Acrylic acid (C₃H₄O₂) is a clear, colorless liquid and the simplest unsaturated carboxylic acid. It is highly reactive and versatile, primarily serving as a vital chemical intermediate. Acrylic acid is corrosive to metals and human tissue in both its liquid and vapor states. Because it is highly susceptible to heat-induced self-polymerization, which can cause closed containers to rupture, it is typically transported and stored with a polymerization inhibitor such as hydroquinone.