Zinc is a metallic, bluish-white metal that is brittle at room temperature but becomes malleable when heated. It is used for many purposes, including galvanizing steel to protect it from rust; making brass; coating wire and other components; and in medicine and cosmetics. zinc granules are a form of the metal that is finely ground and more convenient to use than the chunky pieces of pure zinc. The granules are able to react more quickly with hydrochloric acid than pure zinc can due to its smaller particle size.
Pure zinc can be obtained by smelting it from its ores or from a zinc concentrate. To produce pure zinc from concentrates, it must be remelted in a special bath to separate out the iron-containing material called zinc dross. Once removed from the dross, the pure zinc is mixed with other elements such as aluminum to produce a mixture called the zinc blende. The zinc blende is then melted in a crucible to make pure zinc ingots.
When the ingots are exposed to hydrochloric acid, they react to form zinc chloride and hydrogen gas. This reaction is known as a single replacement reaction. The granules react more rapidly than pure zinc can because they contain copper, an impurity that acts as a catalyst and speeds up the rate of reaction. This is why zinc granules are preferred for laboratory preparation of hydrogen compared to the use of pure zinc powder.