions within atoms produce unique emission and absorption spectra. • Each type of atom has a unique spectral fingerprint • Observing the fingerprints in a spectrum tells us which kinds of atoms are present

23. The following labeled transitions represent an electron moving between energy levels in hydrogen. a. Which transition, as shown, is not possible? Transition 3 isn’t possible because it only goes halfway from level 2 to level 3

24. b. what is the wavelength of light associated with transition 5? Is the photon being absorbed or emitted?

25. How can we use emission or absorption lines to determine the chemical composition of a distant object? We compare the spectrum of the object to known spectra. Each element has a unique internal structure. Therefore, when an electron moves from one energy level to another in an atom of a given element it involves a photon of light at a wavelength that’s unique for that element. If this spectral line is observed then, we know it must have been produced by that element.

26. Describe two ways in which the thermal radiation spectrum of an 8,000 K star would differ from that of a 4,000 K star. • The peak wavelength for the hotter star will be shorter (shifted more to the UV end of the spectrum. The curve will also be taller showing that it emits more light at all wavelengths than the cooler star.

27. Suppose the surface temperature of the Sun were about 12,000 K, rather than 6,000 K. • How much more thermal radiation would the sun emit?

28. b) What would happen to the Sun’s peak wavelength? • If the sun’s temperature doubled it’s peak wavelength would decrease. The current peak is at about 450 nm which is in the visible portion of the spectrum. The new peak would be in the uv portion of the spectrum .

29. Describe the Doppler Effect for light and what we can learn from it. • The Doppler effect is the change in wavelength of light caused by motion between the source and the observer. • If the source is moving toward the observer the light is blueshifted • If the source is moving away from the observer the light is redshifted