I start the lesson by displaying a variety of common compounds and elements, such as water (H2O), sugar (C6H12O6), salt (NaCl), carbon (charcoal), helium (in a balloon), iron (nail), copper (wire or penny), and aluminum (foil). I play an altered version of "Guess My Rule", having the students to pair up and discuss how these samples are similar and different, as well as to write down a few ideas as to the "rule" or criteria I used to group them. (For more information on "Guess My Rule", please see my reflection.)
Once the student pairs have had a chance to brainstorm, I physically separate the examples into two groups based on whether they are made of compound molecules or are purely one type of element, but I don’t explain my reasoning for creating these two categories. Again, I ask the students to pair up (this time with a different partner) and to decide my criteria for classifying the items. After allowing 2-3 minutes to discuss and calling on volunteers to share their ides, I tell the students that we will come back to these two groups later and discuss what my reasoning criteria might have been for this grouping.
Next, I explain to the students that in order to study chemistry, we first need to know about matter and where all of it comes from. In order to do this, the students will watch a Bill Nye video on atoms. While watching, the students will be responsible for completing a worksheet, answering questions as the movie progresses.
I pass out the worksheet and have students preview the questions first, attempting to answer any they think they may already know and getting an idea of what to look for as they watch the video. They should revise any questions they answer now if they learn something in the video that contradicts their original response.
I love Bill Nye's videos because - even though they're slightly outdated - they are engaging and a little silly, but also explain material in a way that is understandable for a wide variety of ages and is quite accurate. I think they combine just the right amount of science and fun!
For this lesson, and the others that follow, a lot of new vocabulary will be introduced. Mastery of this vocabulary will be needed in order to work through the lessons successfully. For some information on how to begin teaching vocabulary in the classroom, please watch my video below:
After watching the video and reviewing the answers on the worksheet, I ask the students, “What do we know about matter?” (Matter is made up of tiny particles called atoms). I explain that all molecules are simply two or more atoms bonded together. If a molecule is made of many the same kind of atom, it is called an element. I ask the students how many have heard of the Periodic Table of Elements, explaining that the last word, elements, refer to the molecules that are made of many of the same type of atom. I play the They Might Be Giants video to provide more information about elements, including examples:
Students will often identify elements they have heard of while watching, and will usually call out the names of elements that are familiar. I allow them to do this, as it encourages them to make connections to their own experiences and prior knowledge. However, I do stop them if their comments become irrelevant or distracting to others.
Next, I explain that sometimes, different atoms also combine to create new substances. Molecules made up of more than one kind of atom are called compounds. I tell the students they they will get a chance to build models of both elements and compounds in the next activity. I pass out the “Making Molecules” worksheet and read the background section aloud as the students read along silently.
The students work their way through the lab, building models of several molecules. As they work, I circulate throughout the room, checking the accuracy of their work and asking them clarifying questions to assess their knowledge, such as:
These questions can also be asked to the class, to spark discourse, after the lab is completed.
If time permits, I also like to show the Periodic Table Crash Course video. It is a fast-paced video about the Periodic Table of Elements and the purpose behind the arrangement of elements. While some of it is a little beyond what we are currently studying, it is a great introduction to concepts and terminology we will study in the near future.
I return to the items displayed in the front of the classroom and, again, ask the students to consider how I grouped them into two distinct categories. My goal is for the students to realize that they are grouped according to their molecular makeup - one group is made up of pure elements (all of the same molecules), while the other is made up of a compound of different molecules. Both, however, may contain different atoms, depending on which molecules were used in each substance.
As a final assessment of the students' understanding of molecular compounds, I have them get a blank piece of paper and access the website, Chemicals In The Home. Once they access the site, they select three different household chemicals from the list and draw models of each, listing the common and scientific names of the compound and the atoms that combine to form each one. I allow the students to use the dynamic Periodic Table to look up names of unfamiliar elements as they work.