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Observations of Chemical Changes

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Ocean County College
Department of Chemistry
Observations of Chemical Changes

Date Submitted: 09/22/2013
Date Performed: 09/19/2013
Lab Section: Chem-181DL1
Course Instructor: Dr. Nancy Marashi

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Observations of Chemical Changes
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The purpose of this experiment is to observe and examine some of the properties of chemicals reactions and relate these chemical properties with household products. In this experiment, different chemicals are examined to observe how they react and interact with one another.

Chemical List

Materials From:
Label or Box/Bag:QtyItem Description
Student Provided 1

Sheet of white paper, sheet of dark paper
Paper towel
Distilled water
Small amounts of household cleaning

From LabPaq

Auxiliary Supplies
Auxiliary Supplies
1Pipet, Empty Short Stem

Experiment Bag
Observations of
Chemical Changes

1Aqueous Ammonia, 1 M – 1 mL
Bromthymol Blue, 0.04% – 2 mL in Pipet
Copper (II) Sulfate, 0.2 M – 2 mL in Pipet
FDC Blue Dye #-1, 0.1% – 2 mL in Pipet
Hydrochloric Acid, 1.0M-1 mL
Lead (II) Nitrate, 0.2 M – 2 mL in Pipet
Potassium Iodide, 0.1 M – 2 mL in Pipet
Silver Nitrate, 0.1 N – 2 mL in White
Dropper Bottle
Sodium Bicarbonate, 1 M – 2 mL in Pipet
Sodium Hydroxide, 1 M – 1 mL

Sodium Hypochlorite, 1% – 2 mL in Pipet
Starch Solution, 1% Stabilized – 2 mL Pipet

For each combination of chemicals, a 96-well plate was used for each set of chemicals. First, for all combinations, 2 pipet drops were added to one well and then 2 drops followed the second chemical, unless it stated underwise in the instructions. The mixtures were observed against white and dark paper as background under the well plate. For each reaction, the well number of the mixtures and observations were recorded. The combination of chemicals were:

a) NaHCO3 (sodium bicarbonate-baking soda) and HCl (hydrochloric acid)
b.) HCl and BTB (Bromothymol blue)
c.) NH3 (ammomnia, a base) and 1 drop of BTB
d.) HCl and blue dye
e.) Blue Dye and NaOCl (sodium hypochlorite). The reaction was observed and then 1 drop of HCl was added
f.) KI (potassium iodide) and Pb(NO3)2 (lead nitrate)
g.) NaOH and phenolphthalein
h.) HCl and phenolphthalein
i.) NaOH and AgNO3 (silver nitrate)
j.) AgNO3 and NH3. This mixture was absorbed into a piece of paper towel and exposed to a light bulb.
k.) NH3 and CuSO4 (Copper (II) sulfate)
For each mixture, reactions such as color, precipitation, and cloudiness were observed and recorded. After successful completion, the leftover chemicals were disposed by absorbing the left chemicals with paper towels. The well plates were washed with distilled water and dried with paper towels. The left over pipets were washed several times to discard any
chemicals left. Lastly, hands were washed.

Data and Observations

Data Table 1: Reactions Expected
Well #/ Question
A1NaHCO3and HCI – C02Clear, bubbles formed= CO2

HCI and BTBOrange color, homogeneous
A3NH3and BTB
Dark blue (much lighter dark blue under white paper/ darker, opaque dark blue under dark paper)

A4HCI and blue dyeGreen color, homogenous
A5Blue dye and NaOCIBlue color, then 1 drop HCL added = blue-greenish color, more focused on green, homogenous A6KI and Pb(NO3)2Yellowish, cloudy precipitate
A7NaOH and phenolphthaleinDark pink color, homogenous
A8HCI and phenolphthaleinNo bubbles, clear, homogenous
A9NaOH and AgNO3Light brownish, cloudy precipitate
A10AgNO3and NH3Clear, some small bubbles at the bottom
A11NH3and CuSO4Light blue, cloudy precipitate

As the above table shows, the reactions of different combination of chemicals were observed and recorded. The reactions were analyzed under white and black paper for backgrounds. Well A1 showed a clear color with bubbles forming carbon dioxide. Well A2 showed an orange color and well A3 formed a dark blue color. After previous mixtures, it seems that when BTB (Bromothymol blue) is mixed with an acid, it turns into an orange color and when mixed with a base it forms a dark blue color. Well A4 formed a green color, where the white paper showed a lighter green and the black paper appeared with a darker green. The mixture in well A5 showed a blue color.
Then 1 drop of HCl added turned the mixture into a blue-greenish color, with a greater emphasis on green.

