Which substance has a very high pH and tends to burn deeper than acids, with potentially delayed pain?

• A. Acids
• B. Petroleum-based
• C. Alkalis
• D. Hydrocarbons

Answer: (C)

High pH indicates a strong base, which classifies it as an alkali. Alkalis burn tissue through liquefaction necrosis, where fats and proteins are dissolved, allowing the chemical to penetrate more deeply into underlying tissues. This deeper penetration explains why the injury can be more extensive than with acids, and why pain may be delayed—the surface may not feel severely damaged at first even as deeper tissues continue to be harmed. Acids, by comparison, tend to cause coagulative necrosis and form an eschar that can limit depth, often producing more immediate surface pain. Petroleum-based substances and hydrocarbons aren’t defined by a very high pH and typically cause irritation or burns through different mechanisms rather than deep liquefactive damage from strong bases.