A purpose of Science is to understand and explain the world around us. Our understanding of the world is often developed through experimentation.
In Science, students have to recount the procedures completed in their experiments and explain how and why something occurred.
Two common genres of writing in Science are procedural recounts and explanations. Explanations can be further divided into:
- sequential explanations
- causal explanations.
Sequential explanations are concerned with explaining the flow of a series of events according to the time they happen (Derewianka & Jones, 2016).
Causal explanations focus on explaining the cause and effect related to a particular phenomenon.
The strategies below will help teachers to support students’ literate skills to write procedural recounts, and to understand and develop sequential and causal explanations:
- Writing experimental methods
- Reading and writing sequential explanations
- Teaching Theme and Rheme
- Expressing scientific cause and effect.
Writing experimental methods
The experimental procedure, or method, is an example of a procedural recount. The method outlines the steps a scientist has performed in order to complete an investigation or experiment. Teaching how to write experimental methods appropriately supports development of Science Inquiry Skills (VCSIS113,
To help students plan experimental methods, teachers should emphasise the sequential nature of experiments. To do this, teachers can:
- encourage students to use numbered steps
- ask students to draw a flow chart to show the sequence of events in an experiment
- include directions and actions in present tense.
When writing the method as part of an investigation report (after the experiment has been performed), the method should be written in:
- numbered steps
- the past tense
- passive voice.
The passive voice is created when the subject of the sentence has something done to it. An example of the passive voice is “The solution was poured”; the solution (the subject of the sentence) had “pouring” done to it.
Below is one method to teach students to construct the passive voice when writing their experimental methods (Custance, Dare & Polias, 2011):
- Student write the actions they performed as part of the method, ensuring verb is in past tense.
|I||dropped||the ball||from a height of 1 m.|
|“the doer” (subject) ||“the action” (verb, past tense) ||“the done-to" (object) ||prepositional phrase |
- Students swap the subject and object around, changing the verb to the passive voice so that the sentence makes grammatical and semantic sense.
|The ball||was dropped||by me||from a height of 1 m.|
|“the done-to” (subject) ||“the action" (verb, past tense) ||"the doer" (object) ||prepositional phrase |
- Students delete reference to themselves or their classmates (the object).
|The ball||was dropped||from a height of 1 m.|
|“the done-to” (subject) ||“the action" (verb, past tense) ||prepositional phrase |
(adapted from Polias, 2016, p. 149)
Reading and writing sequential explanations
There are two stages of sequential explanations:
- the phenomenon stage
- the explanation sequence stage.
The phenoenon stage identifies the phenomenon, while the explanation sequence stage contains written text and/or images to explain each phase of the sequence.
Explicit teaching (HITS Strategy 3) can be used to provide students with an understanding of the common features of sequential explanations. Knowing these common features should help students to both read and write sequential explanations in Science.
The features of sequential explanations that should be explicitly taught to students include:
- emphasising sequential explanations in diagrammatic form are often read either:
- left to right, which matches the movement of written text in English
- identifying the function of different text enhancements (for example - bold, italics)
- identifying any temporal elements, including conjunctions (when, as), verbs (begins, ends) or time periods (100 seconds, 2 days)
- highlighting how new information that is presented in one phase usually provides the beginning for the next phase. (Polias, 2016, pp. 36–37)
Teaching theme and rheme
When writing, the Theme and Rheme structure helps with the flow of information (Christie & Derewianka, 2008). In simple terms, the Theme is the beginning of the clause or sentence, while the Rheme is the rest of the clause or sentence. The Theme establishes the known information, while the Rheme introduces new information. To assist with the flow of information in an explanation, the Rheme of a preceding sentence will often form the Theme of the next sentence.
In the example below from a Year 9 or 10 class (VCSSU118), the Themes are highlighted purple and the Rhemes are highlighted green. The Rheme of the first sentence, “involuntary response”, is changed to “The action is involuntary” and becomes the theme of the second sentence.
A reflex action
is an involuntary response to a stimulus. The action is involuntary because the neural pathway for the action does not involve the brain. The neural pathway of a reflex action is called a reflex arc.
Sequential explanations of a process often follow a pattern where the Theme is the name (subject) of a stage in the process, while the Rheme is the explanation or definition of that stage.
When writing, teachers can use a table to help model the Theme and Rheme structure to support students to develop sequential explanations. The example below is designed to help Year 7 and 8 students write a sequential explanation for the treatment of sewage water (VCSSU095,
- Construct a Theme and Rheme table for the process.
