caustic - Sarcastic or severely critical, often in a hurtful or biting manner; or able to burn or corrode organic tissue, typically referring to chemicals or substances.

The caustic chemical spilled onto the floor and quickly started to eat away at the floor surface.
semblance - The way something appears on the surface, often without revealing the true nature or reality behind it.

In spite of their their kids' constant uncontrolled behavior, when they were outside they managed to keep up the semblance of calm, even though things were not so calm inside their house.