# Rate of Filtration

## Objective

Determine a mathematical model which describes the rate of filtration of water through a medium.

## Difficulty

Procedure: Easy

Concept: Easy

## Concept

Suppose you determine the rate at which water filters through a particular brand of coffee filter. How does this rate vary with the thickness of the filter (stacking filters)? If necessary, brushing up on your Excel (or Open Office) skills for data analysis would be a good idea.

## Hypothesis:

What type of model do you think would model this situation? (linear, exponential, etc.)

## Materials:

- Coffee filters
- Water
- Beaker/Measuring Cup
- Timer

## Procedure:

- Adequately wet a coffee filter. (the purpose for this is so that water is not absorbed by the coffee filter)
- Attach the wet coffee filter (the medium) to the top of a beaker with a rubber band so that the coffee filter spans the top of the beaker. Be sure to leave room for water to sit and filter.
- Record the time it takes for the water to filter.
- Repeat steps 1-3 for thicker mediums. (2, 3, 4 coffee filters and so on)
- Enter the data into Excel.
- Compare your data with your hypothesized regression.

Be sure to collect enough data points. You may need as many as 20 coffee filters for your last data point. Also, be sure to run the experiment several times to demonstrate consistency

## Analysis

Did the hypothesized regression fit the data points well? If not, try other regressions and analyze how well they fit the data.

## Conclusion

Do the results support your hypothesis? Give reasons on why the results did or didn't support the hypothesis? Are there other factors which affect filtration rate? Can you design other experiments to test these factors?

## Extensions

Do the results in this experiment only work for water and coffee filters? See if you can find other mediums and other liquids to come up with more generalized hypotheses.