質量 しつりょう保存 ほぞん法則 ほうそくじゃなかったです
shitsuryōhozonno hōsokujanakattadesu

Noun
Desu Copula

The polite, past negative form of 質量保存の法則

1. It wasn't the law of conservation of mass.

Past/Perfective
Negative
Polite
Casual Register