This activity is designed to help students develop an understanding that time is not an "absolute." That is, a minute is something that is neither a long amount of time or a short amount of time, but merely a unit of time. So if you have a minute and have to zest a lemon, well, a minute is a long time. But it you have a minute, and have to prepare an skillet of caramelized onions, well, that's just not enough time. Incidentally, I doubt any of your students will come up with these examples.
My students really enjoyed doing this activity, because it gets to their intuitive understanding of time: that our perception of time is entirely dependent on the activity that is taking place. They have fun brainstorming the different activities that "feel" like a long time (an hour in traffic, a minute waiting for a friend to arrive for a playdate, etc.) and activities that feel like a short amount of time, like a minute playing a video game or an hour for a play date with a friend (which I'm sure the parents feel like goes a lot slower.....)
I've included a sample for you to look at. This is a great activity, you can do it in about 30 minutes, and it will get your kids writing about math!