Observation of Chemical Changes
In this experiment, the student studied the composition of materials in a setting where the indications of chemical changes were safely observed. The changes observed consisted of bubble formation, colors, viscosity, and precipitate formation.
Using a well plate: use a different well for each chemical combination. Two drops (unless otherwise noted) of each chemical in the combinations (below) should be placed in one well. A dark and light piece of paper should be available to slip under the well as the student observes the changes that are occurring. As each reaction occurs, record the well number and observations. 1.
Sodium Bicarbonate + Hydrochloric Acid
Hydrochloric Acid + Bromothymol blue
Ammonia + 1 drop Bromothymol blue
Hydrochloric acid + blue dye
Blue dye + Sodium Hypochlorite. Observe & add 1 drop of hydrochloric acid. 6.
Potassium iodide + Lead Nitrate. A precipitate should form. 7.
Sodium hydroxide + phenolphthalein.
Phenolphthalein is an acid-base indicator.
Hydrochloric acid + phenolphthalein.
What color would be expected when combining phenolphthalein with an acid or with a base? 9.
Sodium bicarbonate + Silver nitrate
Silver nitrate + Ammonia
Using a paper towel, absorb the mixture onto a paper towel and hold in front of a strong light bulb. Observe the changes that will slowly occur. 11.
Ammonia + Copper (II) sulfate
Data Table 1: Reactions Expected
Question # / Well #
NaHCO3 and HCI - C02
Bubbling. Color unchanged.
HCI and BTB
Golden yellow color change.
NH3 and BTB
Bubbling. Blue color change.
HCI and blue dye
Cloudy. Green color change.
Blue dye and NaOCI
Initially blue, then yellow and bubbling. 6- F1
KI and Pb(NO3)2
Yellow color change. Fizzing then opaque precipitate. 7- H1
NaOH and phenolphthalein
HCI and phenolphthalein
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