V + 成【chéng】

成 after a verb is a result complement – a word after the verb that says how it turned out. 成 says what the thing became: the verb is the action, and the noun after 成 is the result.

Because the object is changed into something else, 把 is the usual frame: 把 + object + verb + 成 + result.

Mistaking A for B

With 看, 听, 写 and 当, V成 can mean taking one thing for another by mistake.

Keep the 成

"Into" with a change of form is 成. 到 is for reaching a place or a point, and a bare 变 + noun has no result in it.

• × 把这本书翻译到中文 → 把这本书翻译成中文
• × 他变了一个老师 → 他变成了一个老师

Where 了 goes

了 follows the whole verb + 成 unit, not the verb alone.

• × 水变了成冰 → 水变成了冰