Problem 18 - Chemistry: The Central Science

Question

You are hiking in the mountains and find a shiny gold nugget. It might be the element gold, or it might be "fool's gold," which is a nickname for iron pyrite, FeS \(_{2 .}\) Which of the fol- lowing physical properties do you think would help determine if the shiny nugget is really gold appearance, melting point, density, or physical state?

Step-by-Step Solution

Answer

Out of the given physical properties, density would be the most helpful in determining whether the shiny nugget is gold or fool's gold. Gold has a density of about \(19.3 \frac{g}{cm^3}\), whereas iron pyrite has a density of approximately \(5.0 \frac{g}{cm^3}\). Measuring the mass and volume and calculating the density of the nugget can provide a more accurate conclusion.

Step 1: Appearance

Comparing the appearance of gold and fool's gold can be a starting point but is not always reliable as they both have a metallic yellow luster. Gold has a more vibrant hue, while iron pyrite has a brassy color. However, appearance can be deceptive, and a definitive conclusion cannot be drawn from this physical property alone.

Step 2: Melting Point

The melting point of gold is around 1064 ºC, and for iron pyrite, it is around 1193 ºC. Melting points can be a good distinguishing factor, but considering that this is a field activity and it is not feasible to use melting points without specialized equipment, this physical property is not practical in this scenario.

Step 3: Density

Density is an essential property that can help in this matter. Gold has a density of about \(19.3 \frac{g}{cm^3}\), whereas iron pyrite has a density of approximately \(5.0 \frac{g}{cm^3}\). Measuring the mass and volume of the nugget, and calculating its density could help determine with more confidence if it's gold or fool's gold.

Step 4: Physical State

Considering that both gold and iron pyrite are found in solid-state under normal conditions, the physical state cannot be a suitable property for distinguishing between these two substances. In conclusion, out of the given physical properties, the density would be the most helpful in determining whether the shiny nugget is gold or fool's gold. Measuring the mass and volume and calculating the density of the nugget can provide a more accurate conclusion.