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 continue to develop an understanding of how to count atoms and balance equations by taking a quiz as a summative assessment. In addition, student will start to see 5 different chemical reaction types (discussed in the Explore section) that show that conservation of mass can happen in a variety of ways.
Science and Engineering Practices (SEP)
Students will engage in the SEP of Asking Questioning and Defining Problems (#1) during this lesson. As students are learning the different types of reactions they will be required to ask questions and make observations which are used to determine patterns that occur in each type of reaction.
Crosscutting Concepts (XC)
During this lesson students will recognize that patterns occur in science. Students are expected to see that patterns exist in each of the 5 types of reactions and be able to recognize each reaction based on these patterns an attributes.
At this point in the unit students have had a sufficient amount of practice balancing equations and recognizing evidence of a chemical reaction. The main focus of the Chemical reaction quiz #3 is to check for understanding of The Law of Conservation of Mass, balancing chemical equations and reaction terminology (Reaction Quiz #3 key). The quiz should take no longer than 20 minutes.
Most of the students should have a sufficient understanding of balancing equations based on homework assessment over the past couple of days. The area where students struggle most is their comprehension of the Law of Conservation of Mass (reaction quiz 3 SW)and (Reaction quiz3 SW 1). Students tend to struggle with these questions for 2 main reasons: (1) they have little exposure to the Law of Conservation of Mass prior to high school chemistry and (2) they have a difficult time conceptualizing that matter can rearrange during a chemical reaction and the products can have different properties (such as a solid turning to a gas) but still maintain a mass that equals the reactants. I believe this difficulty stems from the fact that students still believe only matter that is visibly seen has mass, and matter such as gases no longer are part of the mass of the reaction.
Below are samples of two students' work.
After students finish the quiz I have them turn it in and pick up the graphic organizer they will use for the concept attainment. Since the quiz took half the period, there is only time for 1 of the five reactions. The other four will be address during the next lesson. I find that having them do one first is good because it allows students time to process what to do during Concept Attainment.
Background Information on Concept Attainment
Concept Attainment is a strategy that encourages critical thinking skills. It works by providing a target concept or idea that is not communicated to the students. The teacher presents examples (verbal or pictures), and the students guess the concept by figuring out the common attributes. Concept attainment is a good strategy for types of chemical reaction because they have clear characteristics and are easily defined by their attributes. Students are able to build their own idea about the concept before being told which provides a more personal and lasting understanding of the concept.
Procedure for implementing Concept Attainment
It may take 5 minutes to get through all the example. Once everyone has processed the information, and developed a personal explanation of positive attributes of a synthesis reaction, I have them share their explanation with another person. This provides a comparison to another person’s ideas. By the end of the lesson most students have attained a good understanding of what pattern is present in synthesis reaction. However, some student have a difficult time articulating it in writing, so sharing thoughts with another student can aid in the process of stating a pattern in words.
After several minutes of partner time it’s time to assess what students have come up with. For the last 5 minutes of class I ask for volunteers to explain what pattern is present in all synthesis reactions.
If students provide something close to these 3 typical responses I feel as though students understand what attributes a synthesis reaction contains. In five minutes the majority of the class can provide a response and provide me with enough feedback to see if further review of a synthesis in needed for the next period.