Monomers make Polymers
Lesson 18 of 30
Objective: Students will understand the how the process of dehydration synthesis allows the carbon molecule to form macromolecules that perform vital functions in cells.
Warm-Up: What are some examples of things that are complex yet made up of simple units?
Ask this Warm-Up question to activate students’ thinking about the relationship between simple units and more complex things. Encourage students to not only think about science, but consider everything that is complex yet made of simple units.
Be careful not to accept student responses too quickly because students who require a little more time to process a question and formulate a response may grow to feel that it isn't worth their time to engage in the thought process because class discussions move on before they are ready to contribute or even listen to other students’ thought. Give students 1-2 minutes to engage in the thought process before accepting the first response from a student.
Allow students to share their responses. If students struggle with this question, be prepared to share some examples, preferably non-science examples since many students will relate more to a non-science example. For example, a cell phone is made up of small units called “cells” but it is very complex. A computer is made up of bytes but it is very complex, as well. Listen to all responses before informing students that they will learn more about the relationship that exists between simple units and complex units in today’s lesson.
Introduce New Material
Begin the lesson by introducing the vocabulary associated with the lesson: element, monomer, polymer, dehydration synthesis, hydrolysis, macromolecule
Say each word aloud and ask students to repeat the term after you. Clap out the syllables for the terms with 3 or more syllables. This helps students hear the word parts of more complex words so that they can pronounce them correctly. Vocabulary acquisition includes being able to pronounce new words and this simple practice helps all students become more adept at correct pronunciation of new words.
Instruct students to add the bold terms to their Vocabulary Maps. Remind students that the bold terms contain prefixes, suffixes, Greek or Latin root words. Provide explicit instruction of each term when it arises during the course of instruction.
Inform students of the learning targets for this lesson:
- I can model and explain how monomers make polymers through the process of dehydration synthesis.
- I can model and explain how polymers are broken into monomers through the process of hydrolysis.
Display visual information as you instruct and ensure students are using Guided notes that you have provided or use a note-taking strategy that you have taught. Guided notes provide greater support for the different learning styles of students.
Provide explicit vocabulary instruction on the prefixes mono- and poly-. Ask student to think of other terms that use either of these two prefixes. Share the terms polygamy and monogamy and their meanings. These are terms that students may have heard before, which will help them retain the meanings of the prefixes. Introduce the terms monomer and polymer. It’s useful to depict the concept in multiple ways because students have multiple intelligences. Use of varied examples will help all students understand the relationship between the two structures:
- Look around the room and look for a student wearing a bead necklace or a linked chain. Use the necklace or chain as a teaching tool to help students comprehend that monomers are linked to make polymers.
- Share a video clip, Polymers are made from Monomers, source: Youtube.
- Call one student to the front of the room. Ask the class “Is this one student representative of a monomer or a polymer? Look for students to correctly identify that one student represents a monomer. Call 3-4 additional students to the front of the room and instruct the group to link arms. Ask the class “Is this representative of a monomer or polymer? Require students to explain.
- Show students plastic linking beads (connecting plastic infant toy) and ask students to explain the relationship between the beads using the terms monomer, and polymer and dehydration synthesis. Require students to explain their answer.
Once it is clear that students understand the relationship of monomers and polymers, explain how monomers link to make polymers through a chemical reaction called condensation or dehydration synthesis.
Ask students to attempt to decode the meaning of the term, dehydration synthesis based on what they already know about its prefixes, and Greek or Latin words. Guide them to identify the prefixes, de- and hydro(a)-, as well the root word, synthesis. Remind students that each of these word parts have been taught in other lessons as parts of other terms. Encourage students to use their vocabulary maps as a resource. Students should be able to roughly decipher that dehydration synthesis means “without (removing) water to make”. Once the meaning of the term is established, share an animation that shows students how water is removed to create a bond between two monomers.
Explain the process of hydrolysis, similarly. Ask students to attempt to decode the meaning of the term, hydrolysis based on what they already know about its prefixes, and Greek or Latin words. Guide them to identify the prefix hydro-, as well the root word, lyse. Remind students that each of these word parts have been taught in other lessons as parts of other terms. Encourage students to use their vocabulary maps as a resource. Students should be able to roughly decipher that hydrolysis means “adding water to break”. Once the meaning of the term is established, share an animation that shows students how water is added to break a bond between two monomers. Ensure that students note that these are reverse reactions.
End by sharing a rhyme intended to help students remember the difference between the two reactions:
Dehydration synthesis adds water (condensation) to MAKE, hydrolysis removes water to BREAK.
Reinforce the rhyme with a simple hand gesture putting fist to fist(thumbs touching) for condensation, then separating the fists with a downward motion for hydrolysis.
Perform a check for understanding and ask a few questions before moving into guided practice:
- If a pearl necklace were a polymer, what would be the monomer? What is the reverse reaction of hydrolysis?
- What does lyse mean?
- What does synthesis mean?
- What is produced besides a polymer during dehydration synthesis?
Display a Hydrolysis reaction diagram on an LCD projector. Instruct student to follow along using the same reaction that is on the guided notes. Instruct students to label their diagram as you “think aloud” to allow students to observe your thought process to identify and label the reactants, products, and type of reaction shown.
Inform students that they will engage in a atomic modeling activity, working in groups of two with the task to build two monomers of CH3OH. Students will remove a molecule of water to demonstrate dehydration synthesis and the formation of a polymer. Students will then simulate hydrolysis by adding water back to the polymer to break it down into two monomers.
Distribute hard copies of the Condensation and Hydrolysis Modeling Lab. Instruct students to perform a close read of the lab instructions and questions before beginning the lab. A close read will allow students to identify the lab's purpose and become more clear about the lab procedures. The close read will also act as preview for what they will be expected to know when peforming the lab analysis.
It may be helpful to have students underline or highlight the questions during the close read. This practice will help them progress through the lab more purposefully. Remind students to answer the questions from the lab using complete sentences. Give students 20-25 minutes to complete this activity.
As students work, walk around to observe student actions and conversations. Offer assistance in the form of guided questions as needed based on your observations. Students may struggle with the removal of the molecules that make up water so pay attention to students actions at this point in the lab.
Perform a “Condensation Quickwrite” where students write a 3-5 sentence constructed response as a formative assessment. Display the question, “How are polymers formed?”, on a LCD projector so that students will be able to refer to it as many times as needed as they develop their response to the question. Instruct students to use the content specific terminology in their responses.
The polymer quickwrite constructed responses demonstrate that students were able to explain the process of condensation.