Hands-on science (no lab required).After reading "Sugar Load" (p .14), try out this hands-on hands-on adj. Involving active participation; applied, as opposed to theoretical: "We're involved in hands-on operations, pulling levers, pushing buttons" Arthur R. Taylor. experiment to learn how different chocolates melt. PREDICT Which type of chocolate has a lower melting point melting point, temperature at which a substance changes its state from solid to liquid. Under standard atmospheric pressure different pure crystalline solids will each melt at a different specific temperature; thus melting point is a characteristic of a substance and : a candy-coated or non-coated chocolate? Does the size of a piece of chocolate affect its melting time? YOU NEED 5 plastic bags (sealable, quart-size) ** chocolate (1 M&M, 2 whole Hershey's Kisses Hershey's Kisses are a type of chocolate candy manufactured by The Hershey Company. The bite-sized pieces of chocolate have a distinctive shape: people normally describe them as flat-bottomed teardrops. , 2 Hershey's Kisses cut in half) ** thermometer thermometer, instrument for measuring temperature. Galileo and Sanctorius devised thermometers consisting essentially of a bulb with a tubular projection, the open end of which was immersed in a liquid. * 5 plastic cups (8 oz, or 250 ml) ** *2 milk jugs (4 L, or 1 gal)-one filled with 27[degrees]C (80[degrees]F) tap water, and the other with 40[degrees]C (105[degrees]F) tap water ** watch or timer timer, n radiographic timing device that functions as an automatic exposure timer and a switch to control the current to the high-tension transformer and filament transformer. The face of the timer is calibrated in seconds and fractions of seconds. ** tablespoon ta·ble·spoon n. Abbr. T, tbsp. A measure of about 3 teaspoons or 15 milliliters. tablespoon a household unit of volume or capacity; equivalent to three teaspoons or approximately 15 milliliters; in metric ** paper (graph and plain) ** pencil * See teacher's note, TE 7 ANSWERS * Teacher's Note: The two jugs of water should be sufficient for a whole average-size class. 1. The M&M should have resulted in the highest melting point. That's because the water's heat has to travel through the M&M's coating before it reaches the chocolate inside. 2. Yes, the whole chocolate kiss Noun 1. chocolate kiss - a kiss that consists of a conical bite-sized piece of chocolate chocolate candy - candy made with chocolate candy kiss, kiss - any of several bite-sized candies takes longer to melt than the half-size Adj. 1. half-size - half the usual or regular size little, small - limited or below average in number or quantity or magnitude or extent; "a little dining room"; "a little house"; "a small car"; "a little (or small) group" piece. That's because the chocolates melt when enough heat moves from the water to the chocolate. It takes longer to transfer enough heat to raise the temperature of a larger solid compared with a smaller one. 3. The chocolate kisses should melt in your hand, because chocolate's melting point is lower than the average human body temperature: 37[degrees]C (98.6[degrees]F), PROCEDURE 1. Divide into groups of 3 to 4 students. 2. Put 1 M&M, 1 Hershey's Kiss, and 1 half-piece Hershey's Kiss into separate plastic bags, and seal. 3. Pour a half-cup (125 ml) of 27[degrees]C (80[degrees]F) water into each of three cups. 4. Measure the cups' water temperatures using a thermometer. Record these temperatures. 5. Place each bag into a cup. Make sure the water level covers the chocolate candies. 6. Time one minute on a watch, and then remove the bags from each cup. 7. Observe each bag for a chocolate smear smear (smer) a specimen for microscopic study prepared by spreading the material across the slide. Pap smear , Papanicolaou smear see under test. . This signals melting. (Gently press on the M&M to check for melting.) 8. Record observations. 9. If you don't see a smear, add 2 tablespoons of hot water (40[degrees]C, or 105[degrees]F) to that candy's cup. 10. Repeat Steps 4 to 9 until each piece of chocolate shows signs of melting. The temperature at which each candy candy: see confectionery. candy Sweet sugar- or chocolate-based confection. The Egyptians made candy from honey (combined with figs, dates, nuts, and spices), sugar being unknown. melts is its melting point. 11. Place 1 whole and 1 half-piece chocolate Kiss into separate bags, and seal. 12. Get two fresh cups. Combining water from the hot and cool water jugs, fill each cup with a half-cup (125 ml) of water until its temperature reaches the melting point found for the whole chocolate Kiss. 13. Repeat Steps 4 and 5. 14. Time how long it takes for the whole and half chocolate Kisses to melt completely. Record the times. 15. Make two bar graphs: one showing the melting points for all three chocolates, another showing the melting times for the whole and half chocolate Kisses. CONCLUSIONS 1. Using your graphs, which chocolate piece had the highest melting point? Explain. 2. Did the chocolate's size affect its melting time? Why or why not? 3. Which chocolate piece will melt in your hands? Hint: Think about the average human body temperature. WEB EXTRA Learn more about candy science at: www.exploratorium. edu/cooking/ candy/index.html. [ILLUSTRATION OMITTED] |
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