LT  =/8 "ALLOY" LAB Materials needed: NaOH solution, about 100 mL Zn, about 25 g (2) 400 mL beakers beaker tong crucible tong clean pennies safety gogles lab apron graduated cylinder balance solid surface hot plate Procedure: 1. Place zinc in beaker. Carefully add sodium hydroxide solution. CAUTION: NaOH is caustic and poisonous! Fill second beaker with clean water and set aside. 2. Heat the sodium hydroxide solution to boiling; add pennies. For best results obseerve the following: a. Make sure the liquid is boiling. b. Stir the pennies and zinc around with the crucible tong to ensure adequate contact between the copper and zinc. c. Leaave the pennies in the liquid for several minutes so that they acquire a good zinc coating (they will look silver-gray). d. The pennies must be clean before use. Soak in vinegar or mild HCl solution and rinse. e. Use no more than about 10 pennies at a time in one beaker. 3. After about 5 minutes (time will vary) carefully remove the pennies. Use the crucible tong to straddle the penny on the edges rather than pinching them from front to back. 4. Rinse the pennies under running water as you remove them from the Zn-NaOH bath and carefully pat them dry. Do not rub the pennies as this will remove the zinc. Pat them dry, making sure they are absolutely dry. Any moisture remaining on the pennies at the start of step 5 will result in dark spots on the finished product. 5. Using the crucible tong, lay the pennies on the hot plate (set on High setting) and leave them there until they change color (5-30 seconds). Remove the pennies from the hot plate, observing the following: a. Do not turn the pennies over. b. Remove the pennies immediately after the color change is observed. c. Dip each penny in cold water as it is removed from the hot plate and dry it. 6. Follow appropriate clean-up procedures.  "@H{wqkqkqk "$BShv 2ysssssssssssssssssssss29oqyyyyyyyyyyyyyyyy2Times New Roman
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