Abstract
The aim of this laboratory exercise is to present a high school hands-on laboratory experiment, focused on obtaining and investigating the properties of various polymorphic forms of aluminum oxide. Amphoterism plays a key role when discussing the law of periodicity and periodic changes of acid–base properties of elements and their compounds. In many school syllabuses, that issue is based on third period elements, so the amphoteric substances are aluminum, aluminum oxide, and aluminum hydroxide. Although demonstrating those properties for aluminum and aluminum hydroxide is relatively simple, the same reactions for alumina can be quite problematic. It is due to the fact that aluminum oxide exists in several polymorphic forms, and only one of them reacts with acids and bases. Moreover, the commercially available aluminum oxide materials are usually nonamphoteric. The exercise describes preparation of various polymorphic forms of aluminum oxide by thermal decomposition of aluminum hydroxide, and tests for its...
Published Version
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