Questions:
- What is the pH of the liquid?
- What are the properties of the red substance? Is the red substance harder than iron?
Hypothesis:
- I think the pH of the liquid is acidic because it was able to break down the foil, and also that two major elements that were included in the experiment were hydrogen and chlorine, the components of HCl, or hydrochloric acid.
- I think that the red substance is not harder than iron because compounds like copper chloride become oxidized when water is added, and a rusted compound is not as hard as a non-oxidized element.
Results:
Initial reaction:
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CuCl2 – Green, rocky powder (crystals)
Mixture – Water becomes blue and powder dissolves on contact, particles on bottom
- Al – Shiny, metallic, pieces easy to rip
Temp – Liquid is 20.9° C
Adding Al – Water becomes darker, begins to bubble, black pieces float in the eater, Al looks burnt, becomes red balls
Experiment #1
- The pH strips are yellow-orange in color
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After dipping the 1st strip in the liquid for one minute, the color changed to a slightly darker orange, indicting a pH between 4 and 5
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After dipping the 2nd strip in the liquid for one minute, the color changed slightly to a darker orange, indicating a pH between 4 and 5
Experiment #2
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1st day – Separated red substance from liquid, red substance looks grainy, leaves a trail of red particles
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2nd day – Used iron filings to test the hardness of the red substance
– Removed the red substance from filter paper, looks fragile, can be compared to hardened sand
- Put filings in a pile then tried to crush them with the red substance
- Red substance broke apart easily, formed a powder
- The red substance is not harder than iron
Discussion:
The objective of this lab is to understand the property of a chemical reaction and to create reasonable testable questions to predict the outcome of the reaction with scientific inquiry. During the initial reaction involving the aluminum foil and the copper chloride, the emergence of the red substance led to two testable questions to determine the physical and chemical properties of the substance. The testable question “What is the pH of the liquid” helped determine the acidity of the liquid to explain the decomposition of the foil into the red substance. “What is the hardness of the red substance in relation to iron?” proved that the substance is not iron.
The pH level of the liquid is acidic because it was able to break down the foil and two major elements included in the experiment were H and Cl, the components of hydrochloric acid. The liquid did turn out to be acidic. However, it was not HCl, for the pH was too high. HCl usually ranges between 0 and 2, and the liquid had a pH of between 4 and 5. The sources of error could have possibly been that the liquid was far too diluted, and that the pH strips could have been contaminated.
The red substance is not harder than iron because compounds like copper chloride become oxidized when water is added, and a rusted compound is not as hard as a non-oxidized element. The red substance was indeed not iron and it is believed to be rust. The properties of water act as a catalyst that speeds up the reaction. Rusting naturally would take years instead of hours. Possible errors include not having pure iron filings and the red substance not being completely dry.
The experiments done by other groups included testing the red substance’s flammability, the liquid’s flammability, testing for density, pH, and solubility. The flame test proved that the red substance was a compound of both aluminum and chlorine with additional copper, or copper and aluminum with additional chlorine. However the density tests proved nothing, since none of the densities were similar to each other or the density of the possible compounds. The pH was determined to be around 4 or 5, as all groups who tested pH had very similar results.
It can be determined that the red substance is either the compound CuAl + Cl or AlCl + Cu through various stages of scientific inquiry. After narrowing the possibilities by conducting various tests, the products and their exact grouping can only be determined by testing for more chemical and physical properties. Finding the color of the substances for the two groupings as well as the state of matter will ultimately determine the composition of the red substance.
