Context
We live on a planet whose surface is mostly covered by water. The water cycle, also known as the hydrological cycle, is essential for life on Earth. It represents the circulation and conservation of water on the planet. When we think of the water cycle, we should automatically associate the idea of changing the physical state of water, because it is through these changes that the water on the planet is renewed and distributed.
Water goes through three states: solid, liquid, and gas. In the solid state, we find water in the polar regions in the form of ice and snow. In the liquid state, water is found in oceans, seas, rivers, lakes and underground. And, in the gaseous state, water is present in the atmosphere in the form of vapor. These physical transformations of water are part of the dynamics of the water cycle.
The physical state of water is the result of a balance between the forces of cohesion, which tend to keep the molecules together, and the forces of agitation, which tend to move them away. When the temperature is low, the forces of cohesion are predominant and the water is in the solid state. As the temperature increases, the forces of agitation also increase, causing a break in the bonds between the water molecules and its passage to the liquid state. Finally, when the temperature is high enough, the water molecules are agitated in such a way that they are able to completely overcome the cohesive forces and pass into the gaseous state.
The water cycle is of paramount importance for life on Earth, as it influences the climate, the formation of landscapes, agriculture, the production of energy and, of course, the availability of water for human consumption.
Agriculture, for example, is heavily dependent on rainfall, which is a direct result of the condensation and precipitation process of the water cycle. Similarly, the generation of energy in hydroelectric plants is only possible due to the movement of water in rivers, which is also part of this cycle.
It is recommended that the following resources be used to deepen studies:
- Water Cycle - Brasil Escola, Uol.
- Understand the Water Cycle - Canal Ciência, Brazilian Institute of Information in Science and Technology.
- Water Cycle and Physical States - Infoescola.
Hands-on Activity
Title of the Activity: Performing the Water Cycle
Objective of the Project
The objective of the project is to allow students to observe and understand in practice how the water cycle occurs, highlighting its stages and importance. In addition, the project aims to stimulate collaboration, effective communication, time management and problem solving.
Detailed Description of the Project
Students will be divided into groups of 3 to 5 members. Each group will be responsible for reproducing the water cycle in a practical and visual way, using materials that can be easily found. In addition to this hands-on activity, it is essential that the group write a report explaining the experiment.
Required Materials
- A transparent plastic or glass jar with a lid (an empty ice cream jar, for example);
- Water;
- Soil or sand;
- Small plants (optional);
- Stone or clay (optional);
- Sun.
Detailed Step-by-Step
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Put a reasonable amount of soil or sand on the bottom of the jar.
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If you wish, place small plants in the jar.
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Add water until the soil or sand is completely covered.
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Close the jar tightly with the lid.
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Place the jar in sunlight and observe for a few hours or days.
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Students should take frequent notes on what they observe.
In this mini ecosystem, the water will evaporate, condense on the top of the container and then "rain" back into the soil/sand, simulating the water cycle in nature.
Project Deliverables
After performing the experiment, students should submit:
Report
- Introduction: In this section, students should present the theme of the report, explain what the water cycle is, why it is important and the objective of the experiment performed.
- Development: Students should explain in detail what they did to perform the experiment, the materials used, the step-by-step followed and how these relate to the water cycle in nature. In addition, they should present the observations made throughout the experiment and discuss their results.
- Conclusion: Students should summarize what they learned from the experiment, what they concluded from the results obtained and the skills that were developed throughout the project.
- Bibliography: Students should indicate the sources of information they used to carry out the experiment and to prepare the report.
Project Presentation
Groups should organize a project presentation, either through an exhibition of the experiment or an oral presentation. During the presentation, they should explain what the water cycle is, why it is important, how they did the experiment and what they learned from it.
The workload for completing the project is 5 to 10 hours per student, with a one-month delivery date.
