Lesson 2 of 9
Objective: Students will be able to differentiate between ionic and covalent compounds by performing eight different tests.
In this lesson students have the opportunity to explore the characteristics of substances ionic and covalent bonds through eight different stations. In particular they learn about conductivity, crystal structure, ease of burning, components, brittleness, energy of bond formation, melting points, and electronegativity differences between these two types of substances.
- This lesson aligns with NGSS Performance Expectation: HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
- This lesson aligns with NGSS Science and Engineering Practice 3: Planning and Carrying out Investigations because students are performing a lab.
- This lesson also aligns with NGSS Science and Engineering Practices 6: Constructing Explanations because students are coming up with a claim about ionic vs. covalent and using evidence to support their claims.
Within this lesson there are many resources needed for the lab. This is a list of supplies for each station:
- Two conductivity testers, one beaker with water and salt labeled Ionic, a second beaker with distilled water and sugar labeled Covalent.
- A microscope (I use a digital microscope with a laptop so all students in the group can see the same image together), microscope slides or mini petri dishes with covalent substances (I use powdered sugar labeled Covalent #1 and corn starch labeled Covalent #2) and ionic substance (I use sodium chloride labeled Ionic #1 and copper chloride labeled Ionic #2).
- A Bunsen Burner, a sparker, two labeled nichrome loop wires (one ionic and one covalent), a dish of water, a container with salt labeled Ionic, and a container with sugar labeled Covalent.
- A periodic table with the metals, non-metals, and metalloids labeled, and a list of ionic and covalent covalent compounds. The first page of this pdf has the paper I use.
- Two mortar and pestles, a container with salt labeled Ionic, and container with corn starch labeled Covalent, a waste container labeled Ionic, and a waster container labeled Covalent.
- A Bunsen Burner, a sparker, magnesium ribbon in a container, carbon (charcoal) in a container, two metal forceps, two metal tongs, a waste container labeled Ionic, and a waste container labeled Covalent.
- A table with melting points for common Ionic substance and common Covalent substances. The second page of this pdf has the paper I use.
- A periodic table with electronegativity values and a list of Ionic and Covalent substances. The third page of this pdf has the paper I use.
To engage students in the lesson I begin by passing out the Lab Paper and read through the objective and procedures with students.
- As I do this I make sure to stress that in the last unit we focused on individual atoms and in this unit we will learn about what happens when atoms combine.
After reviewing the general objective and procedures for the lab I explain to students that they will be writing a claim and evidence for the claim at each station.
- I first review the definitions of claim and evidence
- I then go over the sentence starters provided on the lab.
- I have found that although students are often familiar with claim and evidence from English class and the Common Core curriculum that they still need a refresher.
- I make sure to stress to students that the claim should be about the particular station that they are working at and the evidence should come from the procedure that that they performed.
Once I have gone over the general idea of the lab I take a few minutes and just quickly talk about each of the 8 stations.
- I go over safety for each station including not touching the conductivity testers, wearing goggles for the stations with the Bunsen Burners and being very careful with my digital microscope.
- I also quickly point out what the claim should be about for each station. For example for station #1 I say, "Your claim should be about ionic vs. covalent and conducting electricity with your evidence having to do with what happened with the conductivity tester."
Finally I split students into cooperative groups by passing out cards. I tell students that they should be rotating roles at each station. For more information about my cooperative groups see my reflection from unit 1.
In this portion of the lesson students actually do the lab on the Lab Paper.
These are pictures from each station showing what they look like:
Because I did this lab on a short day I only had about 40 minutes for students to do the lab. Therefore I gave them 4 minutes per station which I timed using my Timer Tools countdown timer. To see how I use Timer Tools see this reflection from unit 1.
For the first set of stations I give students an extra minute so that I have time to go through and talk with each group to ensure that they are coming up with a claim concerning their station and evidence to support the claim. I also make sure that their claim has to do with ionic vs. covalent compounds.
Also, as students are working I continuously ask them:
- "What are you testing at this station?"
- "What is your claim?"
- "What evidence do you have to support this claim?"
- This video shows how I do this in my classroom.
As students are completing the lab I have them start the conclusion and complete for homework.
When students complete their labs I have them turn their labs in and grade using a rubric.
The rubric ensures that they are writing down observations, claim, and evidence for each station. Additionally, it gives them points for their conclusion.
Here is an example of a graded lab with the rubric.
- This student did a great job of writing claims and evidence for the claim at each station.
- She made use of the sentence starters provided in the lab introduction.
- For station #3 she did not refer to burning, but to chemical change but I still gave her full credit.
- For station #7 she did not refer to high versus low melting points so I took 1 point off.
- For the conclusion she did a good job of pointing out that ionic and covalent are different and gave examples of how they are different. Also for her source of error she chose to refer to the conductivity tester which worked for this lab. She could have been more specific but I still gave her full credit.