Unsaturated carboxylic acids like acrylic acid have the formula CH2=CHCO2H. This liquid is clear and colorless, and it smells strongly of acid. As it includes a polar carboxylic acid functional group, it is able to dissolve in water and is miscible with comparably polar organic molecules such as alcohols, ethers, and chloroform. In the presence of acids, alkalis, amines, peroxides, and iron salts, it may polymerize. Polymerization can also be brought on by extended exposure to heat or light. Even at room temperature, the polymerization of acrylic acid can cause an explosion if it is restricted. It is corrosive to metals and tissues.