Undergraduate Physical Chemistry Laboratory Research Articles

An Inquiry-Based Computational Chemistry Activity for the Undergraduate Physical Chemistry Laboratory

An Inquiry-Based Computational Chemistry Activity for the Undergraduate Physical Chemistry Laboratory

Physical Chemistry Lab for Data Analysis of COVID-19 Spreading Kinetics in Different Countries.

The COVID-19 pandemic has passed. It gives us a real-world example of kinetic data analysis practice for our undergraduate physical chemistry laboratory class. It is a great example to connect this seemingly very different problem to the kinetic theories for chemical reactions that the students have learned in the lecture class. At the beginning of the spring 2023 semester, we obtained COVID-19 kinetic data from the "Our World in Data" database, which summarizes the World Health Organization (WHO) data reported from different countries. We analyzed the effective spreading kinetics based on the susceptible-infectious-recovered-vaccinated (SIR-V) model. We then compared the effective rate constants represented by the real-time reproduction numbers ( ) underlining the reported data for these countries and discussed the results and the limitations of the model with the students.

Experiences with an Inquiry-Based Ionic Liquid Module in an Undergraduate Physical Chemistry Laboratory.

The topic of ionic liquids is typically not taught at the undergraduate level. Many properties, such as conductivity, vapor pressure, and viscosity, of these so-called "green solvents" are unique compared to traditional molecular solvents. Using active learning techniques, we introduced an ionic liquid module in the physical chemistry laboratory where their structures and physical properties, namely, viscosity, conductivity, and vapor pressure, were explored in relation to molecular solvents. Summative and formative assessments show that a majority of the participants were able to grasp the key concepts of ionic liquids. We envision that our methods and strategies can be one of the building blocks of introducing ionic liquids into the undergraduate chemistry curriculum.

Analysis of Large Data Sets in a Physical Chemistry Laboratory NMR Experiment Using Python.

We describe an update to an experiment demonstrating low-field NMR spectroscopy in the undergraduate physical chemistry laboratory. A Python-based data processing and analysis protocol is developed for this experiment. The Python language is used in fillable worksheets in the notebook software JupyterLab, providing an interactive means for students to work with the measured data step by step. The protocol teaches methods for the analysis of large data sets in science or engineering, a topic that is absent from traditional chemistry curricula. Python is among the most widely used modern tools for data analysis. In addition, its open-source nature reduces the barriers for adoption in an educational laboratory.

Feasibility of Using a Multicompartment Electrochemical Cell for Determination of Solubility Product Constants of Silver Salts from Potentiometric Measurements: A Directed Study in the Undergraduate Physical Chemistry Laboratory

Feasibility of Using a Multicompartment Electrochemical Cell for Determination of Solubility Product Constants of Silver Salts from Potentiometric Measurements: A Directed Study in the Undergraduate Physical Chemistry Laboratory

Coherent Phonons in Antimony: An Undergraduate Physical Chemistry Solid-State Ultrafast Laser Spectroscopy Experiment

Ultrafast laser pump-probe spectroscopy is an important and growing field of physical chemistry that allows the measurement of chemical dynamics on their natural timescales, but undergraduate laboratory courses lack examples of such spectroscopy and the interpretation of the dynamics that occur. Here we develop and implement an ultrafast pump-probe spectroscopy experiment for the undergraduate physical chemistry laboratory course at the University of California Berkeley. The goal of the experiment is to expose students to concepts in solid-state chemistry and ultrafast spectroscopy via classic coherent phonon dynamics principles developed by researchers over multiple decades. The experiment utilizes a modern high-repetition rate 800 nm femtosecond Ti:Sapphire laser, split pulses with a variable time delay, and sensitive detection of transient reflectivity signals. The experiment involves minimal intervention from students and is therefore easy and safe to implement in the laboratory. Students first perform an intensity autocorrelation measurement on the femtosecond laser pulses to obtain their temporal duration. Then, students measure the pump-probe reflectivity of a single-crystal antimony sample to determine the period of coherent phonon oscillations initiated by an ultrafast pulse excitation, which is analyzed by fitting to a sine wave. Due to the disruption of in-person instruction caused by the COVID-19 pandemic, during those semesters students were provided the data they would have obtained during the experiment to analyze at home. Evaluation of student written reports reveals that the learning goals were met, and that students gained an appreciation for the field of ultrafast laser-induced chemistry.

The Briggs–Rauscher Reaction: A Demonstration of Sequential Spatiotemporal Patterns

The Briggs–Rauscher reaction is a popular demonstration to illustrate chemical oscillations in laboratories, classrooms, and public seminars because of its simplicity and visual appeal. Here, we adapt the Briggs–Rauscher reaction to present reaction–diffusion–convection patterns in the undergraduate general or physical chemistry laboratory. By maintaining the ratio between malonic acid and potassium iodate concentrations as 0.2 in an uncovered Petri dish, sequential patterns (transient dendritic patterns and rotating dendritic patterns) can be observed, which are induced by the interaction of reaction, diffusion, and convection. This beautiful demonstration captures students’ attention and inspires reflection and discussion about similar phenomena in nature as well as the wealth of behaviors in systems far from equilibrium.

