Yes, CHEMICAL is a Scrabble word!

Letter values in Scrabble US: C 3, H 4, E 1, M 3, I 1, C 3, A 1, L 1.

Is it a valid word?

CHEMICAL is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

material produced by or used in a reaction involving changes in atoms or molecules

relating to or used in chemistry
of or made from or using substances produced by or used in reactions involving atomic or molecular changes

Also: chemical substance.