IMF and Liquids Notes PDF

INTERMOLECULAR FORCES AND LIQUIDS  OBJECTIVES 1) Explain the properties of Liquids and solids in connection to Kinetic Molecular Theory; 2) Differentiate the types of intermolecular forces; 3) Describe the different properties of liquids and explain the effect of...

INTERMOLECULAR FORCES AND LIQUIDS  OBJECTIVES 1) Explain the properties of Liquids and solids in connection to Kinetic Molecular Theory; 2) Differentiate the types of intermolecular forces; 3) Describe the different properties of liquids and explain the effect of IMF on these properties; and 4) Recognize the importance of water’s properties and Intermolecular Forces in biological systems.  INTERMOLECULAR FORCES AND LIQUIDS  SOLID, LIQUID, AND GAS Liquids and solids are often referred to as condensed phases because the particles are very close together. KINETIC MOLECULAR THEORY KEY CONCEPTS Matter is made of particles that are constantly in motion. These particles hold kinetic energy and move around in random directions. There is a space between particles. The amount of space in between particles is related to the substance’s state of matter. KINETIC MOLECULAR THEORY Microscopic Properties of atoms/molecules and how they interact leads to the Macroscopic Properties of the substance. This also explains the temporary attractions formed between molecules.  PHASE CHANGES Phase changes happen when the temperature of the substance changes sufficiently. There are attractive forces in between particles that create temporary attractions. These are called INTERMOLECULAR FORCES. INTERMOLECULAR AND INTRAMOLECULAR FORCES INTRAMOLECULAR FORCES Intramolecular forces are the forces that hold atoms together within a molecule. Chemical bonds are considered to be intramolecular bonds. Determine Chemical Properties INTERMOLECULAR FORCES Intermolecular forces exist between molecules. Intermolecular forces determine the physical properties of molecules like boiling point, melting point, density, enthalpies of fusion, and vaporization. TYPES OF INTERMOLECULAR FORCES TYPES OF INTERMOLECULAR FORCES  RELATIVE STRENGTH OF INTERMOLECULAR FORCES Type of Intermolecular Occurs between Relative Strength Forces London Dispersion Forces Temporary or induced dipoles Weakest Partially oppositely charge ions Dipole-dipole interaction Strong ( δ+, δ−) Stronger than dipole-dipole Hydrogen bonding H atom and O, N or F atom interaction Ionic compounds and polar Ion-dipole interaction Strongest molecules  TYPES OF INTERMOLECULAR FORCES Type of compound Intermolecