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Virtual Chemistry Experiments

Phase Changes

Topic Concepts Experiment
Heating Curve The processes that occur when a substance is heated are explained. A heating curve is recorded for a substance, which is displayed to illustrated the accompanying phase changes. The viewer is asked to determine the melting point, boiling point, and enthalpies of fusion and vaporization.
Vapor Pressure The liquid-gas and solid-gas equilibria are examined and the Claussius-Clapeyron is presented. The vapor pressure of ethanol is measured at various temperatures. A Classius-Clapeyron plot is prepared, and the viewer is asked to determine the normal boiling point and standard enthalpy and entropy of vaporization for ethanol.
Phase Diagram: Part 1 The properties of a phase diagram are described. The viewer is asked to determine the stable phase at various temperatures and pressures.
Phase Diagram: Part 2 The effect of crossing a phase line in a phase diagram is discussed. A sample is heated isobarically such that the process crosses a phase line in the phase diagram. The viewer is asked to determine the sublimation temperature at the experimental pressure.
Phase Diagram: Part 3 The effect of crossing a phase line in a phase diagram is discussed. A sample is compressed isothermally such that the process crosses a phase line in the phase diagram. The viewer is asked to determine the pressure at which the phase change occurs at the experimental temperature.
Phase Diagram: Part 4 The triple point is defined and its significance is discussed. Temperature or pressure changes are used to drive a substance through the triple point. The viewer is asked to determine the triple-point temperature and pressure.
Phase Diagram: Part 5 The critical point is defined and its significance is discussed. The transition between a liquid and gas is examined via two different routes, one of which crosses a phase line and one of which does not (passing through the super-critical region instead). Colors are used to represent the sample density and illustrate how it is possible to convert a sample from a liquid to a gas (or vice-versa) without producing a phase-change reaction.
Phase Diagram The features of a phase diagram are described. A phase diagram is presented along with a sample confined in a cylinder with a movable barrier. The viewer may alter the temperature and pressure of the sample in order to explore the features of the phase diagram.

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© Copyright 2001,2009 David N. Blauch
Last updated Tuesday April 22 2014