Study Of Intermolecular Forces Research Articles

Pengembangan Video Gaya Antarmolekul Berbasis Multipel Representasi untuk Mengatasi Miskonsepsi

Intermolecular forces are one of the topics in basic chemistry. Intermolecular forces consist of abstract concepts that require multiple representations (macroscopic, submicroscopic, and symbolic) to visualize those concepts. Moreover, the multiple representations are needed to help students understand the abstract concepts of intermolecular forces. Multiple representations were presented as pictures, diagrams, and animation in the videos. The aims of this research are to develop a video of intermolecular forces based on multiple representations and to determine the level of validity and student’s responses to the video. This study employs the 4D method formulated by Thiagarajan which consist of 4 stages. However, this study only adopted 3 stages; define (to know the problem), design (manufacture of product to solve the problem), and development (to determine the level of validity and student responses). The instruments used in this study were the validity and the response questionnaires. Data collected were then analyzed using the percentage criteria proposed by Riduwan. The video provides the conceps and real-life example of the London forces and hydrogen bonding. Video validation shows the level of subject matter validity is 95,38%, media validity is 98,89%, and language validity is 91,11%, where all the aspects were very valid criteria. Every aspect is validated by 3 experts. Student responses on a limited scale by 7 students show a percentage of 87,8% and a large scale by 20 students of 88,9% with very good criteria. Based on the result, the video can be used in the study of intermolecular forces

Primary and Secondary Hydration Forces between Interdigitated Membranes Composed of Bolaform Microbial Glucolipids.

To better understand lipid membranes in living organisms, the study of intermolecular forces using the osmotic pressure technique applied to model lipid membranes has constituted the ground knowledge in the field of biophysics since four decades. However, the study of intermolecular forces in lipid systems other than phospholipids, like glycolipids, has gained a certain interest only recently. Even in this case, the work generally focuses on the study of membrane glycolipids, but little is known on new forms of non-membrane functional compounds, like microbial bolaform glycolipids. This work explores, through the osmotic stress method involving an adiabatic humidity chamber coupled to neutron diffraction, the short-range (<2 nm) intermolecular forces of membranes entirely composed of interdigitated glucolipids. Experiments are performed at pH 6 when the glucolipid is partially negatively charged and for which we explore the effect of low (16 mM) and high (100 mM) ionic strength. We find that this system is characterized by primary and secondary hydration regimes insensitive and sensitive to ionic strength, respectively, and with typical decay lengths of λH1 = 0.37 ± 0.12 nm and λH2 = 1.97 ± 0.78 nm.

Estudio del tratamiento del enlace químico en los libros de texto españoles

En este trabajo se presenta un análisis del tratamiento del concepto de enlace químico en los libros de texto de Educación Secundaria en España. Se ha realizado un estudio de caso comparativo de tres de las editoriales más utilizadas con mayor frecuencia, para ello se elaboró una rúbrica con seis categorías: secuenciación de los contenidos, causa de la formación del enlace, terminología utilizada, clasificación de las sustancias según tipo de enlace, modelos de enlace y estudio de las fuerzas intermoleculares. Se concluye que entre las editoriales no hay diferencias en cuatro de los seis puntos, pero sí en: terminología empleada y el tratamiento de las fuerzas intermoleculares. Se aconseja al profesorado hacer uso de la rúbrica diseñada para analizar el tratamiento del enlace químico en los libros de texto y decidir cuál utilizar en sus clases.

Novel tip modification method for measurement of the adhesive force between a silanized surface and a locally modified tip using atomic force microscopy

Chemical force microscopy using probe tips subjected to liquid-phase chemical modification enables the study of intermolecular forces on a nanoscale, as well as imaging of the chemical inhomogeneity of a sample’s surface with high spatial resolution. However, in adhesive force measurements, the adhesive force between the tip and the sample could easily be affected by interactions caused by molecules in both the contact and the noncontact parts. A novel method involving local chemical modification of the tip is presented. The method is performed by adding a solution of a modification reagent in ethanol when the cleaned tip is approaching the substrate’s surface. The adhesive forces between the substrate’s surface and various types of tips were investigated using atomic force microscopy. This novel method could be helpful for increasing the resolution of chemical force microscopy and for measuring the contact area between the tip and the substrate’s surface.

Modulated multipolar structures in magnetic arrays

Electric and magnetic multipole moments are important quantities in studies of intermolecular forces, and electrostatic and magnetostatic potentials. The experimental determination of multipole moments in multipole–multipole coupling is difficult and therefore the theoretical prediction of these quantities is important. The aim of the present review is to give a general theoretical description of multipolar ordering on two-dimensional periodic and aperiodic lattices. After an introduction to the role of multipolar interactions in magnetic nanoarrays in the first part of this article, the static multipole expansions in Cartesian and spherical coordinates are outlined. Next, the established numerical approach for the calculation of multipolar ground states, i.e. Monte Carlo simulations, are summarized. Special emphasis is put on the review of ground states in multipolar systems consisting of moments of odd parity relevant for the magnetized or polarized particle ensembles. We demonstrate that higher-order interactions considerably change the dipolar ground states of in-plane magnetized arrays. While in periodic triangular, square and kagome arrays the higher-order interactions induce three- or four-fold in-plane anisotropy, on a Penrose tiling with ten-fold symmetry the multipolar terms do not seriously affect the dipolar order.

Multipolar Ordering in Electro‐ and Magnetostatic Coupled Nanosystems

Electric and magnetic multipole moments and polarizabilities are important quantities in studies of intermolecular forces, non-linear optical phenomena, electrostatic, magnetostatic or gravitational potentials and electron scattering. The experimental determination of multipole moments is difficult and therefore the theoretical prediction of these quantities is important. Depending on purposes of the investigation several different definitions of multipole moments and multipole-multipole interactions are used in the literature. Because of this variety of methods it is often difficult to use published results and, therefore, even more new definitions appear. The first goal of this review is to give an overview of mathematical definitions of multipole expansion and relations between different formulations. The second aim is to present a general theoretical description of multipolar ordering on periodic two-dimensional lattices. After a historical introduction in the first part of this manuscript the static multipole expansion in cartesian and spherical coordinates as well as existing coordinate transformations are reviewed. On the basis of the presented mathematical description multipole moments of several symmetric charge distributions are summarized. Next, the established numerical approach for the calculation of multipolar ground states, namely Monte Carlo simulations, are reviewed. Special emphasis is put on the review of ground states in multipolar systems consisting of moments of odd or even order. The last section is devoted to the magnetization reversal in dense packed nanomagnetic arrays, where the magnetic multipole-multipole interactions play an important role. Comparison between the theory and recent experimental results is given.

Solvation forces and colloidal stability: A combined Monte Carlo and density functional theory approach

Osmotic stress (OS) techniques have found wide application in the crystallization of proteins, the study of intermolecular forces between biocolloids, and in studies of the role of solvent in molecular recognition events. In these cases, the role of the solvent is not well understood. We present here a combined Monte Carlo simulation and smoothed density functional theory approach with which model colloid–solvent mixtures may be studied in a potential of mean force approximation. In particular, our simulations focus on parallel cube colloids in Lennard-Jones solvents. We have applied this approach to simulate some OS experiments in which the dependence of the intermolecular separation (h) of DNA strands in aqueous solutions on an applied osmotic pressure (Π) have been measured. Our simulations demonstrate that an underlying oscillatory solvation potential qualitatively produces the features of Π–h relationships observed in the experiments. In particular, increasing Π produces a transition to a more dense colloidal crystal. More importantly, the transition Π decreases with increasing temperature as observed in experiments. In addition, hydrostatic pressure pb and Π are shown to operate conversely in isothermal solvent controlled OS experiments. In addition to characterizing some key features of solvent controlled processes, these simulations reconcile OS experiments with surface forces apparatus (SFA) experiments, and suggest new experimental routes to studying intermolecular forces.

Chapter 6. Spectroscopic studies of intermolecular forces in dense phases

Chapter 6. Spectroscopic studies of intermolecular forces in dense phases

Chapter 7. Spectroscopic studies of intermolecular forces in dense phases

Chapter 7. Spectroscopic studies of intermolecular forces in dense phases

Nonreactive Molecular Encounters

Low-energy molecular collisions are discussed from a point of view that emphasizes the role of the internal degrees of freedom of the colliding molecules. The theory centers attention on the mechanism of energy transfer from kinetic energy of relative motion into internal energy and vice versa. It is shown that irrespective of the over-all energy transfer (which may be zero), the collision event proceeds via steps of energy migration between internal and relative degrees of freedom. This feature is absent in the available first-order theories. An approximation scheme which includes this feature even in first order is suggested, and a self-consistent-field scheme where each collision partner moves in the average field of the other partner is discussed. The migration of kinetic energy into internal degrees of freedom results in the temporary formation of bound states. Such intermediates are of importance in the study of intermolecular forces, vibrational excitations, contact charge-transfer complexes, and three-body recombinations. The collision of two hydrogen atoms is discussed in the adiabatic approximation, where the temporary bound state is due to charge redistribution. The mechanism of three-body recombination is discussed and a recombination rate constant is calculated.