Developers:

Dr. George W. Pickens, Jr.
F.D.R. Middle School
Bristol Township, PA

Dr. Robert J. Smith
Plastics Additives Research
Rohm & Haas Company

Grade Level:

6 through 8 (Middle School)

Discipline:

Earth Sciences, General Science

Goals:

1. To broaden students' knowledge and understanding of science relationships to everyday living.
2. To make the students aware of science safety rules that should be followed at all times.
3. To work in groups with other students in order to utilize the various scientific behaviors.
4. To help the students develop their problem solving skills.
5. To provide the students with a model of the scientific method.
6. To promote scientific inquiry among the students.
7. To have the students follow written directions.
8. To provide students with information on the effects of ultraviolet radiation.
9. To have the students illustrate the productivity of the spectrum.
10. Upon completion of this laboratory investigation the students will be able to utilize some of their process skills.

Objectives:

1. To be able to work together as a scientific team.
2. To be able to brainstorm and share ideas with other class members.
3. To collect and record data for utilization in science and math.
4. To recognize each team member's ability to contribute to a team effort,
5. To identify problem areas.
6. To understand the meaning of ultraviolet radiation and how it affects the world.
7. To be able to use and define the words included in the glossary.
8. To learn how to research information.
9. To identify the various materials and chemicals in the paper making process.
10. To be able to develop and use a number of the process skills that are listed: observation, comparison, computation, estimation, relating, communication, measurement, reading, inference, designing, applying, recording, diagramming, library use, classifying, predicting, comprehension, hypothesizing, drawing conclusions, vocabulary writing, constructing models.

Safety:

1. Before doing any experiment be sure to refer to your school's laboratory safety guidelines.
2. Read all directions for an experiment before proceeding.
3. Always ask your teacher for assistance if you are not sure what to do.
4. Do not experiment on your own.
5. Always wear safety glasses when working in the laboratory.
6. Only perform the activity assigned to you by your teacher.
7. Do not directly look into the UV lamps (blacklights) if you are using them for this experiment.

Background:

Ultraviolet (UV) radiation is one form of radiation emitted by the sun, and it affects all

forms of life on earth. While UV radiation has been here for as long as the earth itself, we are learning more about its effects every day. We know that there are three types of UV radiation, UVA, UVB, and UVC, and all are harmful to mankind to varying degrees. They may cause premature aging, altering of the immune system, cataracts, skin cancer, and sunburn. Because of these health effects you need to limit your exposure to UV radiation by always utilizing the best protection when outside. The different types of UV radiation are defined by their wavelength. The shorter the wavelength the more energy the radiation contains and the more damaging it may be.

The amount of UV radiation you receive depends on the intensity of the sun and the transmission properties of the atmosphere. These would include: a) the time of day, b) the season, c) the altitude, d) the amount of cloud cover, e) surface reflection effects, f) your latitude, and g) length of exposure.

Time of Day - 75% of the UV radiation is received between the hours of 10 a.m. and 3 p.m., when the sun is at its highest point in the sky. If you are outside and your shadow is shorter than you are you should take extra precautions to protect against UV exposure. This is true all year around.

Seasons - more UV radiation is received during the summer (May - August in the northern hemisphere) than in winter. There is less seasonal difference as one nears the equator, and one must take this into consideration regardless of the season.

Altitude - more UV radiation reaches the earth at high altitudes where the air is cleaner and thinner. As a general rule there is about 9% increased UV radiation for every mile increase in altitude.

Clouds - while clouds will block out much visible light and infrared light (heat) by casting shadows on the earth, they still permit much of the UV radiation to penetrate. Thus, you can still get sunburns on cloudy days, even though the sun feels much less intense.

Surface reflection - reflection from ground surfaces is normally low, but reflection from fresh snow can be as high as 80%. This increases the amount of UV radiation you receive. Another reflecting surface is water.

Where you live - as mentioned above, altitude, surface conditions, and seasonal variations all can increase the amount of UV radiation exposure. Thus, where you live may increase one or more of these effects.

Length of exposure - the longer you are exposed to the sun the more UV radiation you receive. Always consider your daily activities, such as walking in the neighborhood, to the train station, or the bus, getting the mail, or walking the dog, when evaluating your exposure to UV radiation.

The result of overexposure to UV radiation can be sunburn. The pigmentation of the skin will determine the speed at which the skin will burn. Fair-skinned people need only 15-30 minutes to burn, while people with moderately pigmented skin may require 1-2 hours. While those with darkly pigmented skin will not normally sunburn, they must still take precautions against other damaging effects of UV radiation.

