Hot water effects

Today, my roommate had yet another interesting experience. She was washing dishes in the sink and had really hot water coming out of the faucet. She left a cup made out of something very muck like plastic under the running hot water. After a few minutes, it popped.  What probably happened was that the hot water expanded the molecules in the material to the point where it could not resist it anymore and it finally released the tension by "popping".