Homemade water filter

Lower Secondary - 11-14 years - Duration: 2 sessions of 45 min.

Introductory question

How can we use everyday and recycled materials to build a device that helps clean dirty water?

Explanatory summary

This activity turns students into environmental engineers. We will explore the principle of filtration to address a global challenge: access to clean water. Teams will design, build and test prototype water filters, using layers of different materials to purify cloudy water. The goal is not only to learn about science and technology, but also to develop a greater awareness of the importance of water as a resource and our social responsibility to protect it.

Skills to be developed

Cognitive: Analysis (compare materials), Creation (design prototypes), Evaluation (judge the effectiveness of the filter).
Socioemotional: Collaboration (teamwork), Perspective taking (understanding global challenges).
Internships: Design and prototyping, Scientific observation, Data recording.

Linked standards: UNESCO (SDG 6), Project Based Learning (PBL).

Learning objectives

Design and build a working prototype of a water filter with at least three different layers.
To compare the effectiveness of different combinations of materials in water clarification.
Record and analyze qualitative observations (clarity, color, odor) of the water before and after filtration.
Argue the relationship between filtration technology and the goal of achieving more equitable access to clean water.

Materials

Economical (Recycled)	Standard	Pro
Plastic bottle, pieces of old cloth, small stones from the yard, sand.	Cotton, gauze, activated carbon (aquarium), fine sand and gravel.	In addition to the standard: pH test strips, turbidity meter (TDS) or a colorimetry app.

Security: Filtered water is NOT potable and should not be consumed. Adult supervision required when cutting materials.

Step-by-step procedure

Phase 1: Research and Design - In teams, research and draw a sketch of your filter. Decide on the order of the layers of materials and justify your choice. (20 min)
Phase 2: Construction and Testing - Build the prototype according to your design. Prepare a sample of «dirty» water (with soil and leaves). Pour it slowly into the filter and collect the result. (45 min)
Phase 3: Analysis and Discussion - Observe and record the changes in the water. Compare your results with those of other teams. Discuss as a group which designs worked best and why. Connect the experience to the global problem of access to water. (25 min)

Formative evaluation

Reflection questions:

What material do you think was most important in your filter and why?
If you had to improve it, what would you change in your design?
How does this small technological solution relate to the lives of millions of people around the world?

Evidence: Design sketch, functional prototype, recording of observations, participation in discussion.

Rubric (4 levels)

Criteria	Initial	Basic	Advanced	Expert
Prototype Design	The filter has less than 3 layers or is unstable.	The filter is functional and has 3 layers.	The design justifies the order of the layers.	The design is innovative and justifies the choice of materials.
Analysis of Results	It vaguely describes the result.	Compare the water before and after.	Analyze and explain why the water changed.	Analyzes, proposes improvements and cites possible sources of error.
Social Connection	Mention that water is important.	Relate the filter to the need for clean water.	Explain the connection between technology and access to water.	Argues about the role of engineering as a tool for social equity.

Differentiation

Supports: Provide visual templates with layer examples to guide the design.
Extensions: Research and build a simple solar still for more complete purification.
Challenges: Design a filter for a specific contaminant (e.g. oil) or to maximize water flow.

Connections to daily life

Health: Understand how filtration prevents waterborne diseases.
Environment: Reflect on river pollution and the importance of using sustainable materials.
Values: Foster empathy, equity and social responsibility in addressing a global problem.

Safety and sustainability

It is essential to remember that this experiment is a simulation. Under no circumstances should filtered water be drunk., as it does not kill bacteria or viruses. For sustainability, prioritize the use of bottles and fabrics already used to minimize waste.

Guide generated with the support of IA. License: Creative Commons Attribution (CC BY 4.0).

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