Question

When a crystal of copper sulphate is placed at the bottom of a beaker containing water, the water slowly turns blue. Why?

Answer 1

When a crystal of copper sulphate is placed at the bottom of a beaker containing water, the particles or molecules of copper sulphate start diffusing into the particles or molecules of water. The particles of water have large inter-molecular spaces between themselves, which are slowly occupied by the particles of copper sulphate; thereby, turning the water blue.