Catalysts lower activation energy to increase reaction rates

Steps:

• Define catalyst: substance that speeds up reaction without being consumed by lowering activation energy (Ea).
• Analyze energy effects: catalysts provide alternative pathway with lower Ea, increasing fraction of collisions with sufficient energy.
• Evaluate options: check if each aligns with lowering Ea, not changing ΔH or thermodynamics.
• Select correct: option matching increased energetic particles.

Why C is correct:

• Catalysts lower Ea per Arrhenius equation (rate = A e^{-Ea/RT}), so more particles exceed Ea threshold to react.

Why the others are wrong:

• A: Catalysts lower Ea, not reaction enthalpy (ΔH), which remains unchanged.
• B: They lower Ea to boost rate, not alter ΔH.
• D: Heterogeneous catalysts are in different phase (e.g., solid for gas reactants) from reactants.

Final answer: C