<center><b>Nominative, Accusative, and Dative: When to Use Them</b></center>

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A metal is an element that forms, in most cases, a salt and hydrogen with an acid and a salt and water with an alkali. Almost all metals are hard, solid, opaque and are good conductors of heat and electricity. (Mercury, which is liquid at normal temperatures, and sodium, which is soft, are exceptions.) Metals are usually divided into two main groups, base metals and noble metals. Base metals are metals like iron, tin and zinc that we use to make everyday equipment. Gold and silver, for example, are noble metals that we use mainly for expensive ornaments, coins and jewellery. In engineering, we divide base metals into two other groups, light metals (like aluminum and magnesium) and heavy metals (like iron and lead). Alloys are a mixture of a pure metal with other pure metals or with non-metal chemicals such as carbon. Alloys are made by mixing the molten substances and then cooling them until they solidify. Common alloys are steel (iron + carbon), brass (copper + zinc) and aluminum alloys (aluminum + copper, aluminum + magnesium). Although metals and metal alloys are still the most important material in engineering, we now use plastics in many light applications to save weight.