"I eat and drink chemicals? No way!" Students often associate lively and explosive chemical reactions with the study of chemistry. What students don't always realize is that chemistry and chemicals are constantly interacting and reacting around us. This lesson is a fundamental lesson that introduces the concepts of chemical names and chemical formulas, so students can access the rigor contained within these Matter and Its Interactions (MS-PS1) performance expectations:
1. Develop models to describe the atomic composition of simple molecules and extended structures (MS - PS1-1).
2. Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred (MS - PS1-2).
3. Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved (MS - PS1-5).
In order for students to meet these performance expectations, they need to be able to recognize that chemicals are made of specific atoms in specific proportions and following certain patterns that contribute to the properties of those chemicals: macroscopic patterns are related to the nature of microscopic and atomic-level structure (CCC). As students investigate different chemicals used in daily life, they identify common names, chemical names, chemical formulas and uses of chemicals used in daily life by gathering, reading, and synthesizing information from multiple appropriate sources (SP8).
In order to ENGAGE students in this lesson, students read this Dihydrogen Monoxide Warning (or your own warning) with the purpose of determining three influential reasons that the public should be concerned about this "dangerous" chemical. In pairs, students extract and report out their reasons for public concern. To further warm students up and engage them, students conduct additional research using these online sources: Dihydrogen Monoxide Research Division Site and Ban Dihydrogen Monoxide! Site. Based on their research, students write a short (paragraph or less) press release to inform the public about the potential issues related to dihydrogen monoxide. Visit this section's reflection: Authentic Writing Opportunities in Science for more about writing press releases. A few student pairs share their press releases to further build the hype around this chemical. At this point, suggest that it is time to learn more about the chemicals around us in order to see just how dangerous the world really is.
Teacher Note: It is important that students use only the provided sites for this engagement activity. If students search for dihydrogen monoxide, they quickly learn that this chemical is simply water. Since the purpose of this engagement activity is to illustrate how chemicals are all around us, and we interact with them constantly, this element of surprise needs to be maintained. In order to further promote and protect the element of surprise, invite students to be conspirators with you against the other class sections you may teach. Challenge them to spread the dangers of dihydrogen monoxide to the other classes rather than telling them the "secret".
The EXPLORE stage of the lesson is to get students involved in the topic so that they start to build their own understanding. To help students explore common chemicals around us, they use web-based resources and the Common Chemicals Webquest handout to collect data about nine different chemicals. Students identify the common name, chemical name, chemical formula, uses and types/number of atoms for the chemicals and record in the chart. Students will ask about dihydrogen monoxide and how it relates to the chart. Direct students to the example provided on line one. They are surprised to see that it is simply water!
This process is like learning a new language, and many students can use support when translating chemical formulas into the types/number of atoms. To facilitate this process, a mini-lesson using the talking points outlined in the video below prior to investigation may aide in the inquiry process for students. An alternate strategy to address this student need is to circulate to each student or group of students to check for progress and provide individualized mini-lessons if needed.
The EXPLAIN stage provides students with an opportunity to communicate what they have learned so far and figure out what it means. This stage of the lesson presents a great place for a quick formative assessment. Students benefit from an individual or class review of the data collected in the Common Chemicals Webquest chart in which they should be actively explaining how they determined the chemical formulas and/or the types and number of atoms that comprise those chemicals. During this review, challenge students to record their data accurately and precisely. For example:
1) Each element symbol starts with a capital letter. Each time there is a capital letter, this shows that a new element is present.
2) Some element symbols have only one letter, but they can have two or three letters.
3) Subscripts (the little number in chemical formulas) denote how many atoms there are of the element directly preceding the number. These numbers are written slightly below the line of text.
4) Chemical formulas can be written in different orders but are still the same chemical.
5) Parentheses act to "clump" some atoms together. These clumps may be followed by a subscript that denotes how many total groups of atoms there are.
Teacher Note: Student readily use search engines to complete the webquest chart. Providing a curated list of previewed sites makes the research process more efficient and more accurate. Several previewed sites are listed at the top of the Common Chemicals Webquest handout.
The EXTEND stage allows students to apply new knowledge to a novel situation. The novel situation in this case is for students to explore chemicals of their own choosing using the Common Chemicals Webquest chart. This extension provides two opportunities: students to learn about chemicals of interest which serves to build additional engagement and also gives additional practice with translation of chemical formulas into numbers and types of atoms that make up the chemical. For an extension example, view: Common Chemicals Webquest - Student Work.
The EVALUATION stage is for both students and teachers to determine how much learning and understanding has taken place. Since this lesson is a skills building block lesson that leads to other, more rigorous concepts, a short "check for understanding" assessment like this one is sufficient: Chemical Formulas Quiz 1. For a connection to Earth and Space Sciences, this Chemical Formulas Quiz 2 uses mineral samples that students can observe while determining chemical formulas and/or the types and number of atoms that comprise those chemicals.