Skin cancer is the most common form of human cancers, and is divided into two basic groups, non-melanoma and melanoma types. Melanoma is the fastest growing form of cancer in the United States with over 32,000 new cases and almost 7,000 deaths each year. Non-melanoma cancers are rarely fatal, but should not be taken lightly.

Photo-aging is displayed by deep wrinkles, dryness, accentuated skin furrows, mottled pigmentation, and loss of elasticity of the skin. The use of UV sunscreens inhibits photo-aging. Cataracts are also formed by overexposure to UV radiation, causing clouding of the eye, and can greatly reduce vision.

The UV Index was formed to make you aware and informed about UV radiation and the amount of time you spend in the sun. A National UV Index was made available by the Environmental Protection Agency (EPA), the National Weather Service, and the Center for Disease Control. Daily advisories are given each day to make you aware of the strength of the sun's UV radiation in your area. The higher the UV Index level, the greater the strength of the sun's UV rays and the faster you will burn. The index is not based on surface observations, but is a computerized forecast based on forecast ozone levels (ozone adsorption reduces UV levels), forecast cloud cover, and the elevation for the area included in the index. There are two satellites being operated by the National Oceanic and Atmospheric Administration that are responsible for the measurements of the current total ozone amounts for the entire globe. The information collected is the time of day (solar noon) day of the year, and its latitude.

Classroom Management:

Students may work in groups of 5 with the following responsibilities.

one student will be the leader

one student will be the recorder

one student will be the equipment getter

two students will be the experimenters

Student write-up requirements:

All students are to complete their own individual experiment write-ups.

Each write-up should include group number along with any additional information or corrections that need to be made.

The teacher should see the completed results for the investigation before the experimental write-up is handed in. The write-up should include all the necessary information . Each group should be sure to have the recorder include all names on his or her paper in order to receive full credit.

Scientific Method Steps:

1. Define and state the problem.
2. Gather information on the problem.
3. Form or state a hypothesis.
4. Experimenting by testing the hypothesis.
5. Observing.
6. Recording and analyzing the data.
7. State all the conclusions and results.

Materials:

File folders (manila) with the face cover cut into a number of flaps (the number will vary with the experiment).

Newsprint (blank or printed pages with large amounts of open space)

UV fluorescent light (black light)
UV filter material
Graph paper
Pencil
Scotch™ tape
Scissors
Metric ruler
Weights

The following are suggestions relevant to all the activities.

Planning the observations and thinking about results:

1. Have the students start a science journal that they will use during the school year.
2. Before actually doing the experiment record what you think you will find out.
3. Decide what type of observations will be needed for you to do in order to complete the experiment successfully.
4. Let each group compare their results with those of other groups.

Things to consider when drawing conclusions:

1. How many time intervals did you have?
2. Did the different time intervals help to influence the final outcome?
3. Were your final results affected by the weather?
4. Would cloud cover affect your results? If so, how? If not, why not?
5. What part did UV radiation play in your experiment?
6. When do you think the greatest amount of UV radiation would be given off?
7. List some of the conditions that were impossible for you to control.
8. Did you have any type of problem or difficulty in completing your experiment?
9. What did you learn from doing this experiment?

Extensions:

1. Allow students to have longer periods of time to complete their experiments.
2. Compare and contrast this experiment by using different seasons.
3. Have students try various different types of filters.
4. Provide ideas for the students to do experiments like this at home.
5. Design another experiment using the information presented on UV radiation.
6. Let students compare their results with other classes.
7. Have students use various types of light sources: incandescent and/or fluorescent light bulbs.
8. Predict and observe how long it takes for the newsprint (end roll) to change color.
9. Invite a research scientist to your classroom to give you an overview of what his job consists of.

Activity 1: What type of light causes newsprint to yellow?

Hypothesis: ???

