Markets offering “organic” produce claim it has been raised “without chemicals.” News stories fret about “chemicals in our water supply.” This common error in usage indicates quite clearly the lamentable level of scientific literacy in our population. Everything on earth save a few stray subatomic particles and various kinds of energy (and—if you believe in it—pure spirit) is composed of chemicals. Pure water consists of the chemical dihydrogen oxide. Vitamins and minerals are chemicals. In the broadest sense, even simple elements like nitrogen can be called chemicals. Writers who use this term sloppily contribute to the obfuscation of public debate over such serious issues as pollution and malnutrition.
Quote from: http://www.wsu.edu/~brians/errors/chemicals.html
The site has other common errors in English usage, so you can feel good about being educated in speaking the Queen’s or the Prime Minister’s English.