This lesson contains an activity that’s derived and modified from the Virginia Department of Education: Science Enhanced Scope and Sequence – Chemistry.
This is the second lesson of the unit where students begin to see there are different ways to measure and quantify objects. This lesson has student measure a quantity of unpopped popcorn and use their data to develop an imaginary unit that will be similar to a dozen=12, a gross=144 or a mole=6.02 x 1023 atoms.
If students approach the mole both conceptually through inquiry, and mathematically, they will be better adapted to comprehend the mole through a variety of chemistry problems. The idea is to develop a solid conceptual and analytical understanding of the mole.
Previous knowledge and skills needed for this activity
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 develop an understanding of the mole as a basic counting unit in chemistry used to keep track of the amount of atoms present in matter.
Science and Engineering Practices (SP)
HS-PS1-7 is one of the few high school Performance Expectations with the primary focus on the use of mathematics to describe a concept. Mathematical and computational thinking at the 9–12 level builds on K–8 and progresses using algebraic thinking and analysis. Through their computational thinking, students will develop a way of counting various material that can be used as a parallel to help understand the mole as counting unit for the atom.
The first 5 minutes of class is a think pair share (TPS). For the last several days my students have noticed a 5 gallon jug of golf balls on my desk and have been asking what I am doing with the jug. I have been telling them nothing which has built curiosity. As mentioned in the introduction, students will be using the popcorn during a counting activity.
To start the TPS I ask students to write down as many questions or observations about the container of golf balls. This should only take a minute or two. I then pair up kids with the person next to them, or if they’re 3 at a table they can work as a threesome. While in their groups I instruct them to share their thoughts with their partner(s) and come up with the question or thought that can be shared with the class. Some possible student thoughts or questions:
The main question(s) I am looking for, which are almost always asked, are question 2 and 4. If they are not asked I will ask if anyone is curious about how many kernels.
I then give them a minute to think and talk with their partners about ways to count the balls. This gets the conversation going about how to calculate large quantities of objects. After a minute or two of class discussion about possible ways to determine the number of balls the class should come to the determination that weighing is a better option than counting. This is a good segue into the activity.
In this activity students will determine the relationship between mass of a popcorn kernel and the number of kernels in that sample. Students will give the relationship a name called a popcorn counting unit (PCU), which can later be used as a comparison to the mole. After practicing calculations using the PCU, students will use the counting with other substances (beans) to determine their mass based on the counting unit.
While we are having our group discussion I handed out the activity and a scale to each table. Students will work with their TPS partner(s) on the activity and have to share the scale with the other group at their table.
Since this is a guided-inquiry activity I only provide students with a little instruction. The majority of instruction will come from the activity handout. Prior to this activity my students have had sufficient practice with proper weighing technique, factor labeling, scientific notation and a brief introduction of the mole and Avogadro's number.
Guided Instruction (prior to activity)
After providing the brief guided instruction, students can begin to work on Part 1 and 2. While they are working on this I circulate to each of the groups to ensure they are following the procedures correctly.
As students move through part 1 they may need help with calculations, since some students struggle with units (such as PCU) that are not familiar to them. This is fine because right now they are developing an understanding of how there are different ways to measure.
As the activity goes on I remind students to put question 8 in the class data table and move on to part 2. Some groups may need help with part 2 because it requires them to apply some of the information from part 1 to answer the questions.
Since students complete parts 1-3 at different paces the Explain (white board) portion of the lesson will be conducted the following day. I have included an explanation in this lesson to guide you into the next lesson. It is important that students are aware that they will be responsible for this portion of the activity on day, so I will briefly cover this with 10 minutes left in the period. This also provides time for students to reflect on the lesson and clean-up.
When all groups have completed part 1, 2 and 3, the activity is concluded with groups presenting what they have learned about counting units (competed during Introduction of the Mole-Day 2). The goal of the activity is for students to develop an understanding of a counting unit and relative masses as a foundation for understanding the mole. At this point in the lesson the have been introduced to the mole, but have a very limited understanding of its relationship to Avogadro’s number as a quantity. This activity is the first of several that slowly build an understanding of the mole, molar mass, # of particles in a substance and the conservation of mass in chemical reactions.
With 10 minutes left each group will have 1-2 minute to discuss what they learned. Each group will take their white board to the front of the class and share with the class. If time permits, other groups will have the chance to make comments. Since there are 10-14 groups, comments will be very brief.
The purpose of the presentation is for me to get a quick, informal assessment of what each group learned from the activity. In addition it provides students with a deeper explanation of what they explored. I believe the process of students seeing and learning what other students have learned is a valuable learning tool that is an important part of inquiry. This type of learning can be used to build a more authentic understanding of difficult content, such as the mole.