Lesson 4: What makes atoms stick together?
HS Physical Science Unit: Why do some things get colder (or hotter) when they react? This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 1 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? Getting Ready: Materials Preparation Materials For Each Group
Preparation of Materials (15 min.)
● A variety of connection toys ­ definitely magnets, possibly velcro, glue/tape, Tinker Toys, Legos, etc. ● Ensure that enough connection toys are available for each group to have access to three at a time, so that students can compare them to each other directly. Materials For Each Student
Safety
● 4.1 ­ Student Activity Sheet (1)
● No special precautions
Getting Ready: Teacher Preparation Student Background Knowledge
Alternative Student Conceptions
PS1.A from the FRAMEWORK: “Each atom has a charged substructure consisting of a nucleus, which is made of protons and neutrons, surrounded by electrons.” This should have been covered in a prior high school physical sciences unit focused on HS­PS­1, and is necessary for students to think about what types of connections might exist between atoms and how this relates to familiar macro­level connections. Students may think that atoms connect together much like a stick­and­ball type model and fit this into mental models of ionic and covalent bonding. Differences in bonding are hinted at in this unit and ionic/covalent terminology is introduced in the next unit. Linking Our
Understanding to
Scientific Terminolog​
y
● Bonds ● Force This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 2 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? Learning Plan: What is this thing made of?
( Three 40-min
periods )
Teacher Supports & Notes 1​
1. (5 min) Begin with a Consensus Building Discussion ​
to help re­orient students in the storyline. Use the following prompts to help students articulate what they figured out in the last lesson. 1:​
The goal of this discussion is to put students in the driver’s seat. Use the prompts to help students recall and restate what we as a class figured out in the last lesson. Their ideas should motivate what we are going to need to do next, in this lesson. Suggested Prompts: ➔ What did we discover last time about where the energy is coming from when the salt dissolves and how the energy is used? ​
Listen for ​
student responses 2​
that refer to what we figured out last time, such as: ➔ We figured out that the energy coming from the environment when a salt dissolves must be used to break the connections between atoms. We wondered what this connection is, and why we need energy to break it. Additional Guidance 2: ​
If students struggle to recall the previous lesson, prompt them to consider what phenomena they examined or what activities they engaged in. Refer them to their models. ​
2. (15 min) Next, shift to a Sharing Initial Ideas Discussion 3​
. Use the following prompts to guide ​
students to articulate what they think they should focus on​
in today’s lesson. It may be best to give students time to generate responses to the first prompt in the space provided on the student sheet before moving on. Strategies for this Consensus Building Discussion Strategies for this Initial Ideas Discussion 3:​
In this discussion, students should lay out the path for the activities they will engage in today. Use the prompts to ensure that students do this heavy lifting to generate ideas. If students especially struggle to discuss atomic structure, an extended “refresher” discussion may be Suggested Prompts: ➔ What are different ways we know two things can be connected together? ➔ What do we know about atomic structure? ➔ Are any of those connections we listed like those between atoms? Listen for ​
student responses​
that mimic the next step in the storyline, such as This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 3 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? necessary. ➔ Because we wondered about what the connections are between atoms and struggled to say which of these items represent the connection between atoms, it might be helpful to look at examples of how two objects can stick together. If we know what kind of connections are between atoms, this could help us figure out why when two atoms come apart, they take up energy. 3. (20 min) Students now have an opportunity to explore the connection toys. Divide them into ​
groups of 3­4 4​
and ask them to complete the “Investigation” table on the student sheet. In this table, they will identify how each type of connection (tape, magnets, etc.) is similar and different to the connection between atoms. Make it clear that they will share their table with the whole class. Encourage groups to come to consensus on which connection is most similar to that between atoms before presenting. Suggested Prompts: ➔ Listed in teacher version of student sheet. In general, encourage students to consider the pros and cons of each type of connection. Listen for ​
student responses​
such as: ➔ Listed in teacher version of student sheet 4. (30 min) When students have completed the activity, bring them back together as a whole group. In this Building Understandings Discussion, have groups present their suggested models for how atoms are connected to each other. The students that aren’t presenting can record their classmates’ ideas in the “Presentations” section of the student activity sheet. At this point students should only ask questions about each other’s models, rather than making criticisms. Differentiation Strategies and Alternate Activities 4:​
Consider pairing students with weaker mental models of atomic structure with those who have stronger understanding, and ask those with weaker models to speak for their groups to ensure that they understand and are on­board with the group’s pre­presentation consensus model. This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 4 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? 5. (20 min) After students have shared, ​
revisit the question, “What have we figured out so far?” Use the following prompts to guide this Consensus Building Discussion. Suggested Prompts: ➔ Which arguments did you find most convincing? Why? ➔ In a given model, can we match different parts of the model to the parts of an atom? ➔ Can the forces in the model account for how atoms still pull on each other when pulled apart? ➔ What role does energy play in our model? In an atom? Listen for ​
