Put iron expand when it is heated in the passive voice
Iron is expanded by heat.
http://grammar.about.com/od/pq/g/pasvoiceterm.htm
In order to rewrite the sentence "Iron expands when it is heated" in the passive voice, you need to rephrase it to emphasize the receiving of the action rather than the doer of the action. Here's how to do it:
"The expansion of iron occurs when it is heated."
To convert this sentence into the passive voice, we:
1. Started with the original active sentence: "Iron expands when it is heated."
2. Identified the subject (iron) and the verb (expands).
3. Moved the object (iron) to the beginning of the sentence.
4. Changed the verb (expands) to a passive form (occurs).
5. Moved the original subject (it) to the end of the sentence, preceded by the preposition "when."
By following these steps, the sentence is rewritten in the passive voice.