Reverse Micelles as Templates for the Fabrication of Size-Controlled Nanoparticles: A Physical Chemistry Experiment

Synthesis and characterization of nanomaterials yields opportunities for instruction of related topics in solution chemistry and materials science, as well as spectroscopy connecting to band theory, the particle in a box quantum mechanical model, and thermodynamics. In collaboration with an undergraduate research assistant, we have developed a synthesis experiment that investigates the use of reverse micelles as reaction templates for the preparation of size-controlled nanomaterials through simple, controlled precipitation reactions. This experiment is designed for an undergraduate physical or inorganic chemistry laboratory course. The proposed method boasts several advantageous features, including simplicity, functionality both at low temperature and in the presence of oxygen, applicability to a wide variety of compounds including semiconductors and colloidal metals, and precise control of particle size. To demonstrate our method, we chose CdSe as a model system due to its readily observable size-dependent optical effects. The particles produced are well-controlled and show high optical quality. Additionally, the use of reverse micelles allows us to further broaden the scope of this assessment, incorporating other key topics including ligand–metal chelation, nucleation/growth kinetics, thermodynamics, surfactant chemistry, and hydrodynamics.

Comparing Classical Water Models Using Molecular Dynamics To Find Bulk Properties

A computational chemistry exercise for the undergraduate physical chemistry laboratory is described. In this exercise, students use the molecular dynamics package Amber to generate trajectories of bulk liquid water for 4 different water models (TIP3P, OPC, SPC/E, and TIP4Pew). Students then process the trajectory to calculate structural (radial distribution functions) and dynamic (diffusion coefficients) properties of water that they compare to experimental values and to the other models. On the basis of these comparisons, students are also able to draw conclusions regarding the relative efficacy of these water models at modeling properties of real water.

Determining the Speed of Sound and Heat Capacity Ratios of Gases by Acoustic Interferometry

In this paper, we describe an experiment for the undergraduate physical chemistry laboratory in which students determine the speed of sound in the gases He, N2, CO2, and CF3CH2F. The experimental apparatus consists of a closed acrylic tube containing the gas under study. White audio noise is injected into one end of the tube, and the sound amplitude is recorded as a function of time at the other end. The data are recorded and Fourier transformed in real time with a spectrum analyzer application on an Apple iPad. The resulting frequency spectrum of the cavity standing waves is used to determine the speed of sound in the gas by least-squares fitting, with experimental values that fall within about 0.2% or less of the accepted values. The speed of sound is related to the heat capacity ratio in the ideal gas limit, providing students with quantitative evidence of the nonideality of the gases at ambient pressure and temperature. The experiment demonstrates the power and accuracy of interferometry and Fourier a...

Adapting and Modifying the Apparatus for Students To Accurately Determine the Freezing Point of a Solvent and Solution

An improved apparatus for measuring freezing points has been developed. Compared to the traditional Beckmann freezing point instrument, the improved one overcame prior difficulties with solidification of liquid and made the solid–liquid equilibrium reversible with heat compensation from a heating tube. The reliability and accuracy were carefully examined by determining the freezing point of the solvent and solution, as well as calculating the molar mass of the solute. It was found that the molar mass was in good agreement with the literature data. Thus, this improved device can effectively and successfully be used in undergraduate physical chemistry laboratory courses.

Anisotropic Rotational Diffusion Studied by Nuclear Spin Relaxation and Molecular Dynamics Simulation: An Undergraduate Physical Chemistry Laboratory

Laboratories studying the anisotropic rotational diffusion of bromobenzene using nuclear spin relaxation and molecular dynamics simulations are described. For many undergraduates, visualizing molecular motion is challenging. Undergraduates rarely encounter laboratories that directly assess molecular motion, and so the concept remains an abstraction. Spin relaxation and molecular dynamics simulations are complementary tools in studying molecular motion in solution. Simulations allow direct visualization of motion. Comparison of simulation results to experimental spin relaxation results enables discussion of the strengths and weaknesses of each technique. Performance of spin relaxation experiments in addition broadens undergraduate perceptions of the utility of NMR spectroscopy. Laboratories which enable the study of the motion of small molecules by both techniques are presented.

A Simple Molecular Dynamics Lab To Calculate Viscosity as a Function of Temperature

A simple molecular dynamics experiment is described to demonstrate transport properties for the undergraduate physical chemistry laboratory. The AMBER package is used to monitor self-diffusion in n-hexane. Scripts (available in the Supporting Information) make the process considerably easier for students, allowing them to focus on the simulations and their meaning. Mean-squared displacements are determined as a function of simulation time for 250 ps in a small simulation box at a variety of temperatures. From these, the Einstein–Smoluchowski and Stokes–Einstein relationships are used to determine the viscosity, which can be directly compared to literature values. The needed trajectories can be calculated in less than 1 h and analyzed in a second hour, leaving a third hour for further explorations as appropriate.

Measuring Heterogeneous Reaction Rates with ATR-FTIR Spectroscopy To Evaluate Chemical Fates in an Atmospheric Environment: A Physical Chemistry and Environmental Chemistry Laboratory Experiment

This paper reports an undergraduate laboratory experiment to measure heterogeneous liquid/gas reaction kinetics (ozone-oleic acid and ozone-phenothrin) using a flow reactor coupled to an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometer. The experiment is specially designed for an upper-level undergraduate Physical Chemistry laboratory course and may be incorporated in environmental chemistry and toxicology laboratory courses as well. From the experiment, students can measure heterogeneous reaction rates, calculate reactive uptake coefficients, and evaluate the lifetime of chemicals in an atmospheric environment, which is conducive to their understanding of several important concepts related to physical chemistry and environmental chemistry.

Vibrational Spectroscopy of the CCl4 ν1 Mode: Effect of Thermally Populated Vibrational States

In our previous article on CCl4 in this Journal, we presented an investigation of the fine structure of the symmetric stretch of carbon tetrachloride (CCl4) due to isotopic variations of chlorine in C35Clx37Cl4–x. In this paper, we present an investigation of the contributions from both the v = 0 to v = 1 excitation and the v = 1 to v = 2 excitation. We report the calculation of spectral contributions from excited state vibrational transitions (hot bands). All calculations and discussion are appropriate for the undergraduate physical chemistry laboratory as either an independent dry lab or a supplement to a pre-existing vibrational spectroscopy lab.

Observing Tin–Lead Alloys by Scanning Electron Microscopy: A Physical Chemistry Experiment Investigating Macro-Level Behaviors and Micro-Level Structures

Scanning electron microscopy (SEM) was introduced into undergraduate physical chemistry laboratory curriculum to help students observe the phase composition and morphology characteristics of tin–lead alloys and thus further their understanding of binary alloy phase diagrams. The students were captivated by this visual analysis method, which allowed them to more fully consider the relationship between macroscopic behaviors and microscopic structures of materials. During this process, the abilities of critical thinking were inspired, and a spirit of team work came into being.

X-ray Diffraction of Intermetallic Compounds: A Physical Chemistry Laboratory Experiment

Here we describe an experiment for the undergraduate physical chemistry laboratory in which students synthesize the intermetallic compounds AlNi and AlNi3 and study them by X-ray diffractometry. The compounds are synthesized in a simple one-step reaction occurring in the solid state. Powder X-ray diffractograms are recorded for the two compounds as well as for the elements Al and Ni, all of which have cubic crystal structures. The students analyze the measured spectra to determine both the type of cubic lattice present and the unit cell dimension for comparison with the literature. The experiment demonstrates the utility of X-ray diffraction for structure determination.

Vibrational Spectroscopy of the CCl4 v1 Mode: Theoretical Prediction of Isotopic Effects

Raman spectroscopy is a powerful experimental technique, yet it is often missing from the undergraduate physical chemistry laboratory curriculum. Tetrachloromethane (CCl4) is the ideal molecule for an introductory vibrational spectroscopy experiment and the symmetric stretch vibration contains fine structure due to isotopic variations of the molecule according to C35Clx37Cl4–x. We report simple theoretical predictions of the fine structure, calculation of Raman differential scattering cross sections, and discussion of the inherent asymmetry in the v1 mode resulting from the different isotopes of chlorine. All calculations and discussion are appropriate for an undergraduate physical chemistry laboratory as either an independent dry lab or a supplement to a pre-existing vibrational spectroscopy lab.

Studying the Binomial Distribution Using LabVIEW

This undergraduate physical chemistry laboratory exercise introduces students to the study of probability distributions both experimentally and using computer simulations. Students perform the classic coin toss experiment individually and then pool all of their data together to study the effect of experimental sample size on the binomial distribution. Simulations of the coin toss experiment are also performed using the software package LabVIEW. LabVIEW facilitates the creation of complex computer programs in a short period of time, even by beginner programmers. Histograms in LabVIEW are displayed in real time with students adjusting the number of simulated coin tosses on the fly using a virtual knob or a slider, up to 1 million individual trials. This allows the students to see firsthand the evolution of the binomial distribution into the Gaussian distribution with a large sample size.

Using Raman Spectroscopy and Surface-Enhanced Raman Scattering To Identify Colorants in Art: An Experiment for an Upper-Division Chemistry Laboratory

Surface-enhanced Raman scattering (SERS) studies of art represent an attractive way to introduce undergraduate students to concepts in nanoscience, vibrational spectroscopy, and instrumental analysis. Here, we present an undergraduate analytical or physical chemistry laboratory wherein a combination of normal Raman and SERS spectroscopy is used to identify both inorganic and organic fluorescent colorants in an oil painting. On the basis of their experimental observations, students make procedural decisions to adjust acquisition settings and use SERS, thereby enabling the successful identification of unknowns. This laboratory engages undergraduate students by applying what they have learned about quantum mechanics, nanoscience, and spectroscopy to the real-world, problem-solving context of art conservation.