Reversible Reactions and Equilibrium
Explaining dynamic equilibrium in closed systems and predicting qualitative effects of changed conditions.
How to study for GCSE Combined Science
Build the three sciences as connected disciplines, practise mathematical and practical reasoning, then apply the common core to the exact tier and paper structure of your current specification.
Core concepts
Concept 1
A reversible reaction can proceed in both directions and may reach dynamic equilibrium in a closed system.
Exam cue: State the closed-system condition and distinguish equal rates from equal concentrations.
Concept 2
At equilibrium forward and reverse rates are equal, while reactions continue and concentrations remain constant.
Exam cue: Use the direction that opposes the imposed change, then consider industrial trade-offs.
Concept 3
Changing concentration, pressure or temperature can shift equilibrium; a catalyst changes rates but not equilibrium position.
Targeted study blocks
Tier coverage
Foundation core with Higher-tier extensions
Dynamic-equilibrium explanations and qualitative effects of concentration, pressure and temperature are key Higher-tier extensions.
Risk pitfalls and guardrails
Saying reactions stop at equilibrium.
Guardrail: Do not import separate-science content or another route's paper order; use the full physics equations sheet required for current specifications while checking the exact series materials and entered tier.
Claiming a catalyst increases equilibrium yield.
Guardrail: Do not import separate-science content or another route's paper order; use the full physics equations sheet required for current specifications while checking the exact series materials and entered tier.
Memory anchors
Reversible reaction
A reaction able to proceed in both forward and reverse directions.
Dynamic equilibrium
Equal forward and reverse rates in a closed system with constant macroscopic composition.
Equilibrium position
The relative proportions of reactants and products at equilibrium.
Closed equilibrium system
A system that does not exchange reacting matter with surroundings.
Industrial compromise
A condition choice balancing yield, rate, energy, safety and cost.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
In a closed system, products can react to recreate the original reactants when conditions change. How is this reaction classified?
Why is a closed system needed for a stable dynamic equilibrium?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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