A transfer moves matter or energy from one location to another without changing its form, while a transformation changes the state, chemical nature, or energy form of matter or energy. This distinction is part of IB ESS Subtopic 1.2, Systems, for both SL and HL.
How the Distinction Works
A system consists of storages connected by flows. In a systems diagram, storages are normally represented by rectangular boxes and flows by arrows showing their direction. A flow may be either a transfer or a transformation.
| Process | What happens? | ESS examples |
|---|---|---|
| Transfer | Matter or energy changes location but retains the same form. | Water moving by surface run-off; soil being moved by erosion; organic matter passing from prey to predator through feeding |
| Transformation | Matter or energy changes state, chemical nature, or energy form. | Liquid water becoming water vapour through evaporation; organic matter decomposing into inorganic nutrients; light energy becoming chemical energy through photosynthesis |
Consider the hydrological cycle. Advection transfers water vapour horizontally through the atmosphere because the water remains water vapour. Condensation transforms water vapour into liquid water because its physical state changes.
In a soil system, leaching transfers dissolved minerals downward through the soil profile. By contrast, decomposition transforms dead organic matter into simpler substances, releasing mineral nutrients that plants can absorb.
The common misconception is that every arrow between storages represents only movement. In fact, arrows represent flows, and some flows involve a change in form rather than simply a change in location. A process can also involve both: combustion transforms stored chemical energy and transfers heat to the surroundings.