Percent Composition Cryptex Puzzle

prusaprinters

<p>This is a puzzle designed to be used with a General Chemistry course (either high school or college) that reinforces the learning goal of determining the empirical formula of a compound using the percent composition of the elements in that compound.</p> <h3>Print instructions</h3><p>There are eight printed pieces in this puzzle:<br/> 1 base<br/> 1 key (has percent composition on one face of the key). Also including a blank key if the end user would like to remix it for a different compound.<br/> 6 register cylinders<br/> 1 brace (holds the register cylinders onto the base)</p> <p>The user will need to supply the following hardware parts:<br/> 3x M3 x 8 mm socket head screws<br/> 3x M3 square nuts</p> <p>Recommended settings: Use PLA, PETG, or ABS with a layer height of 0.2 mm. I used PLA with a rectilinear infill of 15%, but this could probably be adjusted for speed or strength.</p> <p>Printing details: The base and register cylinders can be printed without a brim directly on a smooth PEI sheet. The key can also be printed directly on the smooth PEI sheet, but will need to include "support everywhere" in your slicer settings. The key will need post processing to remove the support material and smooth out any rough edges of the key. You may also find it necessary to gently sand the contact edges of the brace and cylinder registers to allow for the best fit.</p> <p>The recommended color coding for the subscripts of the different elements (C=black, H=white, N=blue, O=red) come from the CPK coloring convention (<a href="https://en.wikipedia.org/wiki/CPK_coloring">https://en.wikipedia.org/wiki/CPK_coloring</a>) most often used in molecular modeling. For the key included (pepstatin, C34H63N5O9) in this kit, you will need to print out the following register cylinders in the indicated color:<br/> Black (for carbon), cylinders 3 and 4<br/> White (for hydrogen), cylinders 6 and 3<br/> Blue (for nitrogen), cylinder 5<br/> Red (for oxygen), cylinder 9</p> <p>When printing the brace, you will need to insert 3 M3 square nuts into the model partway into the print. If using PrusaSlicer, simply include a "color change" at the 35th layer (at 7.00 mm). When the printer prompts you to change the color, insert the square nuts so that they are completely flush and then resume the print using the same color.</p> <p>How to solve: Search Google for "percent composition to empirical formula" for many different tutorials (example, <a href="https://www.chemteam.info/Mole/Emp-formula-given-percent-comp.html">https://www.chemteam.info/Mole/Emp-formula-given-percent-comp.html</a>) on the subject. However, I will point out a few important details. I purposely picked very large molecules to make each of my puzzles unique for each student. As a consequence, I recommend using atomic masses out to the hundredths place when doing your calculations. For these puzzles, I used 12.01 g/mol for carbon, 1.01 g/mol for hydrogen, 14.01 g/mol for nitrogen, and 16.00 g/mol for oxygen. If you round your atomic masses to the nearest whole number, you are likely to get an error in your calculation. Best of luck.</p>