Question

What happens when chalk powder and sand are added to water and why?

Answer 1

Chalk is usually close to pure calcium carbonate. “Sand” is normally assumed to be quartz sand so almost pure silicon dioxide. The sand will sink to the bottom pretty quickly. The chalk will also mostly settle out but the finer grains may stay in suspension - prevented from falling to the bottom by random collisions with the water molecules. A tiny proportion of the chalk will dissolve and another tiny proportion may react with dissolved carbon dioxide (in the form of carbonic acid).

At the bottom of your container will be a layer of mostly sand together with a proportion of chalk and above tgat a layer of chalk.

Answer 2

Chalk is insoluble in water so when added the heavier particles settle down and finer particles form a suspension ...similar case with sand as u know heavy particles settle down whereas dust and other fine particles may mix with the water and hence result in change of colour (Brown )