6. Sequential explanations

A Sequential Explanation describes how a process unfolds over time.
This genre is common in school science texts, especially when explaining natural phenomena or scientific processes (e.g., how evaporation occurs, how a plant grows, how a chemical reaction happens).

6.1. Example

How Ice Changes from Solid to Liquid

Melting is a physical change in which a solid becomes a liquid. This explanation describes the sequence of events that occur when ice melts.

First, heat energy from the surroundings is absorbed by the ice. This increases the movement of particles in the solid. Next, as more heat is absorbed, the water molecules vibrate more quickly. They start to move out of their fixed positions in the solid structure. Then, the strong bonds holding the ice molecules in a rigid lattice weaken. The structure begins to collapse as the particles loosen. Finally, once the temperature reaches 0°C, the solid ice becomes liquid water. The molecules can now move freely, forming a liquid.

6.2. Stages and Phases in Systemic Functional Linguistics (SFL)

Stages

Stages are the major, compulsory sections of a genre.
They function as the large building blocks of the text.
Characteristics:

  • Each stage serves a distinct purpose.

  • The genre will not work properly if a compulsory stage is missing.

  • Stages structure the whole text.

Examples of stages in school science genres:

  • Sequential Explanation: Title → General Statement → Explanation Sequence

  • Procedure: Goal → Materials → Steps

  • Information Report: General classification → Description

Phases

Phases are the smaller functional units within each stage.
They organise how meaning unfolds inside a stage.
Characteristics:

  • Phases are sub-moves that contribute to the purpose of the stage.

  • They help guide the reader step-by-step through the meaning.

Example: Phases within a Sequential Explanation

In the General Statement stage - Phenomenon Identification - Optional Definition or Classification

In the Explanation Sequence stage - Temporal Staging (e.g., “first”, “next”, “then”) - Description of Actions/Events - Cause and Effect - Final Outcome

6.3. Stages and Phases of a Sequential Explanation

A Sequential Explanation describes how a process unfolds over time.
It presents events in a linear, temporal sequence.

Stage 1: Title

Phase: Topic Label

  • Names the topic or process.

  • Usually a short noun group.

  • Example: “How Evaporation Occurs”

Stage 2: General Statement

Phase 1: Phenomenon Identification

  • Introduces the phenomenon being explained.

  • States what it is in general terms.

Phase 2: Classification or Definition (optional)

  • May define the type of process.

  • May explain why the process is important.

Stage 3: Explanation Sequence

This is the main stage of the text.
It explains the process step-by-step in time order.

Phase 1: Temporal Staging

  • Uses time connectors such as: “first”, “next”, “then”, “after that”, “finally”.

Phase 2: Description of Actions or Events

  • Describes what happens in each step.

  • Uses material processes (e.g. “heats”, “vibrates”, “breaks”, “forms”).

Phase 3: Cause and Effect

  • Shows how each step leads to the next.

  • Connectors include: “because”, “therefore”, “as a result”.

Phase 4: Final Outcome

  • Describes the end state of the process.

Optional Stage: Concluding Statement

Phase: Summary or Significance

  • May restate the outcome.

  • May explain the importance of the process.

6.4. How Ice Changes from Solid to Liquid

Title

How Ice Changes from Solid to Liquid

General Statement

Melting is a physical change in which a solid becomes a liquid.
This explanation describes the sequence of events that occur when ice melts.

Explanation Sequence

Step 1: Heat Is Applied

First, heat energy from the surroundings is absorbed by the ice. This increases the movement of particles in the solid.

Step 2: Particles Begin to Vibrate Faster

Next, as more heat is absorbed, the water molecules vibrate more quickly. They start to move out of their fixed positions in the solid structure.

Step 3: Structure Breaks Down

Then, the strong bonds holding the ice molecules in a rigid lattice weaken. The structure begins to collapse as the particles loosen.

Step 4: Solid Turns into Liquid

Finally, once the temperature reaches 0°C, the solid ice becomes liquid water. The molecules can now move freely, forming a liquid.