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Testing Filters for a Chalk Dust Demo 4 questions
Testing Filters for a Chalk Dust Demo
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An art class models a filter for a box that contains suspended chalk particles. The chalk particles are small grains of solid calcium carbonate. The model treats each filter opening as a screen that blocks particles too large to fit through. The class wants a filter that retains at least 90% of the chalk particles and lets at least 12 L/min of air pass at the tested fan setting. Every trial starts with 200 chalk particles arriving at the filter.
| Filter | Chalk particles leaving filter | Airflow (L/min) |
|---|---|---|
| J | 40 | 18 |
| K | 14 | 15 |
| L | 4 | 9 |
Question 1
Calculate the percentage of chalk particles retained by filter K. Show how the particle counts enter the calculation.
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Question 2
Which filter meets both criteria in the test?
- J only
- K only
- L only
- K and L
Question 3
Explain why a filter can let air pass through while trapping some chalk particles. Refer to the relative sizes of the particles and the openings.
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A student tests K at a higher fan setting and counts 22 particles leaving. The class did not measure how many particles arrived at the filter in that trial.
Question 4
Explain why the new count alone cannot show that the higher fan setting reduced the percentage retained. State an additional measurement that would let the class compare the two settings.
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