Look up a few obvious - and less obvious - science words and fill in five minutes at the end of a lesson. Use a textbook glossary as a starting point. Try the symbol Pb for lead, derived from the Latin "plumbum"; discuss plumbers and phrases like "plumbing the depth". Or try "exo" as in exothermic; exodermis; exit; exoskeleton, externa - all deriving from the Greek meaning "outside". Hydrophilic or hydrophobic reveal a philia or a phobia from the Greek for lovehate (as in arachnophobia, claustrophobia and - maybe - schoolphobia). There are some surprises: "Eutrophication", describing the algal bloom in rivers and streams due to fertilisers, means "overeating".