Chemistry Homework #9

Pg 360 #1-8

1.     Write an equation or a sentence that describes the relationship between the frequency of electromagnetic radiation and its energy.

a.     The relationship between the frequency of electromagnetic radiation and its energy is proportional; if the frequency has a high rate of oscillation (high-frequency radiation) then the amount of energy is high as well.

2.     Why is the word spectrum a good descriptor of the types of energy found in electromagnetic radiation?

a.     The word spectrum is good because it describes a large variety of energy, from low energy to high energy.

3.     Why is visible light useful in plant photosynthesis, while other forms of electromagnetic radiation are not?

a.     Visible light is useful because it reacts with the molecules of chlorophyll, which provides energy in order to produced photosynthesis reactions.

4.     A. List the main types of electromagnetic radiation in order of increasing energy.

a.     UV-A Radiation

b.     UV-B Radiation

c.      UV-C Radiation

B. Describe how each type of radiation listed in your answer to Question 4a affects living things.

       a.    UV-A Radiation has the lowest energy; no effect

       b.    UV-B Radiation has more energy; linked to sunburn and skin cancer.

       c.    UV-C Radiation has the most energy and can break covalent bonds;

             used to sterilize because it can kill bacteria and destroy viruses.

5.     Ultraviolet light is often used to sterilize chemistry laboratory protective goggles. Why is ultraviolet light effective for this use, while visible light is not effective?

a.      It’s frequency radiation, or oscillation levels, are so high that it can kill bacteria.

6.     Compare infrared, visible, and ultraviolet radiation in terms of how well they are absorbed by the atmosphere.

a.     INFRARED: it is well absorbed by the atmosphere; most of the radiation from the sun cannot reach the Earth’s surface because CO2 and gaseous H2O molecules in the atmosphere absorb it.

b.     VISIBLE: not well absorbed; on a clear day, more than 90% of the visible region of solar radiation directed toward Earth travels down to Earth’s surface.

c.      ULTRAVIOLET: well absorbed; most of the UV-B radiation, and much of the UV-A radiation, does not reach Earth’s surface. It is absorbed by the stratospheric ozone layer.

7.     Describe two main effects of the solar radiation that reaches the Earth’s surface.

a.     Maintaining a habitable average temperature on Earth:

                                               i.     The greenhouse gases help to moderate the amount of solar radiation that reaches the Earth’s surface by use of carbon dioxide and water vapor, which readily absorb infrared radiation, for example.

b.     Determining the climates and weather:

                                               i.     Earth’s rotation, yearly revolution, and tilt on its axis. This causes an uneven distribution of solar radiation, which cause the four distinct seasons.

8.     A. Compare lake water and asphalt in terms of how readily each warms up when exposed to sunlight.

a.     The lake water would absorb the infrared radiation and heat up faster because it is similar to clouds, in that clouds are made of droplets of water, but the radiation also powers the hydrologic cycle.

b.     Asphalt would heat up slower because it reradiates the incoming radiation, which helps balance Earth’s energy.

B. What properties of these two materials account for differences in their behavior?

a.     Lake water: absorption of infrared radiation

                  b.  Asphalt: reradiation of incoming radiation.