Lab Work Chemical Changes

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Observation of Chemical Changes

Purpose
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.

Procedure
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

2.Hydrochloric Acid + Bromothymol blue
3.Ammonia + 1 drop Bromothymol blue
4.Hydrochloric acid + blue dye
5.Blue dye + Sodium Hypochlorite. Observe & add 1 drop of hydrochloric acid. 6.Potassium iodide + Lead Nitrate. A precipitate should form. 7.Sodium hydroxide + phenolphthalein.
a.Phenolphthalein is an acid-base indicator.
8.Hydrochloric acid + phenolphthalein.
a.What color would be expected when combining phenolphthalein with an acid or with a base? 9.Sodium bicarbonate + Silver nitrate
10.Silver nitrate + Ammonia
a.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

Observations

Data Table 1: Reactions Expected
Question # / Well #
Chemicals
Reaction
1- A1NaHCO3 and HCI - C02 Bubbling. Color unchanged.

2- B1
HCI and BTB Golden yellow color change.
3- C12NH3 and BTBBubbling. Blue color change.
4- D1HCI and blue dyeCloudy. Green color change.
5- E1Blue dye and NaOCIInitially blue, then yellow and bubbling. 6- F1KI and Pb(NO3)2Yellow color change. Fizzing then opaque precipitate. 7- H1NaOH and phenolphthaleinCloudy.
8- G1HCI and phenolphthaleinClear....
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