Four students (A, B, C, and D) are given separate solid samples of the same unkn

Question

Four students (A, B, C, and D) are given separate solid samples of the same unkno They are asked to determine whether the substance is a metallic element, a ionic compound. In order to find out, they independently carry out experiment properties of the substance. Student A observes the sub-stance to determine itsmine solid's ability to conduct electricity. Student C determines whether the solid is Student D determines its melting point and tests the melted liquid's ability to students do not communicate their separate findings to one another. The results of shown in the table below. Use t Applying Scientific Methods wn pure substance out experiments to determiner #bleandductile. whether the solid is malleable a B tests the of their experiments are he information to answer the questions that follow. Property Studied Result Student B Ability of solid to conduct electricity C Malleability and ductility Nonlustrous Nonconducting Nonmalleable and nonductile Critey Approximately 800°C Melting point Good D Ability of melted liquid to conduct electricity 1. On the basis of his results, Student A concludes that the solid is a nonmetallic element element or an ionic compound. Comment on the soundness of his conclusion, rather thana given only what he has determined about luster 2. On the basis of her results, Student B also concludes that the unknown is a nonmetallic element Evaluate her conclusion. . On the basis of his results, Student C concludes that the unknown is a metallic element. Evalute conclusiorn.

Explanation / Answer

Both non-metallic and ionic compounds can be non-lustrous. Ionic salts, for example, are non-lustrous. Even metals loose their lustre due to an oxide layer formed on the surface due to oxidation. Thus, it is wrong to conclude that the material is nonmetallic solely based on its lustre. Student B's conclusion is somewhat logical, because even tungsten, which has one of the lowest conductivities among metals, conducts to a certain extent. So, as long as "non-conducting" means almost zero conductivity, B's conclusion is fairly accurate. Student C's conclusion is fallacious. Almost all metals, except zinc are malleable and ductile. Thus, chances are very high that C's conclusion would be proved wrong. Student D's conclusion is correct, because 800degrees celsius is very ambiguious. metals have melting points in the range of room temperatures (Gallium) to thousands of degrees. Ionic compounds too have melting points in this range. Thus, it is not possible to predict the type of material from its melting point alone. B and C's results together strengthen B's conclusion that the material is non-metallic. But since C wrongly believes that the material is metallic, they may have an argument, Nonetheless, they would eventually conclude that the material is non-conducting. D's observations are not very helpful, therefore, it would add any value to what B had already concluded. It may help. Ionic compounds would dissolve in water thus we can atleast state whether the material is ionic or not. This illustrates that before drawing conclusions, we should conduct many different experiments and consider the results of all those experiments before concluding anything.

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