Question

when we write something in the board and erase it after a long time y it is very difficult to erase

Answer 1

The particles get a long time to be contact with the board and get stick to the surface of the bord

Answer 2

Answer: When we write something in the board and erase it after a long time,it is very difficult to erase,because the particles of the chalk disperses with the particles of the blackboard.This process is called the Dispersion of Solids.

Explanation: Hope that it helps you. Please mark me as the brainliest.