Cleaning dry impurity from the floor

Q: My question is regarding concrete floor and impurity. I know for a fact that some dry impurity fell on the concrete, so I wiped it once with a dry piece of tissue (and should have left it there). But for some reason I had poured water on it and it went underneath the basin of the bathroom. If I tried my best to soak up the water with tissue, would it be considered clean. Keeping in mind I poured water on it once. I was in a hurry because others needed to use the w/c.

Overeating

Q: If I make a close relative food and it is a plateful of food surpassing what they require, will I be sinful if they eat more than their fill? Because I feel that they would rebuke me for giving them less, but I have already explained to them about overeating. What shall I do?