He checks the schedule, next class up... "Right, Chemistry! Do you think that Mrs. White will tell us what is in those jars with the frogs today?" Last class, Art had been roundly scolded for sticking his nose into a beaker to smell the contents. It was just a harmless salt solution, but it's the principle of the matter, apparently.
Gwen, of course, knows MUCH better. A substance of that granularity, color and weight could have been any number of poisons, several of which she can think of the compositions thereof...