This work presents the design of an inexpensive electronic system to measure water temperature and generate an experimental data set used to verify the fitting between experimental and theoretical curves of a water-cooling process. The cooling constant is computed with three different theoretical methods to check their efficiency and this approach…

In this paper a well-known experiment is considered that is used to demonstrate some aspects of water boiling. It is shown that the currently popular explanation is wrong and a better explanation is proposed, backed up with experimental data. Variations of the experiment are proposed that can be used for a more in-depth examination of the…

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…

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…

A newly developed laboratory learning program for high school chemistry courses is discussed, in which students discover the chemical mechanism governing exothermic phenomena during the reaction between a heating agent, namely, calcium oxide (CaO)--aluminum (Al) mixture, and water. Based on prior knowledge of simple heating agents such as CaO, the…

We present a sequence of two physics experiments, designed for use with secondary students, which investigate the specific heat of sand, both qualitatively and quantitatively, without a calorimeter. We use two LM35 temperature sensors and an Arduino prototype board for data acquisition. The results are good and allow teachers to discuss the…

The concept of equilibrium vapor pressure plays a key role in the general chemistry curriculum; it is among the first and most easily demonstrated examples of equilibrium and frequently caps off the first semester of general chemistry where it illustrates the properties of liquids and intermolecular forces. We report here simple modifications of…

A common misconception about dissolving is that heating and/or stirring are required for the dissolving process to occur. In this study, quantitative experimental evidence was collected and analyzed to demonstrate that neither heating nor stirring is required for dissolving. Educators can use the data and results in this study to address this…

When the thermal expansion of water is discussed in school or university lessons, functional relationships are often inferred without considering measurement uncertainties. Moreover, in some learning materials, the goal of experimentation and the experimental setup do not match. This creates the wrong picture of scientific practice. In this…

An attempt to calibrate a conventional oven led to making a measurement of a thermophysical property of water using items found in the author's home. Specifically, the ratio of the energy required to heat water from the melting point to boiling to the energy required to completely boil away the water is found to be 5.7. This may be compared to the…

Water exhibits a maximum in density at normal pressure at around 4° degree temperature. This paper demonstrates that during cooling, at around 4 °C, the temperature remains constant for a while because of heat exchange associated with convective currents inside the water. Superficial approach implies it as a new anomaly of water, but actually it…

Many of us are familiar with the demonstration of boiling water in a paper cup held over a candle or a Bunsen burner; the ignition temperature of paper is above the temperature of 100°C at which water boils under standard conditions. A more dramatic demonstration is melting tin held in a playing card. This illustration is from Tissandier's book on…

Under certain conditions a body of hot liquid may cool faster and freeze before a body of colder liquid, a phenomenon known as the Mpemba Effect. An initial difference in temperature of 3.2 °C enabled warmer water to reach 0 °C in 14% less time than colder water. Convection currents in the liquid generate a temperature gradient that causes more…

Why Does It Take Longer to Boil Potatoes at High Altitudes? This column provides background science information for elementary teachers. This month's issue looks at why water boils at different temperatures at different altitudes.

This work presents a simple analogue waterproof temperature probe design and its electronic interfacing with a computer to compose a data acquisition system for water temperature measurement. It also demonstrates the system usage through an experiment to verify the water heating period with an electric heater and another to verify the Newton's law…