Determining Whether An Object Is Actually Gold

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SUMMARY

The discussion focuses on determining whether a gold crown is pure gold or a gold-copper alloy based on its mass readings in air and water. The crown's mass in air is 14.7 kg, while submerged in water, it reads 13.4 kg. Using Archimedes' principle, the buoyant force, which equals the weight of the displaced water, is calculated to be 1.3 kg. By applying the densities of gold (19.32 g/cm³) and copper (8.96 g/cm³), participants can derive the ratio of gold to copper in the crown if it is indeed an alloy.

PREREQUISITES
  • Understanding of Archimedes' principle and buoyancy
  • Basic knowledge of density calculations
  • Familiarity with mass and volume relationships
  • Concept of specific gravity
NEXT STEPS
  • Calculate the volume of the crown using the buoyant force and water density
  • Learn about density calculations for mixtures and alloys
  • Explore the concept of specific gravity and its applications
  • Investigate methods for determining the composition of metal alloys
USEFUL FOR

Students in physics or chemistry, jewelers assessing metal purity, and anyone interested in material science and alloy composition analysis.

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A gold crown hangs from a spring scale reading it's mass as 14.7 Kg. When the crown is submerged in water while still hanging from the spring scale, it's mass now reads 13.4 kg. Knowing that its either all gold, or a gold and copper compound, figure out which of the two it is. If it is a gold and copper compound, what are their ratios. Density of Au=19.32, Density of Cu=8.96.

I'm stuck, not really even sure where to start. :(. Any tips or help would be greatly appreciated. I do not by any means want anyone to do this for me. A nudge in the right direction would be great.
 
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A law of buoyancy says the difference between the two weights is the weight of fluid displaced. Is that enough of a nudge?
 
More simply put: The buoyant force is equal to the weight of the displaced fluid.
 

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