Investigating the water cycle

Investigating the water cycle

Pencil and paperOnline interactive
Overview
Using this Resource
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
This task is about investigating the water cycle.
Sam was investigating the water cycle.  He set up an experiment.
When the water in the jug was boiling he got a large metal spoon that had been in the freezer for an hour and put it in the steam.
 
diagram of experiment investigating the water cycle

Question

a)  What are the bubbles in the jug?

    • The bubbles are air.

    • The bubbles are heat.

    • The bubbles are oxygen or hydrogen.

    • The bubbles are water vapour.

Question

b)  i)  Which part of the water cycle does Water droplets from spoon show? 

    • The sun

    • Rain

    • Oceans

    • Clouds

Question

b)  ii)  Which part of the water cycle does Heating element in the jug show?

    • The sun

    • Rain

    • Oceans

    • Clouds

Question

b) iii) Which part of the water cycle does Water in the jug show?

    • The sun

    • Rain

    • Oceans

    • Clouds

Question 2Change answer

c)  In some ways Sam's experiment is like the real water cycle and in other ways it is different.
     Think carefully about each statement in the chart below and chooose True, False or Don't know.
  Experiment Real water cycle
The water evaporates. TrueFalseDon't know TrueFalseDon't know
The water must be hot. TrueFalseDon't know TrueFalseDon't know
Rain falls in the same place where the water evaporated. TrueFalseDon't know TrueFalseDon't know
Condensation needs a cold place. TrueFalseDon't know TrueFalseDon't know
We can't always see water. TrueFalseDon't know TrueFalseDon't know
Task administration: 
This task can be completed with pencil and paper or online.
Copyright: 
Graphics: copyright NZCER.
Levels:
2, 3, 4, 5
Curriculum info: 
Science, Communicating in science, Planet Earth
Key Competencies: 
Thinking, Using language, symbols, and texts
Keywords: 
interacting systems, water cycle, evaporation, condensation, models, key competencies, self assessment, matching
Description of task: 
Task: Match the parts of a water cycle to the parts represented in a model of the water cycle and compare how they are the same and different. Assessment focus: interpreting a model.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask.
 
Capability: Interpret representations
Scientists represent their ideas in a variety of ways, including models, graphs, charts, diagrams and written texts. This resource provides opportunities to discuss what a model shows, and how it is the same and different from the real thing.
 
Science capabilities: 
Interpret representations
Answers/responses: 
  Y4, 6, 8, 10 (07/2007)
a) The bubbles are water vapour. difficult or very difficult
(all years)
b) Water droplets from spoon = rain moderate (Y4)
easy (Y6)
very easy (Y8 and Y10)
Heating element in jug = sun moderate (Y4)
easy (Y6)
very easy (Y8 and Y10)
Water in jug = oceans difficult (Y4)
moderate (Y6)
very easy (Y8 and Y10)
c)  
 
The water evaporates.		 Experiment
 
T		 Real water cycle
  
T		 difficult (Y4)
moderate (Y6)
easy (Y8 and Y10)
The water must be hot. T F very difficult (Y4)
difficult (Y6)
moderate (Y8 and Y10)
Rain falls in the same place where the water evaporated. T F very difficult (Y4)
difficult (Y6)
moderate (Y8 and Y10)
Condensation needs a cold place. T T very difficult (Y4)
difficult (Y6 and Y8)
moderate (Y10)
We can't always see water. T T difficult (Y4 and Y6)
moderate (Y8 and Y10)

Results are based on a trial set of 655 students from Years 4-10, in July 2007. The difficulty levels are based on student data from Year 4 (99 students), Year 6 (115 students), Year 8 (128 students), and Year 10 (183 students).

Teaching and learning: 
Why is the water cycle 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: 

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 one 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.  

  Common response Likely misconception
a) The bubbles are air Equate gas with air, i.e., if we can't see it, it is air. (NOTE: When the water first starts warming up, air that is dissolved in the water can be seen as air bubbles.)
a) The bubbles are heat Think that heat is a physical substance, rather than a transfer of energy.
a) The bubbles are oxygen or hydrogen Think that the water molecules split into hydrogen and oxygen to form a gas.
c) The water must be hot (water cycle) Consider boiling to be evaporation, or that evaporation only occurs when water boils. The scientific definition for evaporation is changing state from a liquid to a gas at below boiling point. For younger students it is more important that they know that boiling is not the only means by which water changes to a gas.
Next steps: 

What are the bubbles in the jug?
This is a classic question asked by science education researchers. It was a very difficult question for our trial students. However, it is a useful marker question for assessing how well students understand evaporation, especially the "invisibility" of water as a gas, and for identifying what misconceptions they hold. If your students have a fairly strong understanding of evaporation, sharing, debating, and justifying their ideas may help to highlight and clarify areas of difficulty.

  • Ask students to write down why they chose the answer they did and then any questions they have.
  • Use the doughnut strategy to share both bits with three partners
  • Ask students to write down what they think now and why.

Follow up with a class discussion:

  • Display each choice.
  • What ideas do we have?
  • Do we have evidence to support our theories?
  • Is there any evidence that conflicts with our ideas?

 

Exploring models potentially incorporates aspects of the Nature of science strand, and contributes to the development of the key competencies Using language, symbols, and texts and Thinking, as well as being an effective strategy for teaching science concepts. Models are used by scientists to carry out investigations, to communicate their ideas, and as a thinking tool.

Demonstrate the model to the students, so they can observe what is happening. Use the questions from the task as discussion questions.

  • Set up a different model of the water cycle e.g., see page 13 of Building Science Concepts Book 31, Water and weather (go to Other resources).
  • Discuss or design a similar matching activity of what each part of the model represents of the real water cycle. Critique where the model is different from a real water cycle.

            What elements of a water cycle does the model focus on?
            Which elements are missing?

  • Compare with a water cycle diagram.

            What does the model show that the diagram doesn't?
            What does the diagram show that the model doesn't?

  • Compare the boiling water model in the resource with a non-boiling model, e.g., see page 13 of Building Science Concepts Book 31, Water and weather (go to Other resources).

Evaporation only occurs when the water is hot

Set up fair tests to investigate different scenarios suggested by students as possible factors in evaporation, e.g., hot water, cold water, in the sun, in a cool place, in a windy place. (Paper towels can be quite quick, but students may need assistance in keeping the amount of water absorbed by the paper towel the same.) Chart or graph results and compare. Groups can then discuss what they think the results show, and report back to the class.

Changes of state, is about finding the features of a science text. The context is changes of state.
  • Ministry of Education (2001) Where's the water? Building Science Concepts Book 15. Wellington: Learning Media.
  • Ministry of Education (2003) Water and weather. Building Science Concepts Book 31. Wellington: Learning Media.  Two activities that model clouds and rain are included on pages 12 and 13.
  • Ministry of Education (2002). Connected 2. Wellington: Learning Media. Refer also to the accompanying Teacher Notes. There are two articles about the water cycle: An interview with a glass of water and The water cycle
  • Ministry of Education (2000). Connected 1. Wellington: Learning Media. Refer also to the accompanying Teacher Notes. Making puddles is about a class investigating the evaporation of puddles. 
  • Ministry of Education (1999). Connected 2. Wellington: Learning Media. Refer also to the accompanying Teacher Notes. The  article How to make your own mist and smog features another model: 

For our summary of research related to teaching about the water cycle, go to Salient points from the literature about understanding the water cycle. Joyce, C. (2007).

Some musings about the links between formative assessment and the development of key competencies. set: Research information for teachers, 2, 50-52. This short article discusses interpreting models.