"What?!"

A sigh. "Alchemy is only offered to sixth and seventh year students...at my discretion."

"But we start with electives in third year!"

"Not with Alchemy."

"Why not?!"

Snape gave her an exasperated look. "Tell me, what is the difference between an acid and a base?"

"...which definition?"

"Exac-" a pause. "Explain yourself."

"Liebig? Arrhenius? Lewis? Bronsted-Lowry? You can't have meant Lavoisier?"

"...you've studied Chemistry?"

"A bit."

"...very well." He drawled, intrigued, "Potions, Chemistry, and Transformative Charms, should you pass such a test I may consider teaching you early."

A gulp. "Did you say charms?!"

"Indeed."