Lab Report #8 Alloy Penny Experiment PDF

Preview

Summary

Download Lab Report #8 Alloy Penny Experiment PDF

Description

Lab Report #8: Alloys-Penny Experiment By: Trevor Gumbs Date: 11/8/20

Objective: The goal for this experiment is to determine the percentage of copper and zinc in an old and new penny with an x-ray fluorescence (XRF) spectrometer. Introduction/Theory: Alloys are homogeneous mixtures of two or more metals that combined together by metallic bonds. An alloy is created from copper pennies which is changed into silver and then into gold coins. Alchemists in Europe and the Middle East attempted to find methods of obtaining gold out of lead and copper since ancient times. Even though their methods failed, the outcome still looked like gold but wasn’t gold. The lookalike gold is made up of copper (Cu) and zinc (Zn). The US treasury department decided to change the composition of the penny after 1982 when the price of copped began increasing. The composition of the penny before 1982 was 95% Copper (Cu) and 5% Zinc (Zn) but the composition then changed to about 97.5% Zinc (Zn) and 2.5% Copper (Cu) since 1982. Brasses and bronze are the most known alloys formed from copper and zinc. Brasses has a bright gold-like look and is used in coins and many other items such as decorations and musical instruments such as horns and bells. Bronze is known as one of the oldest materials used by humans since the 3300- 1200 BC. It is great for casting complicated and exquisite art work such as statues/sculptures and jewelry as it is also in tools, household items and armor. They are also are harder and more corrosion resistant than brasses.

Materials: -1982 penny -2017 penny -2 100ml beakers -15ml vinegar -5ml saturated salt solution -tongs -10ml 3M sodium hydroxide -4g granular/powdered zinc -hot plate -water -paper towels -digital scale

Procedure/Observations: First, both pennies were dropped about 10 inches above in order to hear the difference within the sounds they make. The older penny made a louder sound than the newer penny. Next, the 15ml of vinegar and 5 ml of saturated salt was added in a 100ml beaker. The pennies were then deposited into the beaker for about 10 minutes to be cleansed. The pennies were then removed with metal tongs and added to a beaker with water to be rinsed of and then wiped with a paper towel and then weighed. Next, 10 ml of 3M sodium hydroxide and 4g of Granular/powdered zinc was added to a 100ml beaker and then heated on a hot plate set to 150 degrees until near boiling and then removed with the use of metal thongs. The pennies were then added to the solution for about 10 minutes until it turned silver. However, more 3M sodium hydroxide was added because it evaporated and and then re-heated on the hotplate at 210 degrees. The pennies were then removed and rinsed off for about 3 minutes and then dried and weighed. Both pennies were then heated on the hotplate at 300 degrees at 1 minute per side until it turned gold and then rinsed off with cold water and then dried and weighed.

Data and Calculations

Conclusion/ Sources of error: The objectives of this experiment were met because the instructions were followed thoroughly. However, because the #M sodium hydroxide evaporated, more was added to the solution and reheated at 210 degrees with the use of the hotplate.

Questions:...