This is a virtual lab in which you will be stepping through a series of experiments (see below), measuring data and doing calculations. You will turn in a data sheet that includes all 'measured' quantities (temperatures, masses, etc.) that you observe and/or use in some calculation. You must also (clearly labeled) answer all of the 'questions' given in each experiment.right click on teh following link: http://www.docott.com/files.142/labs.exams/phase.change.lab.blank.sheet.doc 'save' the file on your g drive (or locally) and then open it up. In this document, you will put all your answers. You will turn this experiment in before you leave the classroom!
There are no pre-lab questions, but you will want to read section 19.3 and 19.4 before you come to class.
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|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||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.|
|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.|