Making personalized stirring rods

Creating personalized stirring rods 

How great is it for students to get to experience working in the lab, all while creating a useful piece of lab equipment that can be used for the remainder of the school year? Within the first month of school, my 10th grade chemistry students perform a series of lab experiences. They practice techniques such as heating a test tube, reading a thermometer to the proper number of digits and — always a student favorite — making their own glass stir rod. 

The rods are made by sealing the ends of glass tubing using a Bunsen burner. Into the stirring rods, students insert their names and class; many students add extra decorations, such as glitter, colored wire, pipe cleaner or small beads. 

Glass tube cutting tool¹

The glass tubing is ordered from Flinn Scientific — glass tubing, soft glass, 24” lengths. Soft glass must be used, not borosilicate glass. I order tubes with a 6 mm (outer diameter)/4 mm (inner diameter). A larger size would also work, but anything smaller and the opening would be too small to get a label inside. Each 24" piece of glass tubing can make two stirring rods, so a package of 10 is enough for 20 students. We begin with a demonstration on how to cut a piece of glass tubing with a special cutting tool or etching with a triangular file. Both work well, and the glass breaks very easily so only a fine score line is necessary. The tube is snapped off, away from one's body. Students do their own cutting. Flinn has a great video on how to cut glass tubing as well as polishing and bending it.²  

The tube ends are sealed just by gently rolling it in the Bunsen burner flame. The flame will be orange due to the sodium in the glass. I instruct students to help each other be sure the end is sealed before removing it from the flame. Once the first end is closed, students are required to add their name and class period — a little piece of paper will work. After students have finished “inserting their desired material”, the second end is sealed. 

There is safety to consider and I repeatedly remind students that hot glass looks just like cold glass!!! Be very careful and wait at least 15 minutes before touching the end that was in the fire. As with any lab involving an open flame, hair is tied back and goggles are mandatory — and definitely try this on your own to work on your technique. 

Student measuring and marking the glass tube to cut.

Above and below: Complete concentration while carefully rolling the end of the glass tube at a 45 degree angle in the tip of the blue cone of the Bunsen burner flame.

Personalized stirring rods ready for use in the experiments to come.

A few additional tips that I offer to students include:

• Do not take glass in and out of the flame — doing so makes it much more difficult to close the glass tubing.
• Use an “efficient flame” on your burner (strong roaring flame with an inner and outer blue cone).
• Place the very tip of the glass tubing in the very top of inner blue cone at a 45 degree angle. 
• When closing the second end of the glass rod leave 1½ - 2” clear of anything flammable (pipe cleaner, glitter, paper, etc). Hint: A Q-tip works well to clean the inside before placing it in the flame to close.
• It takes 1 to 2 minutes of “rolling the end” in the efficient flame to completely seal one end. 

Following is the grading rubric I use.

Stirring Rod Evaluation

3 = Perfect; 2 = Good; 1 = OK; 0 = Not complete

This lab idea and rubric was shared with me 15 years ago during my student teaching experience at Ludington High School by now retired teacher Kathy Winczewski. Several years ago I suggested this activity to Erika Fatura, Pentwater Public School District, Pentwater MI. Want to know if this activity is worth it? 

Here is Erika’s response:

At first, I was a little skeptical as I was concerned with the safety aspects of this lab. After trying it out and getting comfortable with it myself, I realized we should be providing lab opportunities where it is important to carefully follow all of the instructions and safety guidelines. Students are motivated to closely follow the instructions, not only for their safety, but they really want to get a nice looking stirring rod. I love the idea of allowing the students to decorate them and add their own personal touches! Here is what two of my students said: 

It was not only fun to make the stirring rods, but throughout the year it was exciting to be able to use something we made in our labs." — Jenny

I was really afraid of the lab at first, but it ended up being really fun!" — Iain

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References

1. Photo of glass tubing cutter from Flinn Scientific catalog www.flinnsci.com/glass-tubing-cutter/ap5418/

2. www.flinnsci.com/how-to-cut-fire-polish-bend-glass-tubing/vht0036 

Editor’s note: One proofreader suggested having students calculate whether the stirring rod would float in water.