Topic C3: Chemical reactions

Topic C3: Chemical reactions is a core component of the OCR GCSE Chemistry specification, covering the fundamental principles that govern how substances interact and transform. This topic explores the different types of chemical reactions, including oxidation, reduction, displacement, and neutralisation, as well as the energy changes involved. Students will learn to write and balance chemical equations, predict reaction products, and understand the reactivity series of metals. Mastery of this topic is essential for explaining real-world processes such as rusting, combustion, and acid-base reactions in industry and everyday life.

Chemical reactions are at the heart of chemistry, linking atomic structure to the behaviour of materials. In this topic, you will investigate how atoms rearrange during reactions, why some reactions release energy (exothermic) while others absorb it (endothermic), and how to represent these changes using word equations, symbol equations, and ionic equations. You will also explore the concept of conservation of mass and how to calculate reacting masses using relative formula masses. Understanding these ideas provides a foundation for more advanced topics like electrolysis, rates of reaction, and chemical equilibria.

This topic is assessed across both Paper 1 and Paper 2 of the OCR GCSE Chemistry exam, often through questions that require balancing equations, identifying reaction types, and interpreting energy level diagrams. Practical skills are also tested, such as carrying out neutralisation titrations and investigating displacement reactions. By the end of this topic, you should be able to apply your knowledge to unfamiliar contexts, explain observations using scientific reasoning, and perform calculations with confidence.