Hands-on science (no lab required).After reading "Who Dunnit?" (p. 8), try this hands-on experiment to learn how scientists lift fingerprints Impressions or reproductions of the distinctive pattern of lines and grooves on the skin of human fingertips. Fingerprints are reproduced by pressing a person's fingertips into ink and then onto a piece of paper. and match them with a person. PREDICT: When you touch different surfaces, you often leave fingerprints, or a "stamp" showing your fingertip's 'tiny bumps bumps a term used to describe a variety of papulonodular dermatoses in horses, including 'heat bumps', 'feed bumps', 'protein bumps', 'wheat bumps' and others. No specific disease or etiology has been assigned to the term and veterinary dermatologists wish it would disappear from use. and grooves Grooves is an American electronic music magazine founded in 1999 by editor Sean Portnoy, initially concentrating on the then-burgeoning IDM music genre and expanding to its more experimental, abstract offshoots, such as microsound, microhouse and glitch, eventually . Police use special techniques to lift these prints. Which fingerprint-lifting technique do you think will work better: dusting the print with baby powder, dusting it with salt, or not dusting the print? YOU NEED: three paper towels * baby oil (10 drops) * one magazine * baby powder (5 ml, or 1 tsp) * trash can In the Macintosh, a simulated garbage can used for deleting files and folders. The trash can keeps the files intact in case the user wants to restore them, but can be "emptied" from time to time to save disk space. * clear plastic tape * one sheet of black construction paper * magnifying glass magnifying glass: see microscope. magnifying glass traditional detective equipment; from its use by Sherlock Holmes. [Br. Lit.: Payton, 473] See : Sleuthing * paper and pencil * salt (5 ml, or 1 tsp) PROCEDURE 1. Form groups of two or more students. 2. Fold a paper towel in half. Put three drops of baby oil onto it. 3. Rub your pointer pointer, breed of large sporting dog developed in England more than 300 years ago. It stands between 23 and 26 in. (58.4–66.4 cm) high at the shoulder and weighs between 50 and 60 lb (22.7–27.2 kg). finger over the oil spot on the paper towel. Then, to make sure the fingertip fin·ger·tip n. The extreme end or tip of a finger. isn't too oily, press it once onto a dry spot on the paper towel. 4. Press the "oiled" fingertip onto a page of a magazine. Have another student note the spot where you pressed your finger. 5. Sprinkle the fingerprint fingerprint, an impression of the underside of the end of a finger or thumb, used for identification because the arrangement of ridges in any fingerprint is thought to be unique and permanent with each person (no two persons having the same prints have ever been with 5 ml (1 tsp) of baby powder, or enough to cover the fingerprint. 6. Remove excess powder by shaking the magazine over a trash can. Then, blow across the powdered area to remove more of the powder. 7. Have another student place a 2.5 cm (1 in.) piece of clear plastic tape over the fingerprint. Gently press down on the tape with one finger. NOTE: Do NOT rub your finger over the tape. 8. Slowly peel the tape off the magazine, and stick it onto a sheet of black construction paper. NOTE: Do NOT rub the tape when sticking it onto the paper. 9. Use a magnifying glass to observe the fingerprint. Record your observations. For example, are the fingerprint lines visible? 10. Repeat Steps 2 to 9, this time using salt instead of baby powder. 11. Repeat Steps 2 to 9, this time skipping Steps 5 and 6. This trial does not require dusting the fingerprint, so it is your "control." CONCLUSIONS: 1. Which of the three fingerprinting fingerprinting Act of taking an impression of a person's fingerprint. Because each person's fingerprints are unique, fingerprinting is used as a method of identification, especially in police investigations. methods--dusting with baby powder, dusting with salt, or not dusting--lifted the best print? Explain. 2. To get a high-quality fingerprint, would you use a fine or coarse powder? Why? TAKE IT FURTHER: Have each student make a fingerprint using the method that worked best. Compare your prints. For guidance, check out the FBI's fingerprinting Web site: www.fbi.gov /kids/k5th/what wedo3.htm ANSWERS 1. The baby powder should have given the best fingerprint. That's because its individual particles are lightweight and fine-grained, so they easily stick to the fingerprint's tiny ridges. The salt crystals are too coarse and heavy to reveal the fingerprint's delicate features. And without using a powder, the prints are too difficult to see. 2. A fine powder would give the highest-quality fingerprint. The individual particles of the fine powder are light enough to stick to the oily fingerprint. Also, the particles are fine enough to trace out the tiny ridges of the fingerprint. |
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