Tuesday, July 5, 2011

Lab Report: Metal or Nonmetal Lab

Abstract:

For this lab experiment, our new group, The Acids, tested sample elements A-G with the hopes in gaining enough knowledge to characterize each sample as a metal, a nonmetal, or a metalloid. To prepare for the simple, yet tedious procedure, we placed each of the seven elements on a piece of paper, and labeled them to prevent confusion. Then, after recording the initial appearances of each sample on our data table, we were ready to begin the procedure that required plenty of focus and copious notes. The process included observing appearance, conductivity, crushing, reactivity with copper (II) chloride, and reactivity with hydrochloric acid. We entered the experiment with the knowledge that metals have a luster, are malleable, and conduct electricity, nonmetals are usually dull, brittle, and do not conduct electricity, and metalloids have some properties of both. After crushing each sample on our piece of paper, and then labeling and filling our wellplate with each sample twice, Rachel used the electrical conductivity apparatus to test the conductivity of each sample. Then, we added 20 drops of copper (II) chloride to the left well of each set, and 20 drops of hydrochloric acid to the right well of each set. After about three minutes, we analyzed whether or not there was a reaction, and what kind of reaction occurred in each wellplate. Then, we recorded the data in our data table. Although it was difficult deciphering those elements that possessed contradictory physical and chemical properties, we analyzed our detailed data table and, with our knowledge of the three categories, came to the conclusion that sample elements B and G were metals, sample elements A and E were nonmetals, and sample elements C, D, and F were metalloids.

Procedure:

Even before beginning the procedure, our group, The Acids, spent more time than other groups to organize our notes, data table, element samples, and labels with the motive of conducting a quick, smooth, and accurate experiment. First, we gathered all the tools needed to begin the experiment: two plastic wellplates, a notebook, a pen, a piece of paper, scotch tape for labeling, a hammer-like object, copper (II) chloride, and hydrochloric acid. Then, we waited as Rachel distributed sample elements A-G to each lab group. Before crushing the elements, we waited until all samples were placed on our piece of paper and labeled with their corresponding letters.
We also ripped pieces of scotch tape in half, and labeled two of the same letter on each piece; we attached these pieces of tape to the wellplates, assigning the same letter to each set of two wells. After we were sure we had everything organized, we documented the initial appearances of each sample onto our data table very carefully and in great detail to ensure accurate results. From the data of the appearances alone, sample A appeared to be nonmetallic, samples B and C appeared to be metallic, and samples D, E, F, and G were undecided. Once we were sure everything was organized, we were ready to crush each sample element to decide whether they were malleable or brittle.
Since sample A was originally a powder and remained a powder, samples C , E, and F were brittle, and sample D was very hard to break and sort of brittle, we recorded them as nonmetallic. Because sample B was clearly malleable, we recorded it as a metal. Due to brittleness, yet shiny and hollow chambers revealed in sample G, we recorded it as undecided. After crushing, we divided each sample element in half and placed them side-by-side in the wells in the labeled wellplate.
Rachel tested each crushed sample element’s electrical conductivity with the electrical conductivity apparatus; even if the light bulb was only slightly lit, the light indicated electrical conductivity.
Sample elements A and E were not conductive and sample elements B, C, D, F, and G were conductive—metals conduct electricity. Next, we were ready to fill the wells with copper (II) chloride and hydrochloric acid. We decided to fill the left well of each set with copper (II) chloride, and the right side of each set with hydrochloric acid. After placing 20 drops of each into the wells, we had to wait for a reaction (if any) for three to five minutes.
After three minutes, we analyzed each well set. On the copper chloride side of each sample, the left side of each set, we observed that the liquid simply sat in a pool around each sample for all samples except for sample G. In copper (II) chloride well G, the sample turned black, and a black substance began to come off of the sample. With this data, we recorded only sample G as metallic. On the hydrochloric acid side of each sample, the left right side of each set, again, the liquid sat in a pool around each sample. This time, there were two exceptions in hydrochloric acid well D and, again, well G. The reaction in well D was not very prominent, but we noticed that some bubbles formed in the clear liquid around our sample. In well G, we noticed many bubbles coming off and popping off of our sample that appeared to be dissolving. From this data, we concluded that samples D and G were metallic.
After making sure we had all of our notes down and data table complete, we cleaned up our supplies and went on to analyze the properties of each sample element to reach a conclusion as to what was metallic, nonmetallic, or a metalloid.

