Question

Due to which of the following reason marks of chalk could not be removed after a long time ?

• A. Paricles of chalk diffuse into the particles of blackbaord.
• B. Paricles of blackboard diffuse into the particles of chalk.
• C. Paricles of chalk condense onto the surface of blackbaord.
• D. Paricles of blackboard condense onto the surface of chalk.

Answer 1

The correct option is A Paricles of chalk diffuse into the particles of blackbaord.

As chalk is a solid and solids have a slow diffusion process. When we write on the blackboard using a chalk then the particles of chalk diffuse on the board and occupy the vacant spaces of the blackboard. So, when kept for a longer period of time the marks of chalk are unable to be wiped out easily.