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Intermolecular forces (IMFs) make up a fundamental concept of chemistry and one that is integral to students’ understanding of the properties and interactions of matter. Despite this, students struggle to apply IMFs to real phenomena in their world. Here we describe a first-semester general chemistry laboratory in which students functionalize the surface of glass slides and observe the interaction of water and heptane drops with the surface, allowing them to integrate IMF, molecular modeling, and causal mechanistic reasoning to explain observable and measurable phenomena. In the activity, students perform and describe a series of simple reactions that covalently bond the silane molecules acetoxypropyltrimethoxysilane and octyltrimethoxysilane to the glass surface. They then characterize the slides by adding drops of water to the modified slide, taking profile pictures with their cell phones, and determining the drop half angles from the pictures using ImageJ software. Students also added drops of heptane to the slides and observed their interactions with the slides, contrasting those with the interactions of the water drops. This lab activity invites students to consider the material of the lab on the macroscopic and submicroscopic levels as they describe the functionalization of glass slides, observe the interaction of the modified and unmodified slides with drops of water and heptane, and then construct explanations that reinforce their learning of IMFs and molecular structures. The experimental procedure and data collection proved to be robust, with most students producing data that were consistent with expectations and supported their claims about the IMFs between water molecules and between the water molecules and the surface. 

The phenomenon of fluorescence is very important from multiple standpoints in the chemical and biological sciences. This paper introduces an experiment in a first-semester chemistry laboratory course that uses a current biomedical research method, the detection of double-stranded DNA using the intercalator propidium iodide. Fluorescence is detected both using blacklight illumination and also with white light and a spectrometer, using the two excitation bands for propidium. This experiment also involves students obtaining DNA from strawberries and then determining the amount of DNA they have isolated using fluorescence methods. The experiment provides students with an initial experience in fluorescence-based analytical chemistry and the concepts of fluorescence as a quantum phenomenon. 

A key part of the practice of chemistry is the analysis of chemical composition, including through gravimetric analysis and spectrophotometry. However, the complexity of doing multiple calculations to obtain analytical evidence, such as that required to determine an empirical formula, presents a challenge if such analytical methods are to be understood by students and if they are to support meaningful learning about other chemical concepts and methods. In this study we investigate student use of spectrophotometry and gravimetric analysis to determine the number of water molecules in hydrates of copper (II) salts, a method previously described by Barlag and Nyasulu. Using phenomenography to analyze students reports through the lens of meaningful learning we identified four distinct perceptions and, within them, information of how students make sense of the complex analytical steps involved in the experiment. We identify how meaningful learning is present where students recognized that spectrophotometry was based on light-matter interactions (cognitive,) was faster and more accurate (psychomotor), and allowed students to express confidence in the process and their results (affective). However, it is also the case that meaningful learning was compromised where students had trouble conceptualizing spectrophotometry, saw it as a set of disconnected steps, and where they saw absorbance as a computer-generated value and not a property of the solution. This led to the perception that gravimetric analysis provided a more direct and understandable technique. We discuss the implications of these findings for chemistry education research (CER) and for curriculum development in the undergraduate teaching lab.