The production of bioethanol from cellulosic waste is described. The experiment is suitable for students in secondary school classroom settings and leads to bioethanol in a concentration high enough to burn the liquid. The experiment consists of three steps: (i) the cellulose of the waste material is converted to glucose by cellulase enzymes, (ii)…

In the 1960s, Tanzanian student Erasto Mpemba and his teacher published a paper with the title "Cool?" in this journal (Mpemba and Osborne 1969 "Phys. Educ." 4 172-5). They claimed that hot water freezes more quickly than cold water. The paper not only led to a wave of discussion, and more publications about this topic, but also to a whole series…

Liquid-free cryogenic devices are acquiring importance in basic science and engineering. But they can also lead to improvements in teaching low temperature and solid-state physics to graduate students and specialists. Most of the devices are relatively expensive, but small-sized equipment is slowly becoming available. Here, we have designed…

Studies regarding the whoosh bottle combustion experiment have largely focused on the detonation hazard of the demonstration, particularly with regards to fuel and container choice. Previous work has suggested that the fuel should be 2-propanol owing to its relatively cool flame characteristics. The current study has found that the combustion of…

In 1930, Einstein argued against the consistency of the time-energy uncertainty relation by discussing a thought experiment involving a measurement of the mass of the box which emitted a photon. Bohr seemingly prevailed over Einstein by arguing that Einstein's own general theory of relativity saves the consistency of quantum mechanics. We revisit…

New media technology becomes more and more important for our daily life as well as for teaching physics. Within the scope of our N.E.T. research project we develop experiments using New Media Experimental Tools (N.E.T.) in physics education and study their influence on students learning abilities. We want to present the possibilities e.g. of…

During a five-year period the authors taught over 100 students in a graduate course (The Nature of Science) counting toward teacher certification at the Harvard Graduate School of Education. Despite the fact that students had undergraduate degrees in the sciences, most of them found the application of models in science challenging and the…

This organic laboratory experiment introduces students to stereoselective enzyme reactions, resolution of enantiomers, and NMR analysis of diastereomers. The reaction between racemic 1-phenylethanol and vinyl acetate in hexane to form an ester is catalyzed by acylase I. The unreacted alcohol is then treated with a chiral acid and the resulting…

The surface plasmon wave is a surface wave confined at the interface between a dielectric and a metal. The excitation of the surface plasmon resonance (SPR) on a gold thin film is discussed within the Kretschmann configuration, where the coupling with the excitation light is achieved by means of a prism in total reflection. The electromagnetic…

Bertrand's paradox (Bertrand 1889 "Calcul des Probabilites" (Paris: Gauthier-Villars)) can be considered as a cautionary memento, to practitioners and students of probability calculus alike, of the possible ambiguous meaning of the term "at random" when the sample space of events is continuous. It deals with the existence of different possible…

The acid ionization constant, K[subscript a], of acetic acid and the base ionization constant, K[subscript b], of ammonia are determined easily and rapidly using a datalogger, a pH sensor, and a conductivity sensor. To decrease sample preparation time and to minimize waste, sequential aliquots of a concentrated standard are added to a known volume…

Although the siphon has been in use since ancient times, the exact mechanism of operation is still under discussion. For example, most dictionaries assert that atmospheric pressure is essential to the operation of a siphon rather than gravity. Although there is general agreement that gravity is the motivating force in a siphon, there is…

To diversify the measurement techniques of Avogadro's number in physics teaching, I propose a simple acoustic method for the experimental determination of Avogadro's number based only on the measurement of the speed of sound in metals, provided that their Debye temperatures are known. (Contains 2 figures.)

In this article we make some significant remarks on the experimental study of the absorption of gamma radiation passing through matter. These remarks have to do with the seemingly unexpected trend of the measured intensity of radiation versus the thickness of the absorber, which puzzles students and its explanation eludes many laboratory…

A simple wind speed measurement device, a paper anemometer, is fabricated based on the theory of standing waves. In providing the working profile of the paper anemometer, an experimental device is established, which consists of an anemometer sensor, a sound sensor, a microphone, paper strips, a paper cup, and sonic acquisition software. It shows…