Introduction to Redox Reactions
Lesson 2 of 7
Objective: Students will be able to define and explain terms related to redox reactions.
In the last lesson students learned that two pieces of metal stuck in a lemon could light a small LED. In this lesson students will begin to learn why this is using their textbook to answer carefully scaffolded reading questions.
This lesson aligns to the NGSS Practices of the Scientist of Obtaining, evaluating, and communicating information because students spend the majority of the class time obtaining information from text. They also spend some time communicating what they have learned.
It aligns to the NGSS Crosscutting Concept of Patterns because studying redox reactions reveal a pattern of loss and gain of electrons at the nano-scale that help to explain why the light bulb lighted in the previous lesson.
This lesson also aligns to the HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties because redox reactions focuses on a chemical reaction in which the outermost electrons are transferred from one element to another.
There is no specific prior knowledge or skills that students should have related to this lesson.
There are no special materials needed for this lesson.
Do Now: I begin class by asking students to provision themselves. I note that they will need something to write with, notebook paper, a chemistry book, and the Electrochemistry Reading Questions for this unit. They are acquainted with where to find books and reading questions, and the other materials are in their backpack.
I reason that this is a good way to start class because I want to contextualize their work, which means I do not want them immediately jumping into their work, but I also want them to make progress on today’s work.
Activator: I start this contextualization by showing 2 videos that describe 1) how electricity is made and 2) how that electricity lights a conventional light bulb.
For the first video I ask students to think about how electricity is generated. What is needed to make and deliver electricity? For the second video I ask students to think about a conventional light bulb lights up.
After the first video I ask students to name what is needed in order for us to use electricity to charge our cell phones. As a group, students name that an energy source is needed, but also a mechanical or chemical process is needed to turn the power source into usable electricity. A way to transmit this energy is also needed. For the second video, students name that electrons are bumping into tungsten atoms and this causes the filament to glow. I point out that the video includes footage of the filament breaking, which is pretty dramatic. I also note that electricity, then, can be thought of as the flow of electrons.
My goal with this part of the lesson is to contextualize the reading and writing students will do during most of the class.
Mini-lesson: Once I have contextualized the lesson, I explain to students that today’s class is dedicated to students obtaining information from their textbook about a type of reaction called redox reactions. Redox reactions are actually a combination of two reactions—an oxidation reaction, and a reduction reaction. I note that because you cannot have one without the other, the term redox is used to combine the two reactions into one word.
I note that this work is important for student mastery of this unit. I note that today we will be covering factual information that will be on the unit test, and on other days we will look at redox reactions mathematically.
This instructional choice reflects my desire to give students practice obtaining information from their text book, which is a key college skill.
Student Activity: During this time I let students work independently or in small groups on the Electrochemistry Reading Questions. As long as students are working to obtain information, I am satisfied. Many students are comfortable reading the textbook and finding answers. I walk around the room and encourage students and answer their questions. Some students just like to check in with me to make sure that the answers they are recording match what I was hoping they would extract from the text.
It is important to the culture of the classroom that I am engaged in their work. I learned a long time ago that when students are doing independent work that this is not a good time for me to correct papers or engage in other professional activities. When I show my students that I am engaged in the material and in students accessing this information, I find that the classroom culture feels more engaged and on-task. My actions speak volumes to students.
Catch and Release Opportunities: One of the common questions I receive is “What is a watt?” I reply “Whaat?” It lightens the mood, and I note to individuals that I will address this all at once. I stop class and note that watt is not in our text book. I ask if anyone has heard of a watt? Some people have. Some of the responses I get are around light bulbs, the work kilowatt, and a hundred-watt smile. I smile, and then note that a watt is a unit of electrical power. I note that electrical power is calculated by multiplying amperage by voltage.
To wrap this lesson up I first engage in individual discussions around the question "What did you learn today?" as shown in this student recap video. I am curious to see how well students grasp the big picture.
As I suspected, the student needs some help relating the idea of a battery to the idea of electron flow. I know I have a lesson in the future that addresses linking the details from this lesson to the bigger picture of how a battery works, so I am not too concerned.
I then cold call students to share some of their answers. Judging from the responses, I feel that students were able to extract the information I was looking for. This student work is typical of what was produced in class today, though some students need to complete this work for homework.
I note that in the next class we will begin to analyze redox reactions mathematically.