C4.2.3—Chemical energy flow
Chemical energy flow explains how energy flow, matter cycling, trophic transfer or carbon movement is represented, measured or limited within ecosystems.
- Syllabus
- First assessment 2025
- Objective
- C4.2.3
- Level
- HL
Exam analysis
Chance of appearing8%of analysed past papers
Latest appearanceNovember 2024
Most common paperPaper2
Typical marks1–3
Common command terms
- Outline
- Explain
- Describe
- Identify
- Distinguish
Scoring notes
- Common mistake
- Skipping the conversion of light energy into chemical energy by producers.
Recent exam appearances
November 2024Paper1 ["HL"] · TZ015[ 1 ]C4.2.3—Chemical energy flow
May 2024Paper3 ["HL"] · TZ117(a)[ 3 ]C4.2.3—Chemical energy flow
November 2023Paper2 ["HL"] · TZ27(a)[ 7 ]C4.2.3—Chemical energy flow
May 2022Paper1 ["HL"] · TZ216[ 1 ]C4.2.3—Chemical energy flow
May 2021Paper2 ["HL"] · TZ24(c)[ 3 ]C4.2.3—Chemical energy flow
Practice this objective
Coverage 2016–2024 · Updated 16 Jul 2026
Concept essentials
- Chemical energy flow must be linked to the correct source, store, transfer or loss process.
- The evidence for chemical energy flow depends on distinguishing energy flow from matter cycling.
- Chemical energy flow is clearer when arrows, units and trophic positions match the biological process.
- Data or diagrams for chemical energy flow need interpretation as ecosystem transfer evidence.