Answer:
A physical change
Explanation:
A physical state is one that alters the physical properties of matter. In most cases physical changes are easily reversible. The physical properties of matter shows everything about a matter when no change is occuring to it.
When writing on a chalkboard, the state of matter is barely changing from a solid mass of chalk to a powdered form which can easily mark the board.
No change is occuring to the board besides the colour marking it which can easily be erased.
Physical changes can easily be reversed using seperation techniques, in this case, merely wiping the board.
To show that no chemical change has occur, no new kind of compound is formed when marking the board. We can easily collect the powdered chalk back.
