Module 3
1. Module 3
1.4. Page 2
Module 3—Electrochemical Reactions
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Have you ever noticed when you look at the jar of spare change in your house that pennies really loose their shine? Is there a relationship between the age of the pennies and their loss of luster (shininess)? Look at the dates on some of the pennies in your household change jar or in your pocket to see if there is a connection between a penny's age and its luster.
TR 1. Write a hypothesis describing a relationship between a possible factor and the loss of luster by copper as demonstrated by the pennies in your household change jar. Submit a copy of your hypothesis to your teacher for feedback.
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Read page 556 of the textbook.
Do you think the change in copper observed in the pennies or in the photograph of the copper statue at the beginning of this lesson demonstrates an electrochemical process? Start your analysis of these systems by writing the chemical formula for the forms of copper that have the appearances you observed. Can you describe the differences between the chemical formulae for these forms of copper? Do the differences in the chemical formulae you have written fit the description of an electrochemical process (a type of chemical change that involves a transfer of electrons)?
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In previous science courses you learned that the net charge given to an atom or group of atoms is due to the quantity of protons and electrons the atom or group possesses. Electrochemical changes involve a transfer of electrons. Therefore, a change in the net charge of a substance often indicates that the substance has undergone an electrochemical change.
In the case of copper, its various forms have distinct colours, and the change in copper from its elemental form (net charge zero) to copper(II) ion (net charge 2+) involves a loss of electrons to create the positively charged copper(II) ion.
Some of the first investigations involving electrochemical reactions occurred as society began to work with metals. Read pages 558–559 of the textbook to see how metallurgy developed some of the terminology you will use throughout this unit.