1,720,977 research outputs found
CP/CV Ratios Measured by the Sound Velocità Method Using Calculator Based Laboratory Technology
No full textThe speed of sound in a gas depends on its temperature, molecular weight and γ=Cp/Cv, ratio of heat capacity at a constant pressure to heat capacity at constant volume. The γ value for air, oxygen, nitrogen, argon and carbon dioxide was determined by measuring the velocity of the sound through the gases at room temperature. The sound velocity is measured with a microphone using Calculator-Based Laboratory (CBL) Technology
Modelli per l’agitazione termica
No full textModels that can help to understand the mechanisms of some phenomena that occur in liquids, such as evaporation and distillation, and some aspects of the kinetic theory of gases are describe
Una scuola a due velocità. risultati delle rilevazioni nazionali ed internazionali sulle competenze degli studenti in Sardegna
No full textA Physical Model to Help Explain Evaporation
No full textOne of the basic ideas when studying science is that matter is composed of particles (atoms or molecules) and these are in a constant state of agitation. In the solid or liquid state the molecules are attracted to each other, while in the gaseous state they have sufficient energy to overcome the forces of cohesion and can move away from one another
Thermal Expansion: Using Calculator-Based Laboratory Tecnology To Observe the Anomalous Behavior of Water
No full textThis is a simple experiment to observe variations in the density of water and other liquids at different temperatures with CBL technology. Using it one can observe the anomalous behaviour of water at temperatures between 0°C and 4°
Using Peltier cell to study solid-liquid-vapour transitions and supercooling
No full textWe propose an apparatus for teaching experimental thermodynamics in
undergraduate introductory courses, using thermoelectric modules and a
real-time data acquisition system. The device may be made at low cost,
still providing an easy approach to the investigation of liquid–solid and
liquid–vapour phase transitions and of metastable states (supercooling). The
thermoelectric module (a technological evolution of the thermocouple) is by
itself an interesting subject that offers a clear example of both thermo-electric
(Seebeck effect) and electro-thermal (Peltier effect) energy transformation.
We report here some cooling/heating measurements for several liquids and
mixtures, including water, salt/water, ethanol/water and sodium acetate,
showing how to evaluate the phenomena of freezing point depression and
elevation, and how to evaluate the water latent heat
Big Pile or Small pile?
No full textThe construction of a voltaic pile (battery) is a simple laboratory activity that commemorates the invention of this important device and is of great help in teaching physics
STRUCTURAL AND THERMODYNAMIC ASPECTS OF GLASS-FORMATION IN CU-TI-H - ROLE OF HYDROGEN IN MECHANICAL ALLOYING
No full textThe results of experiments of milling elemental powders of Cu and Ti in the presence of hydrogenated Ti are reported. A mixture of an amorphous phase and TiH2 was obtained by grinding gamma-CuTi under H-2. Ball milling was performed on ternary mixtures of Cu, Ti and TiH2 under Ar. Complete amorphization occurred at low concentrations of TiH2; otherwise, an amorphous phase coexisting with unreacted hydride was obtained. The structure of the powders was checked at steps during milling by correlating X-ray diffraction and thermal analysis data. The free energy of formation of the alloys, estimated at 300 K along a section of the Cu-Ti-H phase diagram, shows a driving force for amorphization at low hydrogen content. All ternary Cu-Ti-H hydrides, both crystalline and amorphous, are metastable with respect to a mixture of TiH2 and Cu-Ti intermetallics and the possibility of a phase separation in the amorphous hydrogenated alloy is outlined
STRUCTURAL-CHANGES INDUCED BY THE MECHANICAL ALLOYING OF CRYSTALLINE METAL POWDERS
No full textWe report structural results of mechanical alloying binary mixtures of pure elemental powders as a function of milling time. X-ray line broadening techniques are used to follow the lattice destabilization caused by interdiffusion of elements, which is favoured by a negative heat of mixing. Experimental evidence is outlined on the formation of highly distorted solid solutions and intermetallic compounds, which, due to the milling action, collapse to an amorphous condition when a critical density of defects is reached
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