IGCSE Chemistry topic 11, part 1 – Water:
http://www.youtube.com/watch?v=-BZKRLXapCY&feature=share&list=PLthIRQZYW9MLUwo1I3RGFCnzOy3CypB3
A short video form The Virtual School – testing for water:
Infographic from Compound Interest – just click to enlarge.