Chemistry Properties of Matter PDF

Properties of Matter Dictionary definitions of chemistry usually include the terms matter, composition, and properties, as in the statement that chemistry is the science that deals with the composition and properties of matter. Properties Are the qualities or characteristics that can be used to...

Properties of Matter Dictionary definitions of chemistry usually include the terms matter, composition, and properties, as in the statement that chemistry is the science that deals with the composition and properties of matter. Properties Are the qualities or characteristics that can be used to differentiate one sample of matter from another. Chemistry (properties) can help us in understanding drug-receptor binding interactions, mechanisms of action, and side effects of medications. Drug physicochemical properties are useful in designing dosage forms and achieving drug stability. A/Physical properties Physical property: is one that a sample of matter displays without changing its composition. Thus, we can distinguish between the reddish brown solid, copper, and the yellow solid, sulfur, by the physical property of color. B/Chemical property Chemical property : is the ability (or inability) of a sample of matter to undergo a change in composition under stated conditions. Zinc reacts with hydrochloric acid solution to produce hydrogen gas and a solution of zinc chloride in water. 5-Physical state Solid, liquid, and gases are classified as different state of matter because each has a different way of organizing its atom and molecules. States of matter: the matter exists in three states(based on neutral atoms): 1- Solid state: It has a fixed shape and size. 2 - The liquid state: It has a fixed volume,and shape that changes with the shape of the vessel in which the liquid is placed. 3- Gas state: it has no fixed size or shape.  Plasma is a 4th state of matter. If you bombard any atom with enough energy, you'll kick the electrons off of it, creating an ionized plasma: the fourth state of matter. It is created by a process called Ionization which involves adding energy to a gas so that some of its electrons leave its atoms. It results in negatively charged electrons, and positively charged ions. Unlike the other states of matter, the charged particles in a plasma reacts strongly to electric and magnetic fields. Plasma is not a common state of matter here on Earth, but it may be the most common state of matter in the universe, according to the Jefferson Laboratory. Stars like the sun are essentially superheated balls of plasma.  Are made only in the lab. But there are two additional states of matter that exist: Bose-Einstein Condensates and Fermionic Condensates, the fifth and sixth states of matter. Bose-Einstein condensate(Also called superatom) it is a state of matter that occurs in certain particles at temperatures close to absolute zero.  As atoms cool, they behave more like waves and less like particles. When cooled enough, their waves expand and begin to overlap. This is similar to steam condensing on a lid when it is boiled. The water clumps together to form a drop of water, or condensate. The same occurs with atoms, only it is their waves that merge together. Bose-Einstein condensates are similar to laser light. However, instead of photons behaving in a uniform manner, it is the atoms that exist in perfect union. Like a drop of water condensing, the low-energy atoms merge together to form a dense, indistinguishable lump. As of 2011, scientists are just beginning to study the unknown properties of Bose-Einstein condensates. Just as with the laser, scientists will discover many uses for them that will benefit science and humanity.  Physical states of drug Drug molecules can exist in a variety of physical states, such as amorphous solid, crystalline solid, hygroscopic solid, liquid, or gas. The physical state of drug molecules is an important factor in drug formulation and delivery. Amorphous solid Any non-crystalline solid with atoms and molecules that are not organized in a particular lattice pattern—i.e., irregular—is an amorphous solid. Gel, plastic, and glass are examples of such solids. Amorphous solids have surfaces that are either curved or irregular, do not produce well-resolved x-ray diffraction patterns, and they melt at a wide temperature range.  Advantage : Compared to crystalline forms, amorphous forms have higher solubility and dissolution rates. Disadvantage : Amorphous solids can sometimes revert to more stable forms when stored. This instability can occur in dosage forms or during bulk processing.  E. g. Novobiocin : It is inactive when administered in crystalline form, but when they are administered in the amorphous form, absorption from the gastro intestinal tract proceeds rapidly with good therapeutic response. Crystalline solid Crystalline solid: In a crystalline solid, the arrangement of the particles is very regular. A three-dimensional network's repeating pattern is used to arrange these particles. Crystalline solids diffract x-rays, have sharp melting points, and have well-defined edges and faces. Crystalline make up the majority of solids, such as metals like copper, iron, and zinc and ionic compounds like sodium chloride and zirconia.  