Chemistry Unit 6 Sticky Tape Post Lab Answer Key

Understanding the Sticky Tape Electrostatics Lab

The Sticky Tape lab in most chemistry curriculums is an exercise in charge quantization and electrostatic interactions using adhesive tape as a controlled way to generate and measure static charge. It typically appears in Unit 6 of a standard high school chemistry course, though the exact numbering varies by textbook and school district. Students peel layers of tape off a surface and from each other, observe attraction and repulsion, and use the results to build a two-charge model of electrostatics. I've supervised this lab in multiple iterations across different classes, and the main problem everyone hits is that the results are highly dependent on ambient humidity and the type of tape being used. If the relative humidity is above 60 percent, the tape doesn't hold enough charge to produce clean observations. I once spent an entire class period watching students get confused because nothing seemed to attract or repel. The fix was simple: switch to heavier packing tape instead of the thin clear tape, and run the experiment in a room where the air conditioning has been running for at least an hour to dry things out.

Chemistry Unit 6 Sticky Tape Post Lab Answer Key

Below is a breakdown of the standard questions that appear in the post-lab assignment and what the expected answers should be based on the two-charge model taught in this unit. This isn't a shortcut to skip the work. You need to have actually performed the lab to make sense of the results, but this will help you check your reasoning. Question 1: What types of charge did you observe? The answer should identify two types: what most curricula label as "upper tape" (U-tape) and "lower tape" (L-tape). These are conventionally called positive and negative, but the specific assignment of which is which depends on your textbook. The key conceptual point is that U-tapes repel each other, L-tapes repel each other, and U and L tapes attract each other. If your data shows something different, your technique was likely flawed rather than your conclusion.

Question 2: How do like charges and opposite charges interact? Like charges repel. Opposite charges attract. This is the fundamental electrostatic principle the lab demonstrates. The tape experiment makes it concrete because students can physically see and feel the force. The magnitude of the force follows Coulomb's law, though at this level you usually just need to state the qualitative relationship rather than calculate it. Question 3: When you bring a charged tape near a neutral object, what happens and why?

The charged tape induces a polarization in the neutral object. Charges within the neutral material redistribute slightly, creating a region of opposite charge closer to the tape and a region of like charge farther away. Since the opposite charge is closer, the attractive force dominates and the neutral object is attracted to the tape. This is called electrostatic induction and it happens with any conductor or dielectric, not just tape. Question 4: What happens when you touch a charged tape to a grounded conductor? The charge drains away through the ground connection. For students using their finger as the ground, electrons flow between the tape and the finger until the net charge is neutralized. The tape then becomes electrically neutral and no longer attracts or repels other objects. This is a standard discharge procedure and it confirms that the tape's prior behavior was due to accumulated charge, not some permanent property of the adhesive.

Question 5: Explain why the L-tape and U-tape have opposite charges based on your observations. When you peel the L-tape from the table surface, electrons transfer between the adhesive and the substrate. When you then peel the U-tape away from the L-tape, a second charge separation occurs. The two peeling events produce opposite net charges because the direction of electron transfer reverses depending on which material loses electrons and which gains them. The triboelectric series determines the direction, though most introductory courses don't require students to memorize the full series. What matters is that the experimental observation of mutual repulsion between L-tapes and mutual attraction between L and U tapes confirms they carry opposite charges. Question 6: Calculate the number of excess electrons if a tape carries a charge of approximately 10^-8 coulombs.

Using the elementary charge of 1.602 × 10^-19 coulombs per electron, you divide the total charge by that value. That gives roughly 6.24 × 10^10 excess electrons. Write the calculation clearly showing the formula q = n × e rearranged to n = q/e. Most graders want to see the setup even if the arithmetic has a rounding difference. Here's something that consistently trips students up: the amount of charge on a single piece of tape is incredibly small in absolute terms, but the forces are easy to observe because the masses involved are also tiny. A few nanograms of tape moving a millimeter is very noticeable. That's why this lab works so well as an introductory demonstration even though the underlying physics is the same as what governs lightning strikes. Another counter-intuitive point that beginners miss: you can actually increase the charge on a tape by repeating the peel more slowly and more completely. Fast peeling doesn't allow enough time for charge transfer to occur at the interface. I've seen students get weak results and conclude the tape was "bad" when really they just peeled too quickly. A slow, deliberate peel across the full length of the tape produces the strongest and most reproducible charges.

There are real limitations to this lab that teachers sometimes gloss over. The two-charge model is a simplification. In reality, different tape brands and even different batches from the same brand can produce different charge magnitudes and occasionally different polarity assignments depending on the adhesives used. Some schools report that their U-tapes act like negatives while others act like positives, and both are technically correct within the framework because the labels are arbitrary conventions. The important thing is internal consistency within your own experiment, not matching someone else's label assignment. Humidity is the biggest practical bottleneck. Above 65 percent relative humidity, the results become unreliable and students spend more time troubleshooting than learning. In very dry conditions below 30 percent, charges can build up so strongly that tapes stick to everything including the ceiling, which is annoying but not dangerous. The optimal range is 35 to 50 percent relative humidity. If your lab space can't be controlled, running the experiment on a day with stable weather conditions rather than during a storm front passing through makes a measurable difference in data quality. For students who want to download or reference the official answer key, most schools post theirs through their learning management system. Check Canvas, Google Classroom, or whatever platform your teacher uses. Some districts also share them through their public curriculum websites. If you can't find yours, the content above covers the standard expected answers. What matters more than having the exact wording is that your lab report shows you understand the charge model, can interpret your own data correctly, and can explain the induction and polarization concepts without memorizing phrases.

The lab itself takes about 45 minutes to complete including the actual peeling and testing portion. The post-lab write-up usually takes another 20 to 30 minutes if you're working carefully and showing your calculations. Budget your time accordingly instead of rushing through at the last minute, because the charge calculations and the qualitative reasoning questions are where most points are lost.