Results:

Although this lab may seem simple, our group had some trouble classifying our cumulative data into metal, nonmetal, or metalloid. The metals and nonmetals were very clearly shown in our results from the five observations we produced, but due to contradicting properties, the metalloids were not. Just looking at the initial appearance of our samples to decipher if each sample was a metal or nonmetal was complicated because many samples such as D, E, F, and G contained small particles of shiny bits, or tiny specs of luster. Drawing conclusions from just appearance would often lead to inaccurate data, so we had to use our conclusions from the tests for electrical conductivity, crushing, and chemical reactions with copper (II) chloride and hydrochloric acid as well. Since a lot of the data per sample was contradictory, it made it difficult to decide what category each fit into. In addition, the concept of deciding how a sample could be a metalloid was very unfamiliar to us, so we had to review in our book that although metalloids have properties intermediate to metals and nonmetals, sometimes the absence of a property that defines a metal or nonmetal does not alienate it from being part of one of those categories. After difficult analysis, we concluded that element samples C, D, and F were metalloids, element samples A and E were nonmetals, and element samples B and G were metals.

Data Analysis:

1.Classify each property tested in this investigation as either a physical property or a chemical property.

Appearance: Physical property
Conductivity: Physical property
Crushing: Physical property
Reactivity with copper (II) chloride: Chemical property
Reactivity with acid: Chemical property

2. Sort the seven coded elements into two groups based on similarities in their physical and chemical properties.

1st Group: (Metals) B, G
2nd Group: (Non-Metals) A, C, D, E, F

3. Which element or elements could fit into either group? Why?

Elements C, D, and F could fit into either group—metalloids. These elements could be metalloids because although some of them did or did not show to posses conductivity, some were brittle and did not react with either acid solution, and some did. Because these elements were contradictory in their cumulative results for the tests, they could be classified as metalloids.

4. Using the following information, classify each tested element as a metal, a nonmetal, or a metalloid:
-Metals have a luster, are malleable (can be hammered into sheets), and conduct electricity.
-Many metals react with acids; many metals also react with copper (II) chloride solution.
-Nonmetals are usually dull in appearance, are brittle, and do not conduct electricity.
-Metalloids have some properties of both metals and nonmetals

Metals: Elements B and G.
Nonmetals: Elements A and E.
Metalloids: Elements C, D, and F.

Data Table:

Conclusion:

After having a class discussion, we discovered that we were accurate in almost all of our conclusions based on our data, with two exceptions. We discovered that element A, that we classified as a nonmetal, was aluminum (Al), a metal. This mistake occurred because aluminum is right on the edge of the break between metals and nonmetals, above some metalloids. Because of its closeness to the nonmetals on the periodic table, our mistake in confusing aluminum, a metal, for a nonmetal, was not uncommon. Additionally, the aluminum sample was in powder form, and powder rarely conducts electricity. Our second mistake was with element sample F, Carbon (C). On the periodic table, carbon is a nonmetal, but we classified it as a metalloid. Because carbon conducted electricity but was brittle and did not react with either copper (II) chloride and hydrochloric acid, we thought that since metals conduct electricity, it would be a metalloid. Now we realize that even though carbon conducts electricity, it is a nonmetal. Despite these two errors, we were correct in our conclusions for sample elements B, C, D, E, and G: element B was tin (Sn), a metal, element C was Silicon (Si), a metalloid, element D was Antimony (Sb), a metalloid, and element G was zinc (Zn), a metal. Overall, this lab experiment was very helpful in understanding the differences between metals, nonmetals, and metalloids, and how to characterize elements based on experiments.

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