Many drugs exist in the crystalline solid state due to reasons of stability and ease of handling during the various stages of drug development. Crystalline solids can exist in the form of polymorphs, solvates or hydrates. A drug molecule can form several The crystalline forms of drugs can be used due crystalline phases, which are to their greater stability than the called polymorphs. corresponding amorphous form Polymorphs have the same chemical composition, but a For example, the crystalline form of penicillin G different internal structure. as a potassium or sodium salt is significantly more stable and results in an excellent therapeutic response than a morphic form. Hygroscopic solid Hygroscopicity : Is the ability of a substance to absorb or adsorb moisture from the environment. Example NaOH Many drugs, especially the water-soluble salt forms, tend to absorb moisture from the air. Adsorption and moisture content are dependent on humidity, temperature, surface area, exposure and mechanism of moisture absorption. Deliquescence the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution. Deliquescent materials : Sodium Hydroxide, Zinc Chloride, Iron(iii) Chloride, Potassium Hydroxide, Calcium Chloride, Magnesium Chloride. Efflorescence- Efflorescence: Some substances lose water to the atmosphere when they are exposed to air, resulting in a weight loss. Copper(II) sulfate pentahydrate crystals are blue in color. Exposure to air causes the crystals to lose their water of crystallization. As a result of fluorescence, a white anhydrous copper (II) sulfate is formed.  Melting Point and Boiling Point Melting point (m.p.): the temperature at which a substance changes from a solid state to a liquid state. Pure crystalline materials have distinct (sharp)melting points. During melting, all the energy added to the substance is used as heat of fusion, and the temperature remains constant. or/ the temperature at which the forces between the crystals of a solid are broken. This leads to the transition from the crystalline state to the amorphous state (disordered state). For example, the melting point of water at 1 atmosphere is 0 °C (32 °F, 273.15 K). Also known as ice point. Boiling point (bp) :is the temperature at which the vapor pressure of a liquid equals atmospheric pressure. The boiling point of a substance can also be defined as the temperature at which it can change its state from a liquid to a gas at a given pressure. For example, the boiling point of H2O is 100 °C. Importance of m.p. It is a physical property that is used for identification. It is an important indicator of purity. The melting point makes it possible to characterize new compounds.  Factors affecting m.p & b.p 1. Molecular weight (M.Wt) or Size of the molecule 2. Impurities 3. Branching 4. Intermolecular interactions like Ionic , dipole- dipole attractions Van der Waal interactions, and H-bonding 1-Molecular weight (M.Wt) or Size of the molecule 4-Intermolecular interactions like Ionic , dipole-dipole attractions Van der Waal interactions H-bonding Alkane The longer the alkane gets (higher molecular weight), the more intermolecular forces are present (London Dispersion), and this increases the melting and boiling points. Van der Waals dispersion forces will be very small for a molecule like methane but will increase as the molecules get bigger. Therefore, the boiling points of the alkanes increase with molecular size.  A b.p of heptane is 98o,a difference in structure of one CH2 group for these compounds makes a difference in boiling point of 29o ; we would predict the boiling point of the next higher member, octane, to be 98o+29o=127o , which is close to the actual boiling point of 126o. Physical Properties of Some Alkanes Melting Point Boiling Point Physical State (at Molecular Name Formula Density (20°C)* (°C) (°C) 20°C) Methane CH4 –182 –164 0.668 g/L gas ethane C2H6 –183 –89 1.265 g/L gas propane C3H8 –190 –42 1.867 g/L gas butane C4H10 –138 –1 2.493 g/L gas pentane C5H12 –130 36 0.626 g/mL liquid hexane C6H14 –95 69 0.659 g/mL liquid heptane C7H16 -90 98 0.684 g/mL Liquid octane C8H18 –57 126 0.703 g/mL liquid decane C10H22 –30 174 0.730 g mL liquid  2- Impurities Impurities, even when present in small amounts, usually decrease the melting point and broaden the melting-point range. A wide melting point range (more than 5° C) usually indicates that the substance is impure; a narrow melting point range (0.5-2° C) usually indicates that the substance is pure. The more impurity is present, the lower the melting point. Finally, a minimum melting point is reached. The mixing ratio that results in the lowest possible melting point is known as the eutectic point. 