Disclaimer: I don't own Harry Potter or the pot mentioned in the story.
'blah' means thoughts
Harry, Ron, and Hermione walked into the Potions classroom and took their normal seats. It was then (as Hermione was taking out her books, parchment, ink well, and quill) that Harry noticed a peculiar blue jar sitting on Snape's desk. It was pretty unremarkable except for the label on the front of the front, which read Ashes of Problem Students.
He nudged Ron in the ribs and pointed at the jar. "Do you think it's actually filled with ashes?"
Before Ron could answer, Hermione jumped in. "Do you honestly think Professor Snape is that vile? I know he's not the nicest professor, but to store actual ashes, student or otherwise, in a classroom is vile."
Harry and Ron stared at her for a moment before Ron said, "Who wants to look inside?"
"Why don't you do it, Ronald? If you're so sure, prove it."
"I'm not looking! I heard ashes stink," Ron answered, his voice quivering.
"Will you look, Harry?"
"No. I don't want to get on Snape's-"
"Professor Snape," Hermione corrected.
"-bad side anymore than I already am," Harry finished.
Hermione huffed. "Fine. I'll look, if for no other reason than to get this pointless discussion over with."
The bushy-haired Gryffindor got up and marched up to the teacher's desk. She stood in front of the jar, pulled on the lid, and looked in.
Her eyes widened, and she quickly replaced the lid. As she made her way back to her seat, Harry and Ron noticed her face had gone as white as Nearly Headless Nick. She sat down and attempted to speak, but no sound came out of her mouth. Harry and Ron glanced at each other and then back at Hermione. What could have her so spooked?"
Hermione took a deep breath and said, "There were ashes in there."
From the shadows, Professor Snape watched the antics of the Gryffindor Trio. He knew his jar would pique someone's curiosity. 'Who knew a glamoured jar of floo powder would rattle the Know-It-All?'
Author's Note: I know floo powder isn't the same color as ashes hence the use of the word glamoured. I also hope this doesn't offend anyone with loved ones who were cremated. I do not know first hand whether ashes have a distinct odor or not, but figured Ron would be so blunt to assume it.