Floating and sinking (FS) is a key topic in science education, both at primary and secondary levels. The interpretation of FS phenomena, however, is challenging due to the difficulty of the scientific concepts and explanatory models involved (e.g., density, buoyancy), along with students' everyday experiences, which conflict with scientific…

The advantage of VLs lies in their capacity for simulating real-world lab experiences within a fully immersive digital environment, yet the uptake in rural schools in developing countries remains low. To understand this paradox, this study explores the perceptions of seven secondary school science teachers in a rural district in South Africa.…

The Förster resonance energy transfer (FRET) melting assay intends to evaluate the unfolding, denaturation process of DNA secondary structures, and its stabilization using compounds known as DNA binders, some of which are highly specific for G-quadruplex DNAs versus duplex DNAs. First, students determined the melting temperature (T[subscript m])…

The anomalous thermal expansion of water in the 0 °C-4 °C range is extremely important to life on Earth, but it is normally not presented experimentally in educational settings. This paper presents a simple experiment to explore the anomalous thermal expansion of water in the 0 °C-4 °C range and the heat exchange processes in natural bodies of…

An experiment to match five white solids with ascorbic acid, citric acid, potassium hydroxide, sodium chloride, and urea is reported here. This 4 h experiment is an integrated practice of two experimental techniques, calorimetry and titration. Students conduct an extensive literature search on the properties of the five compounds and plan the…

Recently, small computer fans have been demonstrated to be an effective method for teaching simple resistive circuits both qualitatively and quantitatively. The current through the fans is related to the rotational speed of the fans and allows multiple senses to be engaged (touch, sight, and hearing). Methods for learning simple circuits in an…

Is a suction cup at the bottom of a bathtub subject to an upward force from the surrounding water, even if there is no water under it? A student question, posted in a teacher facebook group on a Monday morning, led to a discussion involving 21 comments with 225 replies offered by 16 teachers during the next few days, including several simple…

A simple experiment is described to verify the current dependence of Ampère's law for a long straight current-carrying conductor. A narrow and long rectangular multi-loop design is used to increase the strength of the magnetic field in between the long sides. As expected, the magnetic field is found to be linearly proportional to the electric…

The study of buoyancy is common in physics classrooms. In the last 20 years, several educators have described, theoretically and experimentally, buoyant forces and Archimedes' principle, both in "The Physics Teacher" and elsewhere. However, as far as I know, no one has reported on the pedagogical implications and experimental results of…

An alternative way of introducing magnetism at all levels of education is proposed. It is stressed that magnetism can be introduced through the interaction between current-carrying conductors giving the students, at the same time, the possibility to measure the magnetic permeability [mu][subscript o]. Focusing on currents instead of permanent…

Protein PEGylation refers to the covalent binding of polyethylene glycol (PEG) moieties to a protein and has been increasingly applied, mainly in the biopharmaceutical industry. This technique may increase bioavailability and stability by decreasing immunogenicity and proteolytic attack. Given the industrial interest and the relevance of this…

In this work we study the motion of a small metal ball along an inclined multi-slotted track. Specifically, the effect of the slot width on the ball speed at the lower part of the track is analyzed in detailed both analytically and experimentally. Experimental results are in satisfactory agreement with the theoretical model.

This paper describes an experiment with two touching rotating disks, whose movement is followed by video analysis. Within the disks' movements, there are intervals with sliding and intervals without sliding, that is, intervals with frictional forces between the touching surfaces and intervals without it. This system configuration allows for…

The Griess assay is widely used by regulation agencies as an official method for nitrite quantification in water and food samples. In Brazil, the official method, which has been used to determine nitrite in food, was described by Instituto Adolfo Lutz (283/IV) in 1984. It uses 8 mL of reactants and provides 50 mL (reactants plus sample) of waste…

The practical two-step synthesis of 1-phenylthiourea is reported here as an undergraduate experiment for the organic synthesis laboratory. The reactions involved in 1-phenylthiourea preparation are very useful didactic examples to illustrate concepts relating to carbonyl substitution and addition, the effect of pH on solubility of organic…