Counterfeit Coins Scientific Background
A coin collector has recently purchased a collection of Leif Ericson silver dollars from a website. After receiving the coins, the collector begins to suspect that the coins are not identical, and therefore, one or more of them is counterfeit or fake. The collector has submitted three coins to a laboratory to confirm their identities as either authentic and made of silver or counterfeit and made of aluminum or tin to determine whether the box is filled with authentic coins, counterfeit coins, or a mixture of the two.

Writing Task
Write a report for the coin collector that analyzes the obtained data on the three coins and explains how the data confirms the identity of each coin.
In your essay, be sure to complete the following tasks:
- Describe the results of the melting point test and explain how the melting point of a substance tells us information about what element it is.
- Summarize the observed physical properties of the three coins. Explain how the physical properties of the coins tells us about the elemental identity.
- Explain the chemical properties of the three coins. Describe how this confirms their identities.

(Documents A through D are related to this Writing Task.)

DOCUMENT A
Density of the suspected elements
Element
Density (grams per cubic centimetre)
Silver
10.49
Aluminum
2.70
Tin
7.29

DOCUMENT B
Chemical reaction test results
Object
Reaction with hydrochloric acid
Control - Pure silver Coin
No reaction
Control - Pure aluminum Coin
Reaction to form a grey solution
Control - Pure tin coin
Reaction to form a grey solution
Leif Ericson Coin 1
Reaction to form a white precipitate
Leif Ericson Coin 2
No reaction
Leif Ericson Coin 3
Reaction to form a grey solution

DOCUMENT C
Melting point test results
Object
Melting point (°C)
Control - Pure silver Coin
956
Control - Pure aluminum Coin
660
Control - Pure tin Coin
271
Leif Ericson Coin 1
960
Leif Ericson Coin 2
970
Leif Ericson Coin 3
656

Document D
Physical properties of the Leif Ericson coins
Coin
Observations
Leif Ericson Coin 1
Shiny, silver-colored, cold to touch, feels heavy in hand
Leif Ericson Coin 2
Shiny, silver-colored, cold to touch, feels heavy in hand
Leif Ericson Coin 3
Dull, silver-colored, cold to touch, feels light in hand