A water filtration chemistry project shows how simple materials can make dirty water look clearer by removing suspended particles. In a homemade bottle filter, gravel, sand, and activated charcoal work together as water flows downward under gravity. This project matters because filtration is used in homes, treatment plants, and emergency water systems.
It also teaches how to measure results using evidence, such as changes in cloudiness before and after filtering.
The filter works by separating materials based on particle size, surface area, and attraction to charcoal surfaces. Gravel traps large debris, sand catches smaller particles, and activated charcoal adsorbs some dissolved substances that cause odor or color. Students can test variables such as layer order, layer thickness, flow rate, and the number of passes through the filter.
The filtered water may look clearer, but it is not automatically safe to drink because microbes and dissolved chemicals may remain.
Key Facts
- Filtration separates a mixture by passing it through a material that traps some particles.
- Gravel removes large particles such as leaves, small sticks, and clumps of soil.
- Sand removes finer suspended particles because the spaces between sand grains are small.
- Activated charcoal has a large surface area and can adsorb some odors, colors, and dissolved substances.
- Percent clarity improvement = ((initial turbidity - final turbidity) / initial turbidity) x 100%.
- Cleaner-looking water is not always safe water because filtration alone may not remove bacteria, viruses, or all dissolved chemicals.
Vocabulary
- Filtration
- Filtration is a separation process in which a mixture passes through a barrier or layer that traps some particles.
- Turbidity
- Turbidity is a measure of how cloudy water is due to suspended particles.
- Activated charcoal
- Activated charcoal is a porous form of carbon that can hold some molecules on its large surface area.
- Adsorption
- Adsorption is the process in which particles or molecules stick to the surface of a material.
- Variable
- A variable is a factor in an experiment that can be changed, measured, or controlled.
Common Mistakes to Avoid
- Drinking the filtered water, because the project filter can improve clarity but may not remove harmful microbes or dissolved pollutants.
- Mixing the layers together, because gravel, sand, and charcoal work best when each layer has a clear job in the flow path.
- Changing several variables at once, because it becomes impossible to tell whether layer order, layer thickness, or another factor caused the result.
- Judging clarity only by eyesight, because visual comparison is subjective and should be supported by a consistent test such as reading text through a water sample or using a turbidity scale.
Practice Questions
- 1 A dirty water sample has an initial turbidity of 80 NTU and a final turbidity of 20 NTU after filtration. What is the percent clarity improvement?
- 2 A bottle filter contains 4 cm of gravel, 6 cm of sand, and 3 cm of activated charcoal. What is the total thickness of the filter layers, and what fraction of the total thickness is sand?
- 3 Two student groups use the same dirty water. Group A puts gravel on top, then sand, then charcoal. Group B puts charcoal on top, then sand, then gravel. Explain how layer order could affect clogging, flow rate, and clarity of the filtered water.