Here is a context clues worksheet on the noun cusp that might be of use in you classroom. It’s a solid abstract noun that has a foot in the concrete world, which may make it suitable for teaching the difference between concrete and abstract nouns.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.