There are occasions when we might want to use passive verbs, such as when we don’t want to mention the doer, the result of the action is more important than the doer, or the doer is unknown. Let’s take the following scenario and apply it to all three reasons for using a passive verb.
Tom and Mark, two brothers, are preparing their home for the zombie apocalypse. Tom is throwing canned goods across the room to Mark, who is stacking them on a shelf. They continue to throw canned goods across the room, despite knowing that it’s against their mother’s wishes. Tom throws a can of creamy corn to Mark and accidentally hits a vase. The vase breaks into pieces. Their mother asks what happened.
The responses could go as follows:
The vase was broken when the creamy corn was thrown at it.
The first sentence uses the active verbs threw and broke. It simply tells what happened and squarely blames Tom. The second sentence uses the passive verbs was broken and was thrown. It doesn’t mention who threw the can of corn, keeping the doer unknown. Also, it might be reasonable to believe that Tom thinks letting his mother know that the vase is broken is more important than identifying who broke the vase.
Of course, in the grand scheme of things, what is a vase in the face of a zombie apocalypse, but you get the idea!