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A Norwegian, Johan Vaaler (1866–1910), has erroneously been identified as the inventor of the paper clip. He was granted patents in Germany[12] and in the United States[13]
Principles(s) Investigated:
- Density
- Surface Tension
- Cohesion
- Surfactants and Micelles
Standards:
Standards:
- 8a. Students know density is mass per unit volume.
- 8b. Students know how to calculate the density of substances (regular and irregular
- solids and liquids) from measurements of mass and volume.
- 8c. Students know the buoyant force on an object in a fluid is an upward force equal
- to the weight of the fluid the object has displaced.
- 8d. Students know how to predict whether an object will float or sink.
Materials:
100 ml beaker, large paper clips, dish soap, from home and lab storage room.
Student prior knowledge: What prior concepts do students need to understand this activity?
- Metal sinks in water.
- Paper clips displace water (take up space) equal to their volume.
- Procedure: Fill a 100 ml beaker as close to the rim as possible.
- Have students answer the Prediction Survey.
- Root question/prediction/hypothesis:
- How many paper clips can I put into the beaker before it will overflow?
- Students commit their # in the Prediction Survey.
- Ask students why they picked that # to reinforce "educated" guess.
- What do we know about paper clips/metals in water?
- Review predictions (average, and extreme number, reasons) Survey Responses
- Have students stand.
- Begin adding large paper clips one-by-one, counting aloud, and have students sit when their prediction number is surpassed.
Explanation:
Density: Paper Clips (7.75< Dsteel<8.05 g/cm3); Dwater = 1.00 g/ml.
Surface Tension: the force holding the surface water molecules together is unbalanced at the surface. (Hydrogen bonding between water molecules).
Cohesion: force of attraction water molecules exert on each other.Water Molecules
Surfactants: substances added to water to reduce the surface tension.
Micelles: regions of soap molecules aligned by polar interior attraction.
Questions & Answers: Give three thought-provoking questions and provide detailed answers.
Stop at "bulge" in top of the beaker of water. What is that? What is causing that?
Applications to Everyday Life:
Bridge Jumpers: Why do people jump from bridges to commit suicide. ie: The Golden Gate Bridge.
Acapulco Cliff Divers: how do they survive?
Washing Clothes and Surfactants/Micelles: how they work.
Back to the beaker of water: If we add soap will it take more or fewer paperclips? (you may redo the whole procedure: predictions, etc.) and Discuss the results and why.
Add a drop of soap to the beaker and watch it "drain" down to the rim.
That water will spill over when above level to the rim of the container.
Water is easy to go into (slow speeds assumed).
Photographs: above, original and from google search images.
Videos: from google video search.
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