"Because in chemistry," Aina smiled, "when you add the right catalyst, even a broken reaction can start again."

That afternoon, Aina found a crumpled piece of paper on her desk. It was a photocopy of the "Kimia Tingkatan 4 Jawapan" section from the reference book. Someone had circled the answers for the next chapter on Ikatan Kimia (Chemical Bonds). But there was no working. No explanation. Just the final numbers.

When the quiz papers came back a week later, Lia didn't get an A. She got a C+. But next to her answer, Cikgu Fatihah had drawn a small smiley face.

Aina knew the handwriting. It was Lia's. The next day, before the quiz, Aina walked to Lia’s desk. She placed the crumpled paper between them.

"No, you don't." Aina pulled out her own notebook. On a fresh page, she had handwritten something. It wasn't the jawapan . It was the jalan kerja —the full method for balancing the equations, step by step, with little cartoons of sodium and chlorine atoms hugging to form ionic bonds.