Observation of Chemical changes Essay
Observation of Chemical changes
Abstract: The purposes of this lab is to observe the reactions of some common chemicals contained in consumer products and observe the macroscopic changes these chemicals undergo. Purpose: The purpose of the lab is to be able to interpret underlying macroscopic changes in terms of the behavior of atoms and molecules and also to learn how to separate mixtures into their component substances by solubility.
1 Sheet of white and dark paper
1 Paper towel
1 Distilled water
1 Small amounts of household cleaning products
1 Pipet, Empty Short Stem
1 Aqueous Ammonia, 1M -1mL
1 Bromthymol Blue, 0.04% – 2 mL in Pipet
1 Copper (II) Sulfate, 0.2 M – 2 mL in Pipet
1 FDC Blue Dye #-1.0.1% – 2 mL in Pipet
1 Hydrochloric Acid, 1.0M-1 mL
1 Lead (II) Nitrate, 0.2 M- 2 mL in Pipet
1 Potassium Iodide, 0.1 M-2 mL in Pipet
1 Silver Nitrate, 0.1 N – 2 mL in white Dropper Bottle
1 Sodium Bicarbonate, 1 M – 2 mL in Pipet
1 Sodium Hydroxide, 1 M – 1 mL
1 Sodium Hypochlorite, 1% – 2 mL in Pipet
1 Starch Solution, 1% Stabilized – 2 mL in Pipet
1. For the following combinations of chemicals and using a different well of the 96-well plate for each combination, place 2 pipet drops of the first in one well and add 2 drops of the second chemical. Next observe the mixtures against the white and dark backgrounds by slipping white and black paper underneath the well plate. For each reaction record the well number of the mixture and your observations.
a. Sodium Bicarbonate and Hydrochloric Acid
b. Hydrochloric Acid and Bromothymol Blue
c. Ammonia and Bromothymol Blue
d. Hydrochloric Acid and Blue Dye
e. Blue Dye and Sodium Hypochlorite
f. Potassium Iodide and Lead Nitrate
g. Sodium Hydroxide and Phenolphthalein
h. Hydrochloric Acid and Phenolphthalein
i. Sodium Hydroxide and Silver Nitrate
j. Silver Nitrate and Ammonia
k. Ammonia and Copper Sulfate
Data and Observations:
Sodium Hydroxide and Silver Nitrate
Silver Nitrate and Ammonia
Ammonia and Copper Sulfate
Hint of pink when silver added looks like brown mud
Sediment layer baby blue with dark layer on top.
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?
You would mix it with HCI and observe it for bubbles.
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 household items including household cleaning products with Bromothymol. Name the items tested and record their results. What do these results mean?
Bleach with Bromothymol Blue – Yellow and blue layer/ it separates the acid and the base.
Hand Soap with Bromothymol Blue – Turned yellow which means it’s an acid.
Ammonia with Bromothymol Blue – Dark blue which means it’s a base.
C. You found a sample of a solution that has a faint odor of vinegar. You are verifying that is indeed vinegar and you add a few drops of phenolphthalein. The sample turns pink. What assumption can you make about this sample.
When turning pink it would mean it was a basic solution meaning the solution isn’t vinegar because vinegar is an acid.
D. You decided to investigate if the new wave of vitamin water is pH neutral: neither to acidic nor to basic. Using 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 slight yellow, while one remains blue. What can you assume about the acid/base content of these particular flavors of Vitamin Water.
You could assume that the three were neutral, the more yellow solution was more acidic and the blue solution was basic.
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.
You could add potassium iodide and if there is lead it will precipitate.
Results/Analysis: The objective of the lab was to observe the macroscopic changes that occur in chemical reactions and attempt to interrupt the macroscopic changes of the atoms and molecules that allow for the macroscopic changes to happen. This taught me how to distinguish between acids and bases, how to differentiate between one chemicals reaction to many different other chemicals when added together and what these reactions mean. Errors that could have occurred were that the drops of chemicals could have easily been different sizes, which could have made the reactions different than if everything was an even ratio. Although since we were using such small amounts of each of the chemicals I feel the reactions were quit normal.
Except for the silver nitrate and ammonia, there wasn’t any reaction that was recorded because I feel we didn’t use enough chemicals. We used our observations from another lab group whose paper turned brown after some time under a light. This error could have occurred because we didn’t hold our tissue closer to the light bulb or long enough.
Conclusion: This lab experiment forces an individual to think critically as to what macroscopic changes are occurring and why they are occurring. It taught us the difference between acids, bases, and neutrals, also if two specific chemicals are mixed together such as, potassium iodide and lead nitrate it will take on a precipitate form. I also learned how important ratios are in an experiment. If one chemical is greater than another, than a completely different reaction can occur than expected. With this said it is also important for us to learn how to separate mixtures into their component substance and solubility. If specific chemicals for example, HDI were greater in ratio than the reactions could have turned out much different. All in all, the entire lab was presumably helpful and a great introduction for what’s to come in class.