Wells A6 showed a yellowish, cloudy precipitate and A7 formed a dark pink color. The color observed in well A8 was a clear homogeneous mixture. It appears that when phenolphthalein is mixed with an acid, the mixture remains clear and when mixed with a base, it forms pink. Wells A9 mixture formed a light, brownish precipitate and A10 remained clear. Nevertheless, when mixture A10 was absorbed into a piece of paper towel, the clear color changed to a light brown spot after exposure to a light bulb for an hour. The last mixture A11 formed a light blue precipitate. Questions:

A. Suppose a household product label says it contains sodium hydrogen carbonate (sodium bicarbonate). How would you test this material for the presence of sodium bicarbonate?
I would test it with different chemicals in separate well-plates to see if there is a reaction the same way Table 1 shows. A well may have HCl mixed with sodium bicarbonate and record whether the mixture forms any clear bubbles, any sign of strong odor. It could also be tested with phenolphthalein to see if a change occurs, forming a dark pink color or staying clear.

B. You know what color phenolphthalein and bromothymol blue turn when testing an acid or a base. Use the empty pipet in the Auxiliary Supplies Bag to test several (at least 3) household items including household cleaning products with bromothymol blue. Rinse the pipet well before using it on the next household chemical. When finished with this experiment rinse the pipet well and return it to the Auxiliary Bag for use in future experiments. Name the items tested and record their results. What do these results mean?

3 household items tested: Windex (original), Lysol, and 409 All-purpose Cleaner. Lysol mixed with BTB formed bubbles with an opaque green color. Windex mixed with BTB showed a dark blue color. Lastly, 409 All-purpose Cleaner mixed with BTB showed formed bubbles and a blue color. These
results mean that Windex and 409 All-purpose Cleaner are bases and Lysol is an acid.

C. You found a sample of a solution that has a faint odor resembling vinegar. You are verifying that it is indeed vinegar and you add a few drops of phenolphthalein. The sample turns pink. What assumption can you make about this sample?

Vinegar is an acid. Phenolphthalein only forms a pink color when it is mixed with a a base. This means that the sample of solution is not vinegar.

D. You decided to investigate if the new wave of Vitamin Water is pH neutral: neither too acidic nor too basic. Using BTB (bromothymol blue), you select five flavors of Vitamin Water to test. Three of the flavor-samples turn a murky green, indicating the likelihood of acid/base balance. Of the two remaining, one turns slightly yellow, while one remains blue. What can you assume about the acid/base content of these particular flavors of Vitamin Water?

When Bromthymol Blue is mixed with an acid it will turn orange-yellowish and when mixed with a base will form a blue color. I can assume that the Vitamin Water that remained blue is more towards a base than an acid. The Vitamin Water that turned yellow is more towards an acid than a base.

E. You have read that a new brand of hair tonic is supposed to contain lead (an ingredient in Grecian Formula). Devise a simple test to confirm the presence or absence of lead in that hair tonic.

Lead nitrate mixed with potassium iodide will form a yellowish color, a cloudy mixture. I would mix a small quantity of hair tonic with potassium iodide to see its reaction. If it turns into a yellowish color or maybe forms a precipitate or both, I would assume that lead is present in the hair tonic. If another color appears or remains clear, then, I would assume that there is no lead in the tonic.

Throughout this experiment, chemical changes were observed, where the color of each mixture was analyzed. The main objectives were careful seen in the properties of each mixture. In the lab manual it mentions how we cannot see the individual atoms and molecules reacting but we are able to observe color changes, precipitates and formation of bubbles. This experiment was successful in identifying bubbles formation and expected reactions when BTB reacts with an acid or a base and when phenolphthalein reacts with an acid or base, among other reactions. Based on previous combinations, it can be concluded that certain chemicals work better with acids and others with bases. This experiment showed possible reactions that we can use for further studies in determining which mixtures are stronger as a base or as an acid. This experiment was also able to associate chemical properties with some of the most important household products used in everyday life. By analyzing chemical reactions, you can assume and determine the acid or base content of the chemical. This set of chemical tests satisfied the principle of finding the properties and main reactions between chemical combinations in order to have a better understanding on how these chemicals react with one another.

1. General College Chemistry. LabPaq. Hands-On Labs, Inc. pgs.14-20.

Cite this Observations of Chemical Changes

Observations of Chemical Changes. (2016, Nov 19). Retrieved from https://graduateway.com/observations-of-chemical-changes/

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