4.2 The density of a sample of poly(ethylene terephthalate), PET, is measured to be 1.468 g/cm³. A. What fraction of this PET is amorphous? B. What is the density of a PET sample that is 45% crystalline? The density of amorphous PET has been reported to be 1.336 g/cm³ and crystalline PET as 1.514 g/cm³. 4.3 Two copolymers were synthesized that contain 42 wt% polyethylene and 58 wt% polypropylene. The first polymer is rigid and opaque, while the second is soft and transparent. Give two plausible explanations of the difference in properties despite the copolymers having the same composition (and molecular weight). {I have three possible answers} 4.4 Traditional materials science textbooks (like used in MTE 271, if you took that class) are concerned mostly with metals and ceramics instead of polymers. There is a great deal of discussion about crystal structures (such as fcc or face-centered cubic atomic arrangements in crystals, etc.) and crystal defects in these books. While there are studies of crystal structures and defects in polymers, this is hardly mentioned in most polymer textbooks. Why are these much less important in polymers than in metals and ceramics? Hint: look up what a grain boundary is.
Ideal and Real Gases
Ideal gases obey conditions of the general gas laws under all states of pressure and temperature. Ideal gases are also named perfect gases. The attributes of ideal gases are as follows,
Gas Laws
Gas laws describe the ways in which volume, temperature, pressure, and other conditions correlate when matter is in a gaseous state. The very first observations about the physical properties of gases was made by Robert Boyle in 1662. Later discoveries were made by Charles, Gay-Lussac, Avogadro, and others. Eventually, these observations were combined to produce the ideal gas law.
Gaseous State
It is well known that matter exists in different forms in our surroundings. There are five known states of matter, such as solids, gases, liquids, plasma and Bose-Einstein condensate. The last two are known newly in the recent days. Thus, the detailed forms of matter studied are solids, gases and liquids. The best example of a substance that is present in different states is water. It is solid ice, gaseous vapor or steam and liquid water depending on the temperature and pressure conditions. This is due to the difference in the intermolecular forces and distances. The occurrence of three different phases is due to the difference in the two major forces, the force which tends to tightly hold molecules i.e., forces of attraction and the disruptive forces obtained from the thermal energy of molecules.
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