Overview
Science subjects are among the most popular Leaving Cert choices. There are three main science subjects: Biology, Chemistry and Physics. Agricultural Science is also available but covered separately. Each subject is examined at Higher and Ordinary Level, with a mix of written exams and practical coursework components.
Leaving Cert Biology
Biology is consistently the most popular Leaving Cert subject, taken by over 30,000 students annually.
Course Content
- Unit 1: The Study of Life: scientific method, characteristics of life, ecology
- Unit 2: The Cell: cell structure, cell division (mitosis, meiosis), DNA, RNA, protein synthesis, genetics, enzymes
- Unit 3: The Organism: photosynthesis, respiration, human systems (digestive, circulatory, nervous, immune, excretory), plant biology
Exam Structure
- Two written papers (or one long paper depending on year): 3 hours each at HL
- Mandatory practical activities: 22 specified experiments (10 — 12 assessed in the exam)
- Questions test recall of facts, application of biological concepts and experimental design
Tips for Biology
- Learn the definitions precisely: examiners expect exact terminology
- Draw and label diagrams: practice cell diagrams, heart, kidney, leaf cross-section, DNA structure
- Know the mandatory experiments inside out: aim, method, result, conclusion
- Biology is content-heavy: start revision early and use flashcards
Leaving Cert Chemistry
Chemistry is required or recommended for medicine, pharmacy, veterinary science, dentistry and many science courses.
Course Content
- Unit 1: Atomic structure, periodic table, bonding, mole concept, stoichiometry
- Unit 2: Rates of reaction, equilibrium, acids and bases, oxidation-reduction, electrochemistry
- Unit 3: Organic chemistry: hydrocarbons, alcohols, carboxylic acids, organic reactions, polymers
- Unit 4: Option topics: atmospheric chemistry, materials, industrial chemistry (varies by year)
Exam Structure
- Two papers: Paper 1 (short questions + longer Qs on Units 1 & 2), Paper 2 (Units 3 & 4)
- 28 mandatory experiments: questions appear regularly on the exam
- Calculations are a significant part: balancing equations, mole calculations, pH, E° values
Tips for Chemistry
- Practice calculations daily: the mole concept is central to the entire course
- Learn the trends in the periodic table (ionisation energy, electronegativity, atomic radius)
- Memorise organic reactions: functional groups, reaction types and reagents
- Know the colour changes and equations for every mandatory experiment
Leaving Cert Physics
Physics is essential for most engineering courses and is highly valued for computer science and architecture.
Course Content
- Unit 1: Optics: reflection, refraction, lenses, wave nature of light
- Unit 2: Mechanics: vectors, forces, Newton's laws, energy, momentum, circular motion, gravity
- Unit 3: Electricity & Magnetism: circuits, resistance, capacitance, electromagnetism, induction
- Unit 4: Modern Physics: quantum theory, radioactivity, nuclear physics, particle physics
- Unit 5: Heat & Thermodynamics
Exam Structure
- Two papers: Paper 1 (Mechanics, Heat, Optics), Paper 2 (Electricity, Modern Physics, Options)
- Mandatory experiments: 22 practical activities, tested in the written exam
- Mathematical problem solving is central: students must be comfortable with algebra
Tips for Physics
- Learn the equations and understand when to apply each one: formula sheet is provided but knowing which to use is key
- Practice derivations: many exam questions ask you to derive a formula (e.g., F=ma from Newton's laws)
- Draw diagrams for every problem: labelled free-body diagrams are essential
- Do past exam questions by topic: Physics questions follow very predictable patterns
Which Science Subject Should You Choose?
- Biology: Good if you have strong memory skills. Great for medicine, nursing, physiotherapy, genetics, environmental science
- Chemistry: Good if you can handle calculations and like logical systems. Essential for medicine, pharmacy, dentistry, chemical engineering
- Physics: Good if you are strong at maths and problem solving. Essential for engineering, architecture, physics, computer science
- Two sciences: Many ambitious students take Biology + Chemistry or Chemistry + Physics to maximise course options
Science Subjects in 2026: The Big Picture
Biology, Chemistry and Physics remain the most popular science choices in the Leaving Cert, and 2026 was another record year for the exam cohort overall — 71,698 Leaving Cert candidates, up 9% on 2025. All three sciences are examined by two written papers each at Higher and Ordinary Level, with practical coursework marks (20% in Chemistry and Physics) already banked before the June exams. The SEC confirmed the post-marking adjustment continues in 2026, with results expected just below 2020 levels.
Demand for science courses at third level is booming — UCD's Sport, Health and Exercise Science and Radiography saw first-preference applications jump by over 40% in the 2025 CAO cycle, and Radiography's entry points climbed accordingly. A strong science subject is increasingly the key that unlocks the most competitive health, engineering and technology courses.
New for Science Students: Climate Action and Sustainable Development
From 2025, schools began offering a brand-new Leaving Cert subject: Climate Action and Sustainable Development, introduced on a phased basis alongside Drama, Film and Theatre Studies. The subject blends science, geography, economics and social studies, and covers climate science, sustainability policy, biodiversity and the energy transition — with assessment designed around research and case studies rather than pure memorisation.
For students who love science but want something beyond the traditional three, it is worth asking your school whether it is available. Meanwhile, the traditional sciences are also on the reform schedule — Physics and Chemistry are due for redevelopment in Tranche 3 (2027), so today's Junior Cycle students will meet the new specifications when they reach senior cycle.