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KINETIC-MOLECULAR-MODELS-OF-LIQUIDS-AND-SOLIDS.pptx
- 1. KINETIC MOLECULAR MODELS OFLIQUIDS AND SOLIDS CAROLLE P. USITA
- 2. Content: • Intermolecular forcesof attraction • Properties of liquids • Physical and chemical properties of water • Types and properties of solids • Phase changes • Phase diagram 2
- 3. INTERMOLECULAR FORCES OF ATTRACTION Theintermolecular forces of attraction pertain to forces that hold individual particles such as atoms, molecules, or ions together. The strength of the intermolecular forces of attraction is dependent on the arrangement of the particles, the proximity of particles relative to one another, and the nature of the interacting particles. The intermolecular forces of attraction influence the resulting properties of solids, liquids, and gases. In solids, for example, the intermolecular forces of attraction directly affect its melting point and heat of fusion. 3
- 4. The intramolecular forcesof attraction, on the other hand, are those responsible for interactions within a molecule, such as covalent and ionic bonds. One example would be the different amino acids present in a certain protein. The functional groups in each amino acid interact with one another, enabling the protein to have a folded structure. Generally, intramolecular forces of attraction are stronger than intermolecular attractions. 4 Intramolecular forces of attraction
- 5. Intermolecular forces explainthe physical properties of substances. Similar to magnets, the stronger the intermolecular forces of attraction, the more difficult it is to pull molecules away from each other. 5
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- 8. 1. London dispersionforce Named after the German-born physicist Fritz London, this is the weakest among the intermolecular forces. This dispersion force is caused by polarization, or the distortion of the electron cloud brought about by the presence of a highly charged particle. In this case, the electron cloud of one atom is attracted to the positively charged nucleus of another atom. 8
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- 10. London dispersion isthe temporary attraction between dipoles, which occur among all types of molecules. It also determines the physical properties of nonpolar substances. 10
- 11. The number ofelectrons in an atom affects the polarizability of the atom. This is due to the number of electrons affecting the size of the electron cloud. As a result, the larger the electron cloud, the higher the chances of the atom getting attracted by a positively charged particle. This results in the formation of temporary dipoles, wherein one end of the atom is partially positive and the other end is partially negative. To summarize, the London dispersion force happens when one molecule with a temporary dipole exerts a weak attractive force on another molecule. 11
- 12. 2. Dipole-dipole Interaction Thisis an intermolecular force of attraction that occurs between partially positive and partially negative ends. This interaction is observed in polar covalent molecules such as amino acids, wherein the electrons are shared both by oxygen and carbon atoms. However, due to the electronegativity of the oxygen atom, the oxygen atom assumes a partially negative charge, whereas the carbon atom assumes a partially positive charge. 12
- 14. The dipole-dipole interactionoccurs due to the attraction between the opposite, partially charged molecules. The more polar the molecules are, the stronger the dipole dipole interaction. 14
- 15. 3. Ion-dipole interaction Thisarises from the interaction between an ion and a polar molecule. If the molecule is an anion (negatively charged ion), it will be attracted to the partially positive end of the polar molecule; however, if the molecule is a cation (positively charged ion), it will be attracted to the partially negative end of the polar molecule. 15
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- 17. 4. Hydrogen bond Ahydrogen bond is a special kind of dipole-dipole interaction, which is formed when hydrogen bonds with fluorine, oxygen, or nitrogen. In a hydrogen bond, the partially positive end of the hydrogen atom is attracted to the partially negative end of fluorine, oxygen, or nitrogen. Generally, hydrogen bonds are still weaker than ionic or covalent bonds, but they are the strongest intermolecular force of attraction (when the hydrogen bond is present between two atoms of two different molecules). 17
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- 20. Substance Evaluate its composition andstructure Is it polar? Are ions present? Is hydrogen bonding involved? Hydrogen bonding Is both ionic and polar? Covalent bonding Dipole-dipole forces Ionic bonding London dispersion force NO NO YES YES NO YES YES NO
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- 22. 1. Viscosity This propertyrefers to the measure of a liquid's resistance to flow. The viscosity of a liquid is strongly dependent on the strength of the intermolecular forces in play. Highly viscous liquids are those exhibiting the strongest intermolecular forces. For example, glycerol, a highly viscous 22
- 23. The actual viscositiesof liquids may vary, but they generally increase when stronger intermolecular forces are present. 23
- 24. 2. Surface Tension Thisrefers to the amount of resistance needed to increase the surface area of liquids. 24
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- 26. The higher thesurface tension is, the stronger the intermolecular force. This can be observed in hydrogen bonding in water. 26
- 27. 3. Vapor Pressure Vaporizationis the transformation of a substance from a liquid to a gas. Vaporization is an endothermic process as it requires absorption of energy to break the intermolecular forces of attraction in a liquid. 27
- 28. The large heatof vaporization of water helps in regulating the temperature of Earth's surface from the energy of the sun. 28
- 29. 4. Boiling Point Aliquid boils when its vapor pressure is equal to the prevailing atmospheric pressure. The normal boiling point of any liquid is directly influenced by the existing intermolecular forces of attraction. So if a stronger intermolecular force of attraction is in place, the liquid will have a relatively higher boiling point. 29
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- 33. Water is thechemical substance with chemical formula H2O, one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. 33
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- 37. Freezing A phase transitionwhere a liquid turns into a solid when its temperature is lowered below its freezing point. 37
- 38. Melting defined as thepoint at which materials changes from a solid to a liquid. The temperature at which solid changes its state to liquid at atmospheric pressure is called the melting point of that liquid. This is the point at which both liquid and solid phase exists at equilibrium. 38
- 39. Vaporization conversion of asubstance from the liquid or solid phase into the gaseous (vapour) phase. If conditions allow the formation of vapour bubbles within a liquid, the vaporization process is called boiling. Direct conversion from solid to vapour is called sublimation. 39
- 40. Condensation change of waterfrom its gaseous form (water vapor) into liquid water. 40
- 41. Sublimation The process inwhich solids directly change to gases is known as sublimation. This occurs when solids absorb enough energy to completely overcome the forces of attraction between them. Dry ice is an example of solids that undergo sublimation. 41
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