Water everywhere!
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Marking
 |
Y4, 6, 8, 10 (07/2007) | |
| A river | Liquid | |
| The sea | Liquid |
moderate (Y4)
very easy (Years 6, 8, and 10)
|
| Snow | Solid |
moderate (Y4)
easy (Y6 and Y8)
very easy (Y10)
|
| Rain | Liquid |
moderate (Y4)
very easy (Y6, Y8, and Y10)
|
| Clouds | Liquid or Gas | for discussion go to Clouds and fog in Diagnostic and formative information |
| A glacier | Solid |
difficult (Y4)
moderate (Y6 and Y8)
very easy (Y10)
|
| Inside us | Liquid |
moderate (Y4)
easy (Y6, Y8, and Y10)
|
| Hail | Solid |
moderate (Y4)
easy (Y6)
very easy (Y8 and Y10)
|
| Fog | Liquid or Gas | for discussion go to Clouds and fog in Diagnostic and formative information |
| Inside a plant | Liquid |
difficult (Y4)
moderate (Y6 and Y8)
easy (Y10)
|
| In the air in the room where you are now | Gas |
difficult (Y4)
moderate (Y6)
very easy (Y8 and Y10)
|
Trial and reporting information
This resource was trialled with 655 students from Years 4-10, so the data collected provide a good indication of how students' ideas change over time. The trial numbers were Y4 (99 students), Y5 (15 students), Y6 (115 students), Y7 (51students), Y8 (128 students), Y9 (64 students) and Y10 (183 students)
NOTE 1: In this section the data from the separate years are considered. However, Year 5 was a particularly small group of just 15 students from 1 school who performed better on some questions than older students, probably indicating a school effect. Their results are not shown.NOTE 2: The results from the smaller samples of trial students will have a greater margin of error than the larger samples.
Why is "states of water" an important idea in science?
Knowing that water exists in three different states within the normal range of temperatures on Earth is fundamental to understanding the importance of water to life on our planet. It is also a precursor for understanding the processes of changes of state such as freezing, melting, evaporation, and condensation. We need to know about both the states that water exists in, and the processes that lead to changes from one state to another, to understand Earth's systems, such as the water cycle. Knowing about water helps us to make decisions about important environmental issues such as water usage and climate change.
Diagnostic and formative information
General trends and areas of difficulty
As the Year groups progress, the students increasingly gave the correct responses of the state of the water for all the locations. The first graph shows to what extent the different year groups correctly identified the state of water for each location except clouds and fog (These are shown in the second graph and discussed separately.)
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Student responses - identifying the correct states of water
locations of water |
The graph shows that:
- Students had more difficulty identifying the state of the water in contexts they may not have been familiar with (e.g., glacier); or
- They could not see (e.g., inside plants, inside us); and
- The exception to this is air. While for Year 4 trial students this was very challenging, by Year 10 almost all students knew that water in the air is a gas.
Clouds and fog
Clouds are a mixture of water vapour and liquid water, and sometimes ice crystals. In New Zealand, according to Erick Brenstrum, a New Zealand weather forecaster, most raindrops begin their lives as snowflakes. The proportions of water in the different states are dependant on environmental conditions, and result in the formation of different types of clouds. Once water vapour starts changing to liquid or solid water it becomes visible. A "don't know" answer, therefore, could possibly have been the most thoughtful response.Fog is cloud at ground level, and is also a mixture of water vapour and liquid water. Fog occurs as air cools, causing the water vapour to condense. Fog is denser than mist so contains more water droplets.
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Student responses: State of water in clouds
Year groups |
NOTE: There is no line linking the Y4 responses to the others because we did not include Y5 data.
- most students identified that the water exists predominately as a gas in clouds (similar results were obtained regarding fog, even though many students must have experienced the dampness of fog).
- water in a cloud is dynamic and undergoes constant change of state. In other words, a cloud is a system within which the processes of evaporation, condensation, freezing, and melting are going on. A diagram of a cloud system (in Other resources) illustrates this.
Suspending judgement
Although there was no one correct answer for cloud and fog, few students used the "don't know" option. In fact they were less likely to circle DK (don't know) as they got older, even though it could be expected that they would be more likely to be aware that there is a mixture of water in different states. This may be because:
- The question asked them to make a choice;
- Students are not keen to choose a "don't know" option when they know they are being assessed; or
- Students have not been ‘ingrained’ with an attitude that it is acceptable or safe to say, "I don’t know".
For formative purposes, the "don't know" responses are a useful starting point for class discussions, during which it is often easier to pinpoint the sources of confusion for students. Being unsure is often part of developing more complex understandings. It is important to find out why students are unsure, and also to reinforce that "don't know" is an acceptable response.
Science vocabulary
It is interesting that research, including from ARB trials, clearly shows that young children commonly think that clouds are containers for rain, and yet less than 20% of Year 4 students circled liquid. This possibly indicates that some students don't know some of the specialised science language used in this question, such as "state", "liquid", "solid", and "gas". If this is the case, this assessment item may not be valid for all students. Especially with younger students or those lacking the technical language, this task could be better used as the basis for a whole class discussion, with some emphasis placed on unpacking the language.
For more information, go to Language of science (Specialised language).
- Students who perform poorly on this question may benefit from checking that they know what "changes of state" means, and then exploring the characteristics of each state. Looking at pictures and identifying the state of water provides practice in this.
- Redo the activity as a group activity, so students have to justify their choices. Encourage the use of the DK option, as these examples provide productive starting points for class discussions and follow up research.
- Ask students to debate the question, "Is steam a liquid or a gas?" (Like clouds and fog, it is a mixture. We see steam because the water molecules are beginning to clump together as they lose energy forming tiny drops of liquid water.) You are likely to find that students become quite confused about at what point water vapour becomes liquid water. This is a positive sign that they are becoming aware of the complexity of the processes of changing states.
- Explore what happens to water within a cloud. Thinking about a cloud as a system will be challenging for many students. Use the diagram of a cloud system as a basis for discussion before investigating different sorts of clouds. Suggest which state of water is likely to be most prevalent in different clouds, giving reasons.
- What else could happen to the liquid water that makes up a cloud?
- If it doesn't fall as rain, what else could happen to the water in a cloud?
An English resource, Changes of state II, is about finding the features of a science text. The context is changes of state.
Ministry of Education (2004). Connected 2. Wellington: Learning Media. Refer also to the accompanying Teacher Notes.Two articles about weather include information about states of water within clouds.\ Thunder and lightning Hard ice, soft ice Ministry of Education (1999). Connected 2. Wellington: Learning Media. Refer also to the accompanying Teacher Notes.There are three articles about frost, mist, and fog: Strange white world Mist How to make your own mist and smog
Websites
http://www.niwascience.co.nz/edu/students/clouds
http://www.bom.gov.au/info/clouds/
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml
