This unit is designed to answer the Essential Question, "How do particles combine into new substances? What evidence can show how the physical and chemical properties of the substances change?".
It particularly focuses on types of matter, physical properties, phase changes, and factors that affect physical properties. This unit's purpose is so much more than just the content, however. It's focus is scientific literacy. It stresses group discussion, discourse and utilizing text references when engaging in argument. Students utilize reading, writing, and speaking strategies in order to develop scientific literacy. It's scientific literacy immersion!
In this lesson, students gain an understanding of what elements, molecules, compounds and mixtures look like at the molecular level. Students use marshmallows to represent atoms and toothpicks to represent bonds. The purpose of the lesson is not for them to learn how to bond, but to notice what the particles might look like in each type of matter. Typically, this lesson requires two days from start to finish.
This lesson is geared to address the following NGSS and Common Core Standards:
MS-PS1-1 Develop models to describe the atomic composition of simple molecules and extended structures.
CCSS.ELA-LITERACY.RST.6-8.3 Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
CCSS.ELA-LITERACY.RST.6-8.7 Integrate quantitative or technical information expressed in words in a text with a version of that information expressed visually (e.g., in a flowchart, diagram, model, graph, or table).
Science and Engineering Practices:
In this lesson, students loot at similarities and differences between the structures of elements, molecules, compounds, and mixtures to develop a model that can predict or describe what type of matter a “mystery substance” is (SP2). In order to do this, students critically read scientific texts adapted for classroom use to obtain scientific information in order to describe these patterns in the structure of different types of matter (SP8).
Cross Cutting Concepts:
In identifying patterns in the structures of different types of matter, students can begin to gain an understanding that macroscopic patterns are related to the nature of microscopic and atomic-level structure (Patterns).
It is important to note that students in my school district have a chemistry and matter unit in their previous school year. At this point in my unit, I have reviewed the following skills with my students:
1. I can identify and create models that show the smallest component of an element is an atom.
2. I can describe how the elements within the periodic table are organized by similar properties.
Students have completed a few lessons and formative assessments so that I could gauge their level of understanding in these areas. Students have self-assessed themselves on their unit plan on a scale of 1 to 4 (4 being mastery). With each formative assessment and lesson, they have updated their level of learning as their level of mastery has improved. Notice the student below began at what she believed to be a 2 on Skill 1, but over the course of lessons adjusted her score to a 4.
In addition, students have self reported and graphed their scores on all formative assessments in these areas. Students graph their score (I score things on a scale of 1 to 4 (4 being mastery) and then write in at the bottom of the page the concepts or areas that they are still working towards mastery on. For example, the students below write things such as, "Most of the mass of an atom is in the nucleus." and "As you move from right to left on the Periodic Table, the atomic mass increases." These are concepts that these particular students struggled with the first time taught. This list will serve as resource for students to determine "focus areas" that they need extra help in or extra time studying as the unit progresses.
Thus, this lesson is the start of Skill 3 in the unit plan. Self assessment and self reporting of grades is an essential element of this unit and will continue in every lesson. If you are interested, I have included the notes I provide the students for Skill 1 and Skill 2 in the resources section. Each notes page includes a set of True/False Statements. I have included answer keys to those as well. Notice that if a student chooses "False", they must change the word(s) in the sentence that would make the statement true.
Begin the class by asking, “What are you going to learn today?”. Students should reply by stating that they are seeking the answer to the Essential Question listed on the Chemistry Unit Plan. The EQ for this unit is “How do particles combine to form new substances? What evidence can show how the physical and chemical properties of the substances change?”
Ask students to turn to their Chemistry Unit plan. Ask them to take a moment to silently break down Skill 3. Independently, have the students underline the key vocabulary and circle the key verbs in the sentence that tells the students what they have to be able to “do” with the vocabulary. In addition, have students rank themselves on a scale of 1 to 4 (4 being mastery), on where their level of learning is with this skill at this point. Emphasize that it is totally ok for them to be at a 1 or 2. This is the first day of the lesson, therefore, it is expected that students have not mastered the skill.
Skill 3: I can recognize how the particles in an element, molecule, compound, and mixture are different.
(At the end of this lesson, students re-assess their level of mastery. Notice that this student felt as if they began at a 3 and after this lesson were at a 4.)
After ranking themselves, ask the students to discuss as a class what they think Skill 3 is asking them to learn. Students usually say things like, “Be able to tell the difference between an element, molecule, compound, and mixture.” or “Look at a model of a molecule and say whether it is an element, molecule, compound, or mixture.”.
Explain that today, they will be creating models of elements, molecules, compounds, and mixtures using marshmallows and toothpicks. Explain that there are many patterns that occur with the structure of these types of matter and that their focus today is to try to identify these patterns.
At this point in the year we have worked towards independence in reading for understanding. We have implemented two strategies in particular to help us reach this goal: "Talking to the Text" and the "Ladder of Discourse". Talking to the text is a strategy in which students write their thinking on their paper while they read. We have discussed how effective readers do not just read the words on the page; they are constantly making connections and questioning the content. In conjunction with this strategy, we have worked on assessing the levels at which they are connecting to the text. The "Ladder of Discourse" includes four "rungs" including "Tweets" (basic text to self connections), "Huh's?" (words or concepts not understood), "Found It!" (using context clues to find answers/making connections to the science we are learning about in class), and "Discourse" (thinking beyond the text/thinking of an engineering design to develop or variables to test). Students have assessed their thinking as they read and organized these thoughts into these four categories. With these "rungs of the ladder" as goals, students have worked to push themselves to get to "Discourse".
Want some more information about these strategies and what my students have completed so far? Here are some lessons to look at:
I explain to the students that in this lesson they will be given the independence of following the procedure and finding the information from text required to complete the procedure on their own. I pump them up by citing all of the work they have completed to get to this point and that I am confident that if they continue to utilize the strategies we have worked on that I know they will be successful! I emphasize that they have to commit to following through with the strategies, however. When given independence, if they simply return to just "surface reading", their success at this task will diminish.
Provide students with the Marshmallow Molecules Directions and Student Worksheet. Explain to them that they will be following the procedure to complete the task of creating a poster that models the structures of elements, molecules, compounds, and mixtures. Explain that within the procedure it asks that the students read the Skill 3 Notes Page one section at a time. Emphasize that if these directions are skipped, the final product cannot be completed accurately. I tell them that as much as they want to rush and complete the poster; the reading and obtaining of information from the text is the most essential element of the process.
Purchase bags of small assorted colored marshmallows. The brand that is sold locally has bags including yellow, orange, green and pink marshmallows. Take time (or have students help) separate these bags into separate containers by color. I typically go through about 1.5 bags per section. In addition, you will need to provide toothpicks, glue and white 11 x 17 poster paper. I have students work in groups of 2-3. Groups any larger than that diminishes the impact of the activity for individual students.
In short, students divide their paper into four sections for "Elements", "Molecules", "Compounds", and "Mixtures". The procedure will explain and take them through exactly how to complete each section, including the shape and number of bonds for each molecule. Students read each section of the notes page as they follow along with the directions and complete each section of the poster. A couple student examples are included below. Following poster creation, students complete a worksheet asking them to identify structural patterns in each type of matter. A look at the connections students make is covered in depth in the next section.
Common Student Errors:
A student sample of the Marshmallow Molecule Student Worksheet is included in the resource section. The following video explains the patterns a student noticed about the structures of elements, molecules, compounds, and mixtures. The students also record the observations that this student makes on their lab sheet which is included in the resources section.
The second page of the student document also demonstrates whether the students have a conceptual understanding of what the particles in these various types of matter look like. In these questions, students use the pictures of the structures to aid them in determining if the matter is an element, molecule, compound, or mixture based on the structural patterns they observed when creating Marshmallow Molecules.
One major part of this unit that continues throughout each lesson is that students track their learning and self-report their grades. In my class, I score everything as a 1, 2, 3, or 4 (4 being mastery); thus, the y axis is labeled with these scores. However, you could place your own grading scale that represents your classroom. In addition, along the x axis, it is labeled "a, b, c, d, etc". In my gradebook, in order to organize all of my formative assessments in chronological order by skill, I have to include these; thus, I include this here. You might include assignment names or any other numbering system that would indicate time progression on the x axis.
After I assess the students' posters and lab sheet, students plot their score and then in the open area on the bottom, they add to their "Working Towards Mastery List". The "Working Towards Mastery List" is a place students write the concepts or topics that they have not yet mastered or need to study more in depth. It is a way for each individual student to organize their specific feedback. Come summative assessment time, students have a clear record of not only their growth, but of the specific concepts that they missed along the way that should be the focus of their studies.
The student below earned a "3" on this assignment which means that they have lots of knowledge about the skill but have just some minor misconceptions to clarify. This student has written their focus topics below. In this case, the student writes, "Mixtures are not all bonded (physically mixed)" and "Compounds all atoms are bonded".
Provide each table with a white board and a dry erase marker. If you do not have small white boards white paper and markers would work as well. I ask each person to write the words element, molecule, compound and mixture in the shape of its definition. For example, students during our waves unit wrote the word "absorption" before and after a sun shining on sun glasses. They explain that they wrote the "ABS" larger on the sun side of the glasses and the "orption" smaller on the other side because some of the rays were absorbed by the glasses. (Here are a couple of other lessons that use Shape Vocabulary: Heat Transfer, Frequency, Wavelength, and Amplitude, The Amazing Ivory Soap Bar, and Analog vs. Digital Signals)
I tell the students that they can add small pictures, but the way that the word is written should be in a shape that shows meaning. In addition, I emphasize that their drawings of compound and molecules should demonstrate the difference between the two. (Notice in the examples below, students connect different letters with bonds for compound, but connect the same letters with bonds for molecules to demonstrate that a compound must have at least two different elements but molecules could be more than one of the same element bonded together.)
After completing their Shape Vocabulary, have each group explain to another group the decisions they made in their shapes and how what they wrote demonstrates the definition of each word.
In the video below, a student describes their decisions for their shape vocabulary. The student in the video notes that a pure element would not have bonds. In addition, she drew atoms of the same color connected by the word "molecule" as the bonds while she drew different colored atoms connected by the word "compound" for bonds. Last, she states that she wrote "mixture" over and over because these substances are mixed but are not connected because they can be separated by physical means.