Observations of Chemical Changes

Topics: Chemistry, Chemical reaction, PH Pages: 6 (2221 words) Published: July 8, 2013
Experiment 1: Observations of Chemical Changes

Abstract:In the lab 1 experiment, the objective was to observed properties of various chemical reactions between twelve different basic compounds. Each reaction revealed chemical properties consisting of color change, CO2 gas formation, and/or precipitate formation. Certain reactions made it possible to distinguish between an acid and a base. Through the results of this experiment, chemical properties observed in the reactions could be used to associate similar chemical substances and properties in household products. Experiment and Observations:The first step in this experiment was to sequentially pair basic compounds together and observe the chemical changes produced. Twelve compounds were paired together to produce eleven different results, successively labeled parts “A” through “L” (to exclude part F). The experiment was conducted by placing two drops of a substance in one well of the well-plate-96 followed by two equal sized drops of a second substance to produce an observable reaction (or lack thereof). Exceptions included part C where one drop of BTB (bromthymol blue) was used and part E where an additional drop of HCI (hydrochloric acid) was added to blue dye and NaOCI (sodium hypochlorite). In part K, the AgNO3 (silver nitrate) and NaOH (sodium hydroxide) mixture was saturated into a paper towel and exposed to a bright light. The resulting mixtures were then observed against two different backgrounds, one white and one black, by slipping a white piece of paper underneath the mixture and then doing the same with a black piece of paper. Observations were made for both backgrounds and recorded on a data table. In general, light colors and precipitates were easier to see against the dark background, and darker colors were easier to see against the white background. Data Table 1: Observations of Chemical Reactions

Chemicals| Well#| Reaction on White Paper| Reaction on Black Paper| NaHCO3 + HCI | A1| Formed CO2 gas bubbles| Formed CO2 gas bubbles, easier to see gas bubbles| HCI + BTB| A3| Turned yellow-orange| Turned yellow-orange, | NH3 + BTB| A5| No reaction, assumes blue color of BTB| No reaction, assumes blue color of BTB| HCI + Blue dye| A7| Turned dark green | Turned dark green | Blue dye + NaOCI (+ HCI)| A9| Turned dark blue, then green after HCI was added | Turned dark blue, then green after HCI was added | KI + Pb(NO3)2| A11| Turned bright yellow, thick| Turned bright yellow, able to see solid particle formation near bottom| NaOH + Phenolp..| C2| Turned bright pink| Turned bright pink | HCI + Phenolp..| C4| Turned milky, but remained clear| Turned milky, but remained clear | NaOH + AgNO3| C6| Turned brown, thick| Turned brown, able to see solid particle formation near bottom| AgNO3 + NH3| C8| Remained clear in well, turned pink on paper towel under bright light| Remained clear in well, turned pink on paper towel under bright light| NH3 + CuSO4| C10| Turned light blue, looks thick| Turned light blue, easier to see thickness |

The following observations were made starting with the combination of NaHCO3 (sodium bicarbonate – baking soda) and HCI in part A. When HCI was added to NaHCO3 the two liquids produced CO2 (carbon dioxide) in the form of gas bubbles. The CO2 gas bubbled up to the surface of the mixture for approximately one minute then stopped. In Part B, BTB was combined with HCI, an acidic substance, producing a yellow-orange liquid. In part C, one drop of BTB was added to NH3 (ammonia), a base, which produced a blue color, no real change. In part D, blue dye was added to HCI rendering the mixture dark green in color. In Part E, NaOCI reacted with blue dye creating a blue mixture, then one drop of HCI was added to the mixture and the color turned green. In part G, Pb(NO3)2 (lead nitrate) was added to KI (potassium iodine) forming a bright yellow precipitate. The solid form was more...
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