Help needed: Past participle practice!

[Kelly Farrow]

Hi! I'm teaching English in Japan and could use a little guidance. The middle school third years (like freshmen in the U.S.) are learning the past participle when used as an adjective, like this:

The language spoken in England is English.

One word used in math class is cosine.

I received a letter written in Chinese.

I find this to be a bit of an abstract concept and probably not all that important in everyday speaking, but hey, what can you do?? (In Japan, you really have to follow the curriculum!!) Has anyone taught this before? Any ideas or suggestions for an activity that can reinforce this usage for the kids?

Thanks!!