Question

There are times when the night sky glows with bands of color. The bands may begin as cloud shapes and then spread into a great arc across the entire sky. They may fall in folds like a curtain drawn across the heavens. The lights usually grow brighter, then suddenly dim. During this time the sky glows with pale yellow, pink, green, violet, blue, and red. These lights are called the Aurora Borealis. Some people call them the Northern Lights. Scientists have been watching them for hundreds of years. They are not quite sure what causes them. In ancient times people were afraid of the Lights. They imagined that they saw fiery dragons in the sky. Some even concluded that the heavens were on fire.

Answer 1

Answer:

The process of deriving large crystals of pure substances from their solutions is known as crystallisation. It is a physical change. Crystals of salt are obtained by the evaporation of sea water. ... This mixture when filtered and allowed to cool produces crystals of copper sulphate.