3. Branching For isomers, the more branched the chain, the lower the boiling point tends to be. Van der Waals dispersion forces are smaller for shorter molecules and only operate over very short distances between one molecule and its neighbors. It is more difficult for short, fat molecules (with lots of branching) to lie as close together as long, thin molecules. Volatility increases with increased branching. Isomer M.P. (°C) b.P. (°C) Alkanes having same n-hexane −95.3 68.7 molecular weights, the 3-methylpentane −118.0 63.3 more highly branched 2-methylpentane alkane has a lower −153.7 60.3 boiling point. (isohexane) 2,3-dimethylbutane −128.6 58.0 2,2-dimethylbutane. -98 49.7 The boiling points of "straight chain" isomers and iso-alkanes isomers are compared to show how branching reduces surface area weakens intermolecular interactions  lowers the boiling point. The increase in m.p is less regular than the increase in b.p, because packing influences the melting point of a compound. Packing of the solid is a property that determines how well the individual molecules in a solid fit together in a crystal lattice. The tighter the crystal lattice, the more energy is required to break it and eventually melt the compound. Alkanes with an odd number of carbon atoms pack less tightly, which decreases their melting points. Thus, alkanes with an even number of carbon atoms have higher melting points than the alkanes with an odd number of carbon atoms. Polarity and solubility Polarity is a physical property of a compound that correlates with other physical properties such as melting and boiling points, solubility, and intermolecular interactions between molecules. Polarity is defined by the shape of the molecule and therefore by the arrangement of the electrical charges and whether they are symmetrical or asymmetrical. The number and types of polar and nonpolar covalent bonds present in a molecule are directly related to its polarity. In a few cases, a molecule having polar bonds, but in a symmetrical arrangement, may give rise to a nonpolar molecule, e.g. carbon dioxide (CO2). The term bond polarity is used to describe the sharing of electrons between atoms. A polar covalent bond exists when atoms with different electronegativities share electrons in a covalent bond. The electrons in a nonpolar covalent bond are shared equally between two atoms. A polar covalent bond is one in which one atom is more attracted to electrons than the other. The bond is an ionic bond when the relative attraction is strong.  The polarity of a bond is caused by the different electronegativities of the two atoms involved in bond formation. The greater the electronegativity difference between the bonded atoms, the greater the bond polarity. Thus, an atom's electronegativity is related to bond polarity. Water, for example, is a polar molecule, whereas cyclohexane is a nonpolar molecule.  More examples of polar and nonpolar molecules are shown in the following Table.  Solubility refers to the amount of a solute that can be dissolved in a specific solvent under specific conditions. The dissolved substance is the solute, and the dissolving fluid is the solvent; the two combine to form a solution. The process of dissolving is known as solvation or hydration when the solvent is water. The interaction of a dissolved species with the molecules of a solvent is known as solvation. The process of mixing solute (s) and solvent to form a solution is called dissolution. The stronger the intermolecular attractions (interactions) between solute and solvent, the more likely the solute will dissolve in a solvent. The rate of solution is a measurement of how quickly a solute dissolves in water or a specific solvent. It is also affected by particle size, stirring, temperature, and the amount of solid already dissolved. Temperature always affects solubility and an increasing temperature usually increases the solubility of most solids in a liquid solvent. The solubility of gases decreases with increase in temperature. The polarity of the solute and solvent also affects the solubility. The stronger the attractions between solute and solvent molecules, the greater the solubility. Thus the solubility of molecules can also be explained on the basis of the polarity of molecules. In general, like dissolves like; that is, materials with similar polarity are soluble in each other. Thus, polar solvent, for example, water (H2O), and nonpolar solvent, for example,benzene (C6H6), do not mix. The term miscible is used to describe two substances (usually liquids) that are soluble in each other. If they do not mix, as oil and water, they are said to be immiscible. For example, ethyl alcohol and water are miscible liquids as both are polar molecules, n- hexane and dodecane are also miscible in one another as both are nonpolar molecules, whereas chloroform (nonpolar) and water (polar) are immiscible. A polar solvent, such as H2O, has partial charges that can interact with the partial charges on a polar compound, such as ethyl alcohol. As nonpolar compounds have no net charge, polar solvents are not attracted to them. For example, alkanes are nonpolar molecules and are insoluble in polar solvents such as H2O, but are soluble in nonpolar solvents such as chloroform. Size of matters. Organic molecules with a branching carbon increases the solubility than a long-chain carbon, because branching reduces the size of the molecule and makes it easier to solvate. For example, isobutanol is more soluble in water than butanol.