Procedure:

1. Cut a piece of newsprint approximately 20 cm x 30 cm from a roll end or from the newspaper.
2. Cut a 20 cm x 10 cm piece of UV filter material.
3. Cut a manila folder cover into three flaps (see Fig. 1). Each flap will be about 10 cm wide.
4. Tape the newsprint to the inside (uncut portion) of the manila folder.
5. Tape the filter to the newsprint directly under one of the flaps made in Step 3.
6. Place the folder with the newsprint outside in direct sunlight or inside under a fluorescent blacklight. Open the flap over the portion with the UV filter material and one of the other flaps. Leave one flap covering the newsprint. (Note: you may need to weigh the folder and flaps down with heavy weights, especially if you are doing this experiment outside).
7. Periodically observe the newsprint for signs of yellowing. Depending upon the time of year or other conditions this may take from several hours to a day or more. When the portion of the newsprint not under the filter is visibly yellowed return the folder to the classroom and observe the results.
8. Compare the color of the newsprint under each flap. Did the newsprint covered with the UV filter material respond differently than that exposed directly to the sun or the UV lamp? Did it respond differently from the newsprint that was completely covered during the experiment?
9. Record your results and conclusions. Do they support the hypothesis?

Extension Activities:

1. Do the same experiment as above but include other materials as filters, such as window glass, colored glass, clear plastics.
2. Compare the results with those in the above experiment. Do these other transparent materials affect the paper in the same way as the UV filter? Do you think you could do the experiment using the sun as the light source inside (on a windowsill, for example)?

Activity 2: How does the time of day affect the amount of UV radiation the earth receives?

Procedure:

NOTE: Depending upon the time available to do this experiment you may want to change the observation times suggested below.

1. Cut a piece of newsprint approximately 20-cm x 30-cm from a roll end or from the newspaper.
2. Cut a manila folder cover into five equal sized flaps (see Fig. 1).
3. Tape the newsprint to the inside (uncut portion) of the manila folder.
4. Label each of the flaps with the time of day that portion of the paper is to be exposed. For example, if you want to measure the exposure every two hours you might have flaps labeled: 0800-1000; 1000-1200; 1200-1400; 1400-1600; plus one flap as a control (to remain closed, no exposure).
5. Label the folder with your name, date, location of exposure, weather conditions, temperature. If conditions change, you can note this as well.
6. Place the folder outside in direct sunlight at (in this example) eight o'clock in the morning (0800) with the 0800-1000 flap open exposing that portion of the paper to the sun. Be sure to weigh down the flaps so they stay open or closed as desired.
7. At each appropriate interval (1000, 1200, 1400, in this case) close the previous flap and open the next.
8. At the end of the designated period (1600 in this example) close the last flap and return the folder to the classroom for examination.
9. Observe each exposed area for the amount of yellowing. Record your observations. Are the areas exposed during different times of the day different? Can you estimate the difference between the different areas, if any? (Note: if the paper did not yellow enough in one day to make good observations, repeat the experiment with the same piece of paper on additional days until you can see a distinct yellow color develop).

Activity 3: How does the time of year affect the amount of UV radiation the earth receives?

Procedure:

Note: this experiment obviously requires an extended period of time. For a normal school year we suggest you try to expose one each month. Given the probability of bad weather during the year we suggest you try this experiment indoors.

1. Prepare a folder with as many flaps as you need for the time available (eight or nine, perhaps, for a typical school year) plus one for a control (no exposure).
2. Insert a piece of newsprint into the folder and mark the edge of each flap with a pencil line.
3. Open the first flap and expose that portion of paper for long enough to develop a significant amount of color (perhaps one or two days), but be careful to note the exact hours used to expose the paper.
4. Return the folder to the classroom and store it closed and in a dark place.
5. One month later repeat the exposure in the same location for exactly the same period of time. Try to do this experiment on clear days if possible.
6. Continue this experiment for as many months as possible. Note: be sure to watch out for Daylight Savings Time!
7. At the end of your experiment compare the exposures. Record you observations and conclusions. Be sure to include the control in your observations.

Activity 4: How does the weather affect the amount of UV radiation the earth receives?

Procedure:

Note: to control for any effects you may discover in Activity 3 this experiment should be conducted on days as close together as possible. Planning ahead with the weather forecast to assure different weather conditions may help.

1. Prepare a folder with as many flaps as you need for the time available (six, for example, if you intend to check the results each day for a week).
2. Insert a sheet of newsprint in the folder as described in earlier experiments.
3. Expose one portion of newsprint each day, taking care to record the weather during the period.
4. Compare and record the results from each day. Report the results and conclusions.

Extension Activities:

1. The class could contact students in other parts of the country (or the world even, using the Internet) and coordinate an experiment to compare the effects of various different factors on UV exposure such as weather, latitude, elevation, rural or urban environment, etc. To control the study the class would probably want to supply their partners in the experiment with paper from a single source, although adding newsprint from different areas might be an interesting additional experiment.

This experiment is courtesy of