In this lesson students are introduced to the idea of the Mole and Molar Mass.
I introduce these concepts in relationship to the Periodic Table and Atomic Mass values on the Periodic Table. This is a concept that builds on Dimensional Analysis which I introduced in Unit 1 Lesson 6.
Students are performing two lab activities, notes, whiteboards, and practice questions during the lesson.
This lesson aligns with three aspects of the Next Generation Science Standards:
In this lesson there are several sets of materials needed:
To engage students in the lesson and to review Dimensional Analysis from the previous unit I have students perform a Dimensional Analysis Problem.
When students perform this problem I encourage them to try it on their own first and if they are stuck to go back and look over their notes from the previous unit.
I then have them work with their table partners to check their work I go over the answer making sure to highlight the plug and chug technique where they underline what they know, circle what they want, use equivalence statements to get their answer.
One example of the answer is found at the top of this student work example.
I have found that students have a very difficult time understanding the concept of the mole so I decided to have them start to understand the idea in this exploration activity.
In this activity students weigh out one mole of three different elements (Sulfur, Carbon, and Aluminum).
Before the lab I weigh out the molar mass of each substance into a plastic petri dish container with the mass of the container written on top of each.
The instructions for the lab are on the 2nd and 3rd slide of the Power Point and on the student notes graphic organizer. Students also fill in the information and answer the questions on the first page of the graphic organizer.
In the lab students find the mass of the sample in the container, subtract the mass of the container, and write down the mass of the sample itself. They then write down information about the element from the periodic table including the atomic symbol, number and mass. This image shows students finding the mass of the containers.
Some students are not sure how to find the mass of the sample itself in the third column of the activity so as I walk around I tell them, "So if you found the mass of the same and container, and then the container itself, how can you figure out the mass of the sample itself"?
Afterwards they answer two questions to lead them to the idea that a mole equals the atomic mass of the substances and that to determine what to weight out I looked at the atomic mass on the periodic table.
This student paper shows one student's work for the lab and answers to the questions.
I begin with going over atomic mass and relating it to the activity that students performed in the Explore section.
I then introduce the idea of the Mole. After a quick introduction that brings students through the first page of the notes I have students watch a TedEd movie "How Big is the Mole". This is a quick 4.5 minute movie that helps students to see just how small an atom is and just how many particles are in a mole. While watching the video I instruct students to simply pay attention because the mole is a tricky concept.
After the video I continue to introduce students to the Mole and then teach them how to perform unit conversions from the mole to atoms, and then atoms to moles. As I teach each type of conversion I lead students through two example problems. As I do the problems I reinforce that they use the proper dimensional analysis Plug and Chug technique.
In this section I perform two activities with students to allow them to practice molar conversions.
1. I first have students do whiteboards with partners. I use the mole_white_boards Power Point and give students one problem at a time. See the reflection in Unit 1 lesson 6 regarding Partner Appointments for further details.
2. After Whiteboards I have students do a Compounds of Chalk Lab.
The most common mistake that students make are: