Department of Chemistry
Observations of Chemical Changes
Lab Section: Chem-181DL1
The purpose of the experiment Observation of Chemical Changes is to examine the properties of chemical reaction and relate those reactions to products commonly found in a home environment. Through this experiment someone can macroscopically analyze whether a solution is acidic or base and identify the presence of starches in food. Procedure
For each of the combinations of chemicals below put 2 drops of each in their own well in the 96-well plate. Making sure to place only 2 drops of the first chemical then adding only 2 drops of the second chemical the observation of the reaction can be made. To properly observe the titrations move them between a dark background and a white background. a. NaHCO3 & HCI- bubbles form
b. HCI & BTB
c. NH3 (Ammonia) & 1 drop of BTB- record expected color & actual result. d. HCI & blue dye
e. Blue dye & NaOCI. Record findings, then add 1 drop of HCI f. NaOCI & KI. Observe, then add 1 drop of starch. See starch turns black g.KI & Pb(NO3)2. Describe precipitate formed.
h.NaOH & phenolphthalein. Observations of Chemical Changes i. HCI & phenolphthalein. With phenolphthalein & acid what color do you expect?-clear. What color do you expect with a base?-fuchsia
j. NaOH and AgNO3 .
k. AgNO3 and NH3 (ammonia). Absorb mixture onto paper towel, expose to intense light from a light bulb or the sun. Be patient and observe change. l. NH3 and CuSO4
Almost every solution made had some type of chemical reactivity. Most solutions changed colors revealing the acidity or alkalinity of a chemical and some exposing the presence of starch. The exception in the change of appearance was the chemicals HCI and phenolphthalein which was in the...
References: 1. Labpaq-General College Chemistry-50-0123-ck-01 Lab Manual- Published by Hands-On Labs Inc. 3880 S. Windermere St. Englewood, CO 80110
2. Chemistry & Chemical Reactivity, the 8th edition by Kotz, TreIchel, Townsend, Publisher Thomson, Brooks/cools 2012, Belmont, CA 94002-3098. ISBN-13: 978-0-8400-4828-8
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