Lab Practical Midterm

Lab Practical Midterm - This handout is to be reused....

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1 O # Chem 151 Lab Practical Midterm Sunscreens: Chemical Protection against the Sun Mad dogs and Englishmen Go out in the midday sun. The Japanese don’t care to, The Chinese wouldn’t dare to, Hindoos and Argentines sleep firmly from twelve to one. But Englishmen detest a - Siesta. - Noel Coward, English Author and Playwright from the song “Mad Dogs and Englishmen”, 1930 The dangers of long-term exposure to intense sunlight have long been known to mankind. Tropical cultures have developed many coping mechanisms including lots of loose clothing and staying out of the sun during the most intense part of the day. More recently medical research has shown a connection between extensive intensive exposure to the sun and increased risk of skin cancer, among other ailments. Modern western culture has chosen to discard the more traditional methods of protection from the sun’s harmful rays and substitute concoctions known as sunscreens . In this experiment you will investigate how sunscreens are constructed to provide protection from ultraviolet radiation. Educational Objectives: A student who has successfully completed this experiment will be able to # perform a simple extraction, # measure the absorbance of solutions in the UV range, # evaluate the differences in absorbances between samples, and # write a suitable report. Experimental Objectives: A student who performs this experiment is asked to # extract the UV absorbing components of a commercial sunscreen, # measure the absorbance of the extract, # normalize the results from different samples # determine the relationship between absorbance and SPF rating, and # write a report. This handout is to be reused. Please do not mark on it. Return it when you submit your report.
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O PRACTICAL MIDTERM # 2 Background Ultraviolet radiation is considered dangerous because it is capable of breaking chemical bonds at normal temperatures. This makes it a concern when it comes into contact with our bodies, particularly our skin. Long term exposure to UV radiation can lead to cataracts and other eye disorders, skin damage including cancer, premature aging, and immune system damage. Due to these dangers the Environmental Protection Agency (EPA) has created a UV Index to help citizens determine how to manage UV exposure (see table 1). The best way to protect oneself from
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This note was uploaded on 06/12/2008 for the course CHEM 151 taught by Professor Staff during the Spring '08 term at Arizona.

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Lab Practical Midterm - This handout is to be reused....

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