化する【かする】

化 goes after a noun and means "-ize", "-ify": a change into that state. With する it is a verb; on its own it is a noun, "-ization". The noun in front is nearly always a kanji compound or a loanword.

Becoming and making

化する is a する verb, and many of them work both ways. Something that changes by itself takes が; something a person changes takes を.

Some describe only a change that happens by itself, like あっか悪化する and しんこく深刻かする化する. When a person causes the change, these verbs take the causative.

Nouns, not adjectives

化 goes on nouns. To say that something becomes more convenient or cleaner, an adjective takes きごう〜くなる or きごう〜になる, and きごう〜くする or きごう〜にする when someone makes it so.

• × 部屋をきれい化した → 部屋をきれいにした

Most 化 words sound like news or written Japanese. In conversation a plainer verb often does the job: あっか悪化した becomes わるくなった悪くなった.