Harry Potter: Chemical Detective – Part 1
"Alright, today our lesson will also include some math. Don't get too excited," said Mr. Johnson.
"What's math?" Neville asked.
Mr. Johnson shook his head. "Anyway, on with the lesson. We'll be dealing with chemical equations. They cannot break the Law of Conservation of Mass. Who knows what that is?"
"It's the law that says matter cannot be created nor destroyed," Hermione said.
"Excellent. A chemical equation represents what happens in a chemical reaction. It looks like this." Mr. Johnson proceeded to write a chemical equation on the board. "Now, who can tell me what this is?" He pointed to one of the numbers he had written.
"Erm…the number two?" Harry guessed.
"No. It's the subscript, and it tells us how much of each atom is in a compound. And what are these letters here?"
"Hurting my eyes?" Ron said.
"Clever, Weasley, but no. They are the element's symbol, and they tell us what elements are in the compound. Like this one here. H2O. Who can tell me what it is?"
"Water!" Seamus said.
"Correct, Mr. Finnigan. And what two elements are in water?"
"Hydrogen and oxygen," Hermione said.
"Correct, Ms. Granger. And as you can see, the same elements on the left side of the equation are on the right side, just in a different order. Matter cannot be created or destroyed in a chemical change. Understand?"
"Sir, what's that big number in front?" Harry asked.
"Ah, the coefficient! It's another thing that tells us how many atoms are in a compound, but it pertains to all elements in the compound. Now, a bit about chemical changes. They cannot be reversed, and they change the identity of the substance. Who can give me an example of a chemical change?"
"If Ron got a perfect score on a test," Harry said.
"No, sorry, Mr. Potter, that is incorrect."
"Burning, baking, or rotting," Hermione said.
"Yes, excellent! Now, what is a precipitate?"
"A solid that is formed as a result of a chemical reaction, usually from liquid reactants."
"Yes!" And then, to Harry's delight, the bell rung. But Mr. Johnson stopped them before they could leave. "Excellent job today. Your homework is to write me an essay about the kinds of chemical reactions. Class dismissed."
As they were leaving, Ron asked Harry, "D'you know what the word chemical means?"