Lab 3 REPORT FORM Do You See the Light_F22

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Purdue University *

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115

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Chemistry

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Jan 9, 2024

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Lab 3: Do You See the Light? REPORT FORM Answer the following discussion questions. Support your claim using evidence, i.e., experimental data and/or observations that support the claim. Cite specific quantitative results (i.e., time duration of luminescence). Connect your evidence (data and/or observations) to your claim using reasoning that explains why your evidence supports your claim. Reasoning should be based on a scientific rule, law, principle, or definition. Question #1. What are some indications of a chemical or physical change you’ve observed in step 1? Explain your reasoning. Question #2. What are some indications of a chemical or physical change you’ve obse rved in step 2? Explain your reasoning. Indications of a chemical or physical change I observed in step one was color change when we heated the combined nitrophthalic acid and aqueous hydrazine. It started to change to yellow at first and then changed to a dark reddish brown as we continued to heat the mixture. As we continued heating our mixture, I noticed that other groups ’ mixtures were not the same color as ours. Ours didn ’ t seem like it was melting at first, but it eventually did, taking much longer than any other groups. The color changes were an indication that a chemical change happened. Indications that there was a physical change was when the mixture turned to a thick paste once cooled down and put through filtration. I noticed that the other groups were more of a powder and not a dark reddish-brown color. Due to heating the mixture at least 30 degrees Celsius over the intended temperature it most likely caused a chemical change which explain why ours was so different. This hypothesis was formed from a discussion me, and a peer had with Dr. McLuckey on why our mixture did not light up. Indications of a chemical or physical change I observed in step two was once again color change from a dark reddish brown to a mustard brown. When a yellow precipitate, luminol, should have formed ours separated into a mustard brown and a dark brown substance which indicates a chemical change.

Question #3. How long did your chemiluminescence persist? What are some factors that might have contributed to the length of this phenomenon? Explain using your observations. Question #4. Describe the intensity of your chemiluminescence. What could have increased/decreased the intensity of the glow? Explain using your observations. Our group did not achieve chemiluminescence since we heated the mixture 30 degrees Celsius than we should have. Since ours did not light up we asked other groups and their answers ranged from 5 to 30 seconds. A possible explanation is that the hydrogen peroxide degrades. When hydrogen is exposed to light and air, it degrades into water. This means that the groups who had lab first most likely lasted the longest. Our group did not achieve chemiluminescence since we heated the mixture 30 degrees Celsius than we should have. Since ours did not light up we asked other groups and their answers revealed that when they added the luminol to hydrogen peroxide and the potassium ferricyanide, the mixture glowed a bright blue and either very quickly or soon after it dulled into a lighter blue glow which was less intense. The intensity of the glow could have been more intense if the prior mixtures were the purest possible. Evidence is that it glowed more intense at the beginning versus the end (when it was less pure).

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