Two bodies initially at different temperatures gathered into an isolated container exchange heat and reach an equilibrium state with a common final temperature. During the process, the system is out of equilibrium and its intermediate temperature is not well defined. By conceiving a quasi-static process with infinitesimal steps from the initial to…

One way to develop a cross-curricular lesson is to select the most common mathematical formulas used in science and carefully develop and implement tasks that allow students to make connections between the mathematical representations and theoretical/physical science concepts. The slope-intercept formula, which is used to study relationships…

Spontaneity criteria for processes with useful (especially electrical) work have been discussed based on total differentials of thermodynamic functions. Reaction Gibbs energy ([Delta][subscript r]G) and electrochemical reaction Gibbs energy ([Delta][subscript r]G~) have been juxtaposed. Three-dimensional graphs showing the dependencies of…

Chemical equilibrium is one of the most important concepts in chemistry. The changes in properties of the chemical system at equilibrium induced by variations in pressure, volume, temperature, and concentration are always included in classroom teaching and discussions. This work introduces a novel, geometrical approach to understanding the…

The double-wall paper cup is an everyday object that can be used in the laboratory to study heat transfer. The experiment described here has been done by physics students aged 12-13 years; it can also be used in a different context to prompt debate about environmental issues.

It is well known that heat transfer between two objects results in a positive change in the total entropy of the two-object system. The second law of thermodynamics states that the entropy change of a naturally irreversible process is positive. In other words, if the entropy change of any process is positive, it can be inferred that such a process…

This is a companion to our previous paper in which we give a published example, based primarily on Perry's work, of a graph of ln "y" versus "t" when "y" is an exponential function of "t". This work led us to the idea that Lord Kelvin's (William Thomson's) estimate of the Earth's age was…

G, G°, [delta][subscript r]G, [delta][subscript r]G°, [delta]G, and [delta]G° are essential quantities to master the chemical equilibrium. Although the number of publications devoted to explaining these items is extremely high, it seems that they do not produce the desired effect because some articles and textbooks are still being written with…

This paper presents a comparative study of the thermal efficiencies of mechanical heat engines by using a graphical approach based on the pressure-volume ("P-V") diagram. Three types of idealized thermodynamic cycles--the Otto, the Diesel and the Brayton--are compared in pairs. Given the same temperature range within which the engines…

During the years 1873-1879, J. Willard Gibbs published his now-famous set of articles that form the basis of the current perspective on chemical thermodynamics. The second article of this series, "A Method of Geometrical Representation of the Thermodynamic Properties of Substances by Means of Surfaces," published in 1873, is particularly notable…

The thermodynamic equations used to define and compute the fugacity of a pure substance are depicted as processes on a semi-logarithmic plot of pressure vs. molar Gibbs energy (PG diagram) with isotherms for the substance behaving as an ideal gas superimposed. The PG diagram clearly demonstrates the physical basis for the definitions and the…

Cell water relationships are important topics to be included in cell biology courses. Differences exist in the control of water relationships in plant cells relative to control in animal cells. One important reason for these differences is that turgor pressure is a consideration in plant cells. Diffusion and osmosis are the underlying factors…

The use of qualitative graphs of Gibbs energy versus temperature is described in the context of chemical demonstrations involving phase changes and colligative properties at the general chemistry level. (Contains 5 figures and 1 note.)

Discusses the use of property diagrams as an instructional tool to help students understand and visualize important, complex thermodynamic relationships. Also discusses the approach used in preparing these diagrams, which were computer-generated as part of graduate students' research. (JN)

The kinetics experiments on the ligand-C[subscript 60] exchange reactions on (dihapto-[60]fullerene) pentacarbonyl tungsten(0), ([eta][superscript 2]-C[subscript 60])W(CO)[subscript 5], form an educational activity for the inorganic chemistry laboratory that promotes graphical thinking as well as the understanding of kinetics, mechanisms, and the…