"Is it stopped?"
Toma shook the flask.
"It's not stopped," Rei answered immediately. "It's in equilibrium."
"Equilibrium? But there's no change."
"No macroscopic change. Microscopically it's moving intensely."
Kana showed interest. "What do you mean?"
Milia explained. "Reversible reaction. A becomes B, and B returns to A. Both happen simultaneously."
"Simultaneously?"
"A state where forward and reverse reaction rates are equal. That's equilibrium."
Rei drew a diagram. "Apparently static, but at molecular level conversion continues constantly."
Toma was surprised. "It's dynamic?"
"Dynamic equilibrium. Not static."
Kana wrote in her notebook. "Reaction continues but concentration is constant?"
"Exactly," Milia nodded. "Production and consumption rates are balanced."
Rei continued. "Equilibrium constant K. This determines the system's properties."
"K = [B]/[A]?" Toma asked.
"For simple reactions, yes. If K is large, it favors the product side."
Kana asked. "Does K change?"
"Changes with temperature. But not with catalysts."
"Catalysts?"
"Only change reaction rate. Don't change equilibrium position," Milia answered.
Toma was confused. "Then what are catalysts for?"
"Shortening time to reach equilibrium."
Rei added. "They speed up both forward and reverse reactions by the same factor. So equilibrium doesn't change."
Kana understood. "Same destination. Just arrives faster?"
"Good metaphor."
Milia added reagent to the flask. "What if I add this?"
Toma watched. The color changed.
"Concentration changed," Rei said. "Equilibrium shifts."
"Shifts?"
"Le Chatelier's principle. The system moves to counteract external changes."
Kana was confused. "Counteract?"
"If you add reactant, equilibrium shifts to consume it, toward products."
Toma laughed. "Nature dislikes change?"
"It prefers energetically stable states," Milia explained.
Rei gave another example. "If you increase pressure?"
"For gas reactions, it shifts toward fewer molecules," Kana answered.
"Correct. Direction that reduces volume."
Milia showed a thermometer. "If you raise temperature?"
"For endothermic reactions, shifts toward heat absorption direction," Toma said.
"Meaning product side?"
"Exactly. Opposite for exothermic reactions."
Kana murmured. "The reaction vessel is like a small universe?"
"Interesting expression," Rei acknowledged. "In a closed system, everything interacts."
Milia continued. "Same in living organisms. Countless equilibria exist simultaneously."
"Simultaneously?"
"Metabolic pathways. When one equilibrium moves, others are affected."
Toma got excited. "Chain reaction?"
"Not chain, but network. Everything's connected."
Rei emphasized. "So life isn't in equilibrium. It's in steady state."
"Different?" Kana asked.
"Equilibrium is closed system. Steady state is open system. Energy and matter flow in and out."
Milia added. "Being alive means being away from equilibrium."
"Equilibrium is death?"
"In a sense."
Toma stared at the flask. "When this microcosm reaches equilibrium, what happens?"
"Nothing changes. Stays that way forever."
"Boring?"
Rei laughed. "But that's what stability means."
Kana said quietly. "Life is beautiful because it's unstable."
"Philosophical," Milia smiled.
"But might be truth," Rei admitted.
The four gazed at the reaction vessel. Inside, countless molecules kept dancing.