Ethanol can be dehydrated to give ethene by heating it with an excess of concentrated sulphuric acid at about 170°C. Concentrated phosphoric(V) acid, H3PO4, can be used instead. The acids aren't written into the equation because they serve as catalysts.
When a substance undergoes a chemical transformation, its chemical identity changes. Rust is one illustration of this. An iron nail rusts, turning brown-red, when it comes into touch with water and is then exposed to air. The chemical makeup of the original material is altered throughout this process.
Examples include the reactions of iron and oxygen to produce rust and vinegar and baking soda to produce sodium acetate, carbon dioxide, and water.
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