Experiment : Observations of Chemical Changes

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Title and Identifiers: Observations of Chemical Changes by the use of acids and bases. Abstract: To observe the small changes that occur in chemical reactions and attempt to interpret the changes of the atoms and molecules that allow for these small changes to happen; and to associate these chemical properties with household products. We will also learn how to separate mixtures. Experiment Procedures: 24-well plate is used as a convenient holder for the pipets of chemicals. 96-well plate is used for mixing the chemicals. For each combination, a different well is used. For each combination, 2 drops of the 1st chemical are placed in the well followed by 2 drops of the 2nd chemical. After placing 2 drops of the 2nd chemical, observation is immediately made for any change of color, forming of precipitates or bubles. Also white & dark backgrounds are alternatively placed underneath the well plate for observing the mixture. Then the information is recorded into data book. Data Table 1: Reactions Expected Well # Chemicals Reaction A1 NaHCO3 and HCI - C02 Clear bubbles/bleach smell formed. No color change. A2 HCI and BTB Turned to amber orange A3 NH3 and BTB Turned to dark blue A4 HCI and blue dye Turned to green A5 Blue dye and NaOCI Color stays blue and not change until 1 drop of HCl added then color turned to light yellow A6 NaOCI and KI Turned from dark yellow to light yellow. Precipitate is seen but gradually gone. Add 1 drop of starch. Turned to black. This test was also performed on various foods to cofirm the presence or absence of starch: Apple: turned to yellow Banana: No change of color Potato: turned to yellow Different cookies: turned to yellow or black A7 KI and Pb(NO3)2 Turned to yellow with milky white precipitate A8 NaOH and phenolphthalein Turned to light purple when seen on white background and dark purple on dark background

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