PC-Praktikum

• flows like a liquid
• molecules are oriented like in a crystal

Unabhängigkeit einer Eigenschaft von der Richtung.

Energie, die Notwendig ist, um 1 kg eines Stoffes um 1 °C zu erwärmen.

\(c = {Q \over m*\Delta T}\), Einheit: J/(kg*K)

Several measurements of a sample need to be taken, where the sample is heated at different Heating Rates. By plotting the Onset Temp. of the melting vs. the heating rates, the melting point is found as the y-axis (where we have an infinitely slow heating rate).
 

 In order to calibrate the instrument and therefore get rid of systematic errors. We get a scaling factor, which we need to use for our measurements.

\(K_T={T_{lit.} \over T_{exp}}\)

solid state: conventional crystal, which is anisotropic (properties depend upon the direction)

smectic phase: well defined layers, which can slide over another (soap properties), still anisotropic

nematic phase: no layer structure, but the molecules still point in the same direction --> anisotropy

liquid phase: fully isotropic

The viscosity of a fluid is a measure of its resistance to gradual deformation by shear or tensile stress. It can be regarded as an internal force of resistance, that delays deformation of a liquid (ex. pouring). It is a result of intermolecular interactions.

Insoluble polymers due to cross-linking.

 It is the ordinary arithmetic mean of the molecular masses. It is calculated as: total weight of sample / number of molecules in sample

Determined by VPO or Viscosimetry,

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This quantitiy depends on the number and the size of the molecules. A larger molecule will have a larger contribution than a smaller one.

It is determined by light scattering of polymer solutions, where the intensity of the scattered light depends upon the number and the weight of the molecules.

Number average mol. weight is not influenced by the molecular weight of the molecules and only depends on the number of molecules, whereas weight average mol. weight depends on both.

They can only be the same for a monodispers polymer solution.

It is a measure for the change in concentration of the reactant or the change in concentration of the products per unit of time.

Ag2O/ Zn, Pb / PbO
 

• accept the energy from the excited fluorophore (emission of fluorophore and absorption of quencher have to overlap)
• be close enough to transfer the energy
• quencher must return to the ground state without emitting light. (transform into heat)

The reaction rate is independent of the concentration of the reactant.

The liquid has strong intermolecular forces, like for example H-Bridges --> low vatality --> low vapour pressure
 

Giltet für den Spezialfall von zwei Phasen, welche im Ggw stehen.

\({dp\over dT} = {\Delta H_{vap}\over T*(V^{g}-V^{l})}={\Delta S_{vap}\over (V^{g}-V^{l})}\)

Näherung bei C-C-Gleichung --> molares Volumen der Flüssigkeit ist vernachlässigbar.

Als zweites kann man für das Gasvolumen die ideale Gasgleichung anwenden.

Isoteniskop.

Flüssigkeit in einem Glaskolben. Dieser ist mit Druckmessung über ein U-Rohr verbunden, in welchem sich ebenfalls die zu untersuchende Flüssigkeit befindet. Durch Erhöhung der Temperatur des isothermen Gasraums steigt der Flüssigkeitsspiegel im U-Rohr. Durch Zufuhr von Neutralgas im Aussenraum wird der Druck ausgeglichen und der Druck kann vom Barometer abgelesen werden.

Fest, Flüssig, Gas und Plasma.

Eigenschaften von Plasma = keine Form und keine best. Volumen, elektrisch leitfähig, prod. elektrische Ströme und magnetische Felder.

• thermal equ.
• mech. equ. (p1=p2)
• diffuse equ. : chem. potentials are the same

Die molare Standardverdampfungsentropie der meisten unpolaren Stoffe beträgt am Siedepunkt unter 1.013mbar ungefähr 88JK-1mol-1.

Abweichungen sind durch starke WW zwischen den Molekülen zu erklären, wie z.B. H-Brücken.

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1. Gas consists of molecules with mass m, that move all the time with their random thermal motion
2. Size of the molecules is negligible
3. The only interaction between the molecules is through elastic collisions.

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\(P= P_0 *e^{-{M*g*h\over RT}}\)
 

Sie beschreibt den herrschenden Druck in einer isothermen Atmosphäre in Abhängigkeit der Höhe.

\(v = \sqrt{ 2RT\over M}\)

\(v = \sqrt{ 8RT\over \pi M}\)

\(\sqrt {v^2} = \sqrt{ 3RT\over M}\)