Q.1040: Why it is easier to erase a pencil mark than a pen (ink) mark on paper?
Ans. Graphite in the pencil create mark on paper. The graphite attachment/bonding to the paper is only physical. The affinity of graphite is more to eraser than paper, making it easier to remove a pencil mark from paper.
On the other hand, pen ink is liquid and penetrate in to paper body. The ink attach to paper by physical as well as chemical bonding, making it very difficult to erase.