student responses​
such as: ➔ The positive nucleus of the first atom is pulling on the negative electrons in the second atom. ➔ This is just like how the positive end of the magnet attracts the negative end of another magnet. ➔ In order to break atoms apart you have to put energy in just like it takes energy to pull apart two magnets that are attracting toward each other. ➔ The force you apply to break atoms apart has to be stronger and in the opposite direction of the force attracting the two atoms together. ➔ The energy to pull atoms apart must come from something in the environment, like a person’s hands on a magnet. When consensus has been reached that magnets are the best model we currently have for how atoms are connected, name this connection as a bond. This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 5 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? 6. (20­25 min) Give students time to work in their groups and, in the space provided on the activity ​
sheet, justify the choice of the consensus model in their own words and draw it for themselves 5​
, explaining why energy is needed to break the bonds. 5: ​
Models should show arrows between nuclei and electrons of opposite atoms in an initial view, and may use different arrows to show an input of energy and/or exertion of force to pull them apart. 7. (5­10 min) ​
​
Before dismissing students, ask groups to finish the last prompt together: “Identify 3­5 shortcomings of the physical representation chosen to represent the connection between atoms.” Discuss as a class if there is time, but consensus is not the goal here ­ the question of how our model is incomplete will be picked up in Lesson 5. Suggested Prompts: ➔ What did you write down in the “differences” column when examining magnets? ➔ What arguments did your classmates bring up to say why magnets shouldn’t be our model? Listen for ​
student responses​
such as: ➔ Magnets have north and south poles, whereas atoms have a positive nucleus at the center and negative electrons surroundings it. ➔ Atoms can’t just be pulled apart by hand like magnets. Thermal energy is involved somehow? Example / Sample ➔ The electrical force between atoms in a bond may not be the same process as the force between magnets, because not all elements are magnetic. ➔ Magnets are much larger than atoms. ➔ Not sure how atoms can both attract and repel (collide and bounce off) if there aren’t separate positive and negative ends. This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 6 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? Alignment With Standards Building Toward Target NGSS PE
Building Toward Common Core Standard(s)
● HS­PS3­5. ​
Develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction. ● ELA standards: none ● Math standards: none Unit and Lesson Authors: Aliza Stein​
​
([email protected]), Learning Sciences PhD student, Northwestern University Dan Voss​
​
([email protected]), Master’s of Science in Education student (physics and chemistry), Northwestern University Editors / Reviewers: 1​
1 & 2​
1 Tara McGill ([email protected])​
, Michael Novak ([email protected])​
, Brian J. Reiser ([email protected])​
[1 ­ Northwestern University School of Education and Social Policy, Evanston, IL; 2 ­ Park View School, Morton Grove, IL] This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 7 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? What Makes Atoms Stick Together? Class brainstorming Make a list of different types of connections. How can we physically attach one object to another? _____________________________________ ______________________________________ _____________________________________ ______________________________________ _____________________________________ ______________________________________ _____________________________________ ______________________________________ _____________________________________ ______________________________________ _____________________________________ ______________________________________ Investigation Use the connection types from the above brainstorming in the first column of the table. For each type of connection identify its strengths and weaknesses as a model for the connection between atoms and explain your reasoning. Make sure to use what you know about the substructure of atoms in your response. Circle the one that your group thinks is most useful as a model for the connection between atoms. Type of connection How is this connection similar to the connection between atoms? How is this connection different from the connection between atoms? Aliza Stein (​
[email protected]​
) and Dan Voss (​
[email protected]​
), 2015 This work is licensed under a Creative Commons Attribution 4.0 License http://creativecommons.org/licenses/by/4.0/
1 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? Type of connection How is this connection similar to the connection between atoms? How is this connection different from the connection between atoms? This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 2 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? Presentations Use this space to record brief notes about other groups’ models and any questions you might have on them. Brief description of model Questions for the presenting group This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 3 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? Summarizing group consensus Which model did we agree on as a class? Why is this model the best representation of the connection between atoms? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Draw a model of the connection between atoms, based on the physical representation we selected today. Use this model to answer the question, “Why is energy needed to break the connection between atoms?” This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 4 Lesson 4: What makes atoms stick together? Why do some things get colder (or hotter) when they react? Use the model you just drew to explain why energy might be needed to break the connection between atoms. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Identify 3­5 shortcomings of the physical representation chosen to represent the connection between atoms. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ This work is licensed under a Creative Commons Attribution 4.0 License ​
http://creativecommons.org/licenses/by/4.0/ Version Date 3/29/2016 5