Love learning how the universe works. Red arrows represent the constant motion of the charges within the molecule that cause the momentary dipole. Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. The default activity then dives in to why octane has a greater surface tension than pentane by relating students’ macroscopic observations to particle-based models (figure 3). By turning the screw in the micrometer, the original 1 mm gap starts to widen, and the liquid begins to stretch (see figure 1). Students who demonstrate understanding can plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles. The default activity then dives in to why octane has a greater surface tension than pentane by relating students’ macroscopic observations to particle-based models (… The concept of London dispersion forces is introduced by focusing on the momentary dipoles that appear within each molecule and the effect these forces have on surrounding molecules to account for the differences in attraction. Eventually, the gap becomes too large and the stretched out liquid snaps back. Emphasis is on understanding the strengths of forces between particles, not on naming specific intermolecular forces (such as dipole-dipole). Blue arrows communicate how oppositely charged parts of each molecule are attracted to one another. Based on this, students now have evidence to support the idea that the -OH group must be playing some kind of significant role and their original claim that longer alkanes result in greater attraction is now in question and must be modified in some way. Though demonstrating the presence of these forces in a simple and explicit manner can easily be done, I wanted to change how I introduced IMFs a bit this year by focusing on a more data-to-concepts approach. Considering the foundational role intermolecular forces (IMFs) have when trying to explain and understand chemical phenomena, it is likely that this topic is addressed, to various degrees, in the classrooms of many chemistry teachers. Do much potential. Next, particle models of two alkanes (pentane and hexane) and an alcohol (pentanol) are introduced (see figure 4). Always trying to better my profession. Figure 5: Model displaying pentanol and the difference in the magnitude of the dipole that forms on the OH group compared to the momentary dipoles between carbon and hydrogen. Chemical reactions, including rates of reactions and energy changes, can be understood by students at this level in terms of the collisions of molecules and the rearrangements of atoms. Students are able to use the periodic table as a tool to explain and predict the properties of elements. Like any good scientific investigation, the evidence drove the understanding and I will certainly repeat this activity again in the future. Surface tension of pentane Book Title Supplement to IV/16 In Data extract from Landolt-Börnstein IV/24: Surface Tension of Pure Liquids and Binary Liquid Mixtures Book DOI 10.1007/978-3-540-75508-1 Chapter DOI 10.1007/978-3-540-75508-1_103 We also measured serum levels of the antioxidants tocopherol, retinol, lycopene, beta carotene, ascorbate and zinc. Again, this is what I like about this activity—data-to-concepts. Is this connected to one of the presentations from last summer? The surface tension of n-pentane, n-heptane and some of their mixtures were measured at 91.3 kPa and T = (283.15 to 323.15) K by the maximum bubble pressure method. Using a micrometer, a device used to measure small distances or thicknesses between its two faces, a small amount of a certain liquid is placed between a 1 mm gap. Figure 2: GIF of two liquids in Pivot Interactives activity (Image used with permission from Pivot Interactives). Using this expanded knowledge of chemical reactions, students are able to explain important biological and geophysical phenomena. Ben, I love this! Eventually, students are aware that the longer the alkane is, the greater the attraction will be. Use a model to predict the relationships between systems or between components of a system. Students are also able to apply an understanding of the process of optimization in engineering design to chemical reaction systems. Modeling in 9–12 builds on K–8 and progresses to using, synthesizing, and developing models to predict and show relationships among variables between systems and their components in the natural and designed worlds. Our readers are most interested in finding activities linked to NGSS, support for teaching AP chemistry, tips to make their labs and classwork more efficient, and help with creating better assessment tools, just to name a few topics. By measuring the maximum distance each liquid can stretch, students can easily rank the surface tension of various liquids and make inferences about the magnitude of IMFs present. To check for understanding, Part 1 ends with asking students to apply their recent knowledge by ranking the surface tension of decane, hexane, octane, and pentane. Herein lies the simplicity. The crosscutting concepts of patterns, energy and matter, and stability and change are called out as organizing concepts for these disciplinary core ideas. Chemical reactions, including rates of reactions and energy changes, can be understood by students at this level in terms of the collisions of molecules and the rearrangements of atoms. Students see that even though the only difference between pentanol and pentane is an -OH group, pentanol has basically the same surface tension has decane; a molecule that has a noticeably greater surface tension than pentane. The last part of this activity introduces students to the concept of hydrogen bonding by looking at how water molecules interact with one another (Figure 7). All rights reserved. Different equations existing in the literature were applied and calculated values were compared with the … With new evidence and an increased understanding of how the surface tension of alcohols compares to alkanes, Part 3 ends by asking students to rank the surface tension of a greater variety of molecules like methanol, ethanol, butanol, pentane, pentanol, hexane, hexanol, octane, octanol, decane, and decanol. The GIF below (figure 2) provides a great visual of this process.

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