Introduction to Chemical Reactions

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SWBAT write and answer questions based on the Law of Conservation of Mass.

Big Idea

Students use a reading strategy to create questions based on text that other students will answer.

NGSS Alignment and Introduction

10 minutes

Performance Expectation (PE)/Disciplinary Core Idea (DCI)

This lesson is aligned with HS-PS1-7, the uses of mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction; and DCI-PS1.B, the fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions. Students will be introduced to the Law of Conservation of Mass by reading several pages that introduce key concepts, such as types of reactions, matter is conserved during chemical reactions and balancing chemical equations.

Science and Engineering Practices (SEP)

Students will engage in Practice 1, Asking questions and defining problems, during this lesson.   Students will use a reading strategy called features story where they have to write questions based on the text they are reading.  They questions they write will also be answered by another student in the class.


Course Recommendations 

This is the first class back after winter break, so one of the perfunctory obligations is to provide students with next year’s course recommendations; therefore the first portion of the class is providing them with a brief overview of third year science classes offered.  I also provide a brief explanation of what classes will fit specific academic and future educational goals for each student.  Most students will take physics as a third year science, but I specifically speak with each student to provide a recommendation that fits their goals.  While I am speaking with students they will be required to work independently on the day’s assignment.


5 minutes

To get them thinking about chemical reactions I start class with a short think-pair-share based on the question: “What do you know about chemical reactions?”  After giving a brief overview of the course recommendation process, I ask them to right down a few things about what they know about chemical reactions.    After a minute or two of brainstorming I have them share with the person next to them, followed by a brief classroom discussion. 

Some of the concepts that came up during the group discussion;

  1. Reactions occur when two things are put together.  I follow this up with the question, “what happens when you add salt to water?”  Most students know that it is a physical change and can the salt can reappear through evaporation.
  2. Reactions occur when you burn something.  I followed this with the question, “what evidence leads you to believe a chemical reaction occurred after burning something?"
  3. Students respond to the previous question by say, “smoke, heat, carbon dioxide and water.”

I believe that students know more about chemical reactions than they might realize and discussing it with a classmate before a full group discussion helps validate their thinking and develops a good foundation for the reading assignment.

After the brief discussion I introduce the assignment for the period.

Explore (writing questions)

30 minutes

I don't consider this to be a traditional means of inquiry exploration, but since chemical reactions is such a new topic to many of my students the reading assignment is meant to provide information that can be used to scaffold further exploration, explanation and elaboration throughout the unit.

With this being said, after the brief discussion at the beginning of the class and explanation of course recommendations, I introduce the assignment for the period.  As students enter the class they know to pick up the days assignment.   

After explaining the assignment and walking students through a couple of examples of text features I instruct students that they should not create more than one question per page.  This ensures that they will read the majority of the pages and gather a better overview of the content that will be explored over the next few weeks.  

After explaining how to write questions, I let them know another classmate will be answer the questions they write and that it is important to make there questions as coherent as possible.

While they are working on this I will call up individual students to my desk for course recommendations.

Since students read at different paces, some students will finish the questions within 15 minutes while others will take 30 minutes. So instead of students sitting and waiting for all students to complete the question writing, I have them exchange papers with the first available person.  This alleviates students sitting around unproductively. 

Explore Part 2 (answering questions)

15 minutes

This component of the lesson makes students accountable for the questions they write by having a classmate answer the questions they wrote. This also provides further reinforcement of the Law of Conservation of Mass by having students revisit what that have read twice.  After students have written the questions and created a "featured story", they will take another students paper and use the same text to answer the questions on a separate sheet of paper.  This typically will take 10-15 minutes because they have already read the required pages (dependent upon textbook) and the questions are labeled with the page that contains the answer




To aid in grading I have the student answering the question write down the section, question they are and answering and the answer to the question.  They should also write the name of the person who's questions they are answering. If any one does not complete the question answering portion of the lesson, it becomes homework so the next class can begin with a discussion about what was learned.


Post-lesson Reflection

Most students have enough pride in their work that they are motivated to engage in good question writing. This may be due to the fact that other students will be reading their questions, but regardless of why, many students approached me and ask if the question they wrote is a good question.  That is a reason why I use this as a textbook reading strategy; it gets students enthusiastic about reading because it’s their “featured story”.  This strategy worked out very well because it provided them with a little background knowledge for the next lesson and introduced them to questioning as a means of building curiosity about a unknown topic. Having students write questions built a good foundation for the next lesson where students learned open-and closed-ended questions.