- List the stages of the process in order in the Theme column.
|Flocculation||is when chemicals are added to cause fine particles to clump together to form a floc.|
|Sedimentation||is when large particles settle at the bottom of the water|
|Filtration||removes particles that remain in the water after sedimentation|
|Disinfection||removes pathogens from the water|
|Fluorination||adds fluorine to the drinking water|
- Students read text, watch a video, or use prior knowledge to complete the Rheme section.
- Students write a beginning sentence using the following structure (or a variation):
Students complete the sequential explanation by adding in the information from the table.
- The [name process] consists of [number of stages] stages: [list stages].
The treatment of sewage water consists involves five stages: flocculation, sedimentation, filtration, disinfection and fluorination. Flocculation is the when chemicals are added to cause fine particles to clump together to form a floc. Sedimentation is when particles settle at the bottom of the water. Filtration removes particles that remain in the water after sedimentation. Disinfection removes pathogens from the water. Fluorination adds fluorine to the drinking water.
- Students can then revise and edit their consequential explanation to improve clarity and flow. This may involve adding:
- temporal connectives (e.g. then, The next stage)
- temporal processes (e.g. … is followed by …).
The treatment of sewage water consists involves five stages: flocculation, sedimentation, filtration, disinfection and fluorination. The first stage is flocculation. During flocculation, chemicals are added to cause fine particles to clump together to form a floc. Sedimentation is the next stage, and particles settle at the bottom of the water. Filtration follows sedimentation to remove any particles that remain in the water after sedimentation. Disinfection comes next and removes pathogens from the water. Fluorination is the final stage. During this stage, fluorine is added to the drinking water.
When reading, students can be encouraged to highlight the Theme and number the stages of the Theme.
Expressing scientific cause and effect
Being able to express cause and effect is an aspect of the Science Inquiry Skills (VCSIS111,
To develop students’ ability to express causal relationships, teachers can introduce students to specific language features.
The table below outlines some language resources teachers can use with their students when writing causal relationships. Resources for expressing causal relationships (Polias 2016, p. 132)
|Causal conjunctions or connectives|
To join clauses to make sentences:
- because, so, since, as, so.
To join sentences and paragraphs:
- Therefore, Thus, As a result, As a consequence, Hence.
|Causal processes||results in, leads to, causes, produces|
|Causal prepositions||because of, due to, as a result of|
|Causal nominals||cause, reason, factor, effect, consequence, outcome, product, result |
Teachers can also use modelling to teach students how to write succinct and flowing causal explanations when writing the discussion section of a practical (prac) report. The following strategy has been adapted from Polias (2016) and can be considered as a worked example (HITS Strategy 4).
- Students conduct a practical investigation and collect data.
- The teacher writes down an observation from the experiment in the past tense.
- The teacher and students jointly construct a first draft of an explanation for the observation. For example, the teacher could:
The teacher and students revise the causal explanation, restructuring sentences and removing repetition to improve clarity of expression. As the students’ ability to edit their own writing improves, the teacher takes less of an active role.
- ask the students five whys (or similar questions), writing their responses on the board
- write “because” after the written observation, talking-out their scientific reasoning.
An example of a teacher using the “five whys” to elicit a student explanation of a chemical reaction in a Year 9 or 10 class is below (VCSSU123,
VCSSU125). The teacher writes the students’ answers on the board, and then leads a discussion to edit and refine a written conclusion for the experiment.
Observation: Bubbles formed when magnesium was placed in hydrochloric acid
Students: The magnesium reacted with the hydrochloric acid.
Students: Metals react with acids.
Teacher: What is produced?
Students: Bubbles are produced.
Teacher: What are the bubbles?
Teacher: What gas?
The explanation is predominantly in the past tense because the students are relating their observations of what has occurred.
First draft of causal explanation
Bubbles formed when magnesium was placed in hydrochloric acid. The magnesium reacted with the hydrochloric acid. Metals react with acids. Bubbles are produced. Gas. Hydrogen.
Second draft of causal explanation
Bubbles of hydrogen gas formed when magnesium was placed in hydrochloric acid. The magnesium reacted with the hydrochloric acid to produce hydrogen gas. Metals react with acids.
Third draft of causal explanation
Metals react with acids. When the magnesium strip was placed in the hydrochloric acid, hydrogen gas was produced in the form of bubbles.
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Custance, B., Dare, B., & Polias, J. (2011). How language works: Success in literacy learning. Adelaide: Department of Education and Child Development.
Derewianka, B., & Jones, P. (2016). Teaching language in context. New York: Oxford University Press.
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