They both can be used as an example for thixotropy! Thixo… what?!?Thixotropy could in simple terms be called the effect of a fluid to be even more „liquid“ after shaking it. With ketchup thats quite easy to show. Try to pour it out before and after you shook the bottle (should be a glass one for better visibility of the effect).
What about the coffee? Use a spoon to stir it up and then repeatedly knock to the bottom of your cup. The pitch will degrade while the coffee stirs slower and slower.
While I consider the latter funny, the ketchup thingy might at least be useful…