Setting Up the Sticky Tape Lab and Making Sense of the Results
The sticky tape experiment in Unit 6 is one of those labs that looks simple on paper but generates a lot of confusion when students actually try to work through it. You start with two strips of ordinary adhesive tape, pull them apart from a surface, bring them close together, and observe whether they attract or repel. That's the whole procedure. The complication comes afterward, when you're supposed to figure out what just happened and translate it into an answer key. Most people struggle with this because the lab is trying to demonstrate electrostatic charging through contact and separation, but the instructions often leave out the details that actually matter for getting consistent results. I've seen this lab run dozens of times in different classrooms, and the single biggest source of error isn't the physics. It's the tape itself.
The Sticky Truth Unpeeling The Mystery Of Chemistry Unit 6 Sticky Tape Post Lab Answer Key
Here's how the experiment actually works and what you should expect when you fill out the post-lab questions. You take one strip of tape and press it firmly onto a smooth surface like a lab table or a piece of glass. That's your base strip. Then you take a second strip, press it on top of the first one, and smooth it down hard. When you pull both strips off the surface together, they pick up charge. Separate them quickly. Now you have two charged strips. When you bring the two strips close to each other, they repel. This is because both strips acquired the same type of charge through the same process. The tape and the surface exchange electrons during contact, and when you separate them, each strip carries away a similar net charge. Like charges repel. That's your core observation and the foundation for almost every question in the post-lab.
Next you do the variation where you keep one strip fixed to the table as a base and peel a second strip off it. When you bring that peeled strip near the already-stripped tape, they attract. This is the part that trips people up the most. The strip that was peeled off has a different charge sign than the strip that stayed behind, because the electron transfer happened in opposite directions relative to each piece. The answer key questions typically ask you to identify which strip is positive and which is negative, explain the charging mechanism, and relate the observations to the atomic model. The standard explanation goes like this: tape pulled from a surface gains or loses electrons depending on the materials involved. In the typical classroom setup with ordinary Cellophane or masking tape on a laminated lab surface, the top strip usually loses electrons and becomes positively charged while the bottom strip gains those electrons and becomes negatively charged. But this isn't universal. It depends on the specific tape formulation and the surface material. If your school uses a different brand, the polarity can flip. I ran into this exact problem a few years back when my classroom supply box had switched to a cheaper generic tape without anyone noticing. Every group got the opposite charge results from the textbook answer key. Students were convinced they were doing the lab wrong. The workaround was straightforward: I had them use a third test strip and compare all three combinations before drawing conclusions. When two strips repelled each other, you knew they had the same charge regardless of whether that charge was positive or negative. The relative behavior matters more for the lab objectives than identifying the absolute sign.
Get the Full Details
The post-lab questions usually include a section on why the tape behaves this way at the atomic level. You need to reference electrons as the mobile charge carriers, explain that protons stay locked in the nucleus and don't move during this process, and describe how the triboelectric effect creates charge separation through contact and separation. A complete answer should mention that no new charge is created. Charge is only transferred from one material to another, and the total charge remains conserved. Another common question asks students to predict what happens when you bring a charged tape strip near a neutral object like a stream of water from a faucet. The tape attracts the water because the charged tape induces a polarization in the water molecules. The positive and negative ends of the polar water molecules reorient toward the tape, creating an attractive force even though the water as a whole is neutral. This is induction, and it's distinct from the charging by contact you observed with the tape strips themselves. Students regularly conflate the two mechanisms, so make sure your answer clearly distinguishes between charging by contact and charging by induction. If your answer key includes a quantitative component, it might ask you to calculate the number of excess electrons on a strip given a measured charge value. Use the elementary charge value of 1.60 times ten to the negative fourteenth coulombs per electron. Divide the total charge by this value and you get the number of electrons. Be careful with significant figures. The charge measurements from these labs are rarely precise, and reporting ten significant figures won't make your answer any more correct.
There are a few edge cases worth knowing about. Humidity is the main one. On a day when the relative humidity is above sixty percent, the charges leak off the tape much faster because water molecules in the air provide a conductive path. You'll notice the tape stops repelling after a minute or two on a humid day. If your lab results look inconsistent, check the weather report before concluding that your procedure was flawed. Dust and surface contamination on the tape or the lab bench also interfere with consistent charging. Wipe the surface with alcohol if you can, and use fresh tape from a new roll rather than one that's been sitting open for weeks. The answer key will likely have a discussion question about real-world applications. Common acceptable answers involve lightning, photocopiers, electrostatic precipitators in industrial air cleaners, and the way dust clings to screens. None of those require a long explanation. One clear sentence connecting the lab observation to the application is usually sufficient. One thing the standard answer key rarely addresses adequately is the role of the adhesive itself. The sticky side of the tape participates in the charge transfer, and different adhesives have different positions on the triboelectric series. If you're doing this lab with multiple tape types for a comparison section, expect variation in both the strength and sometimes the sign of the charge. That's normal and not a mistake. A good post-lab discussion acknowledges this variability rather than pretending every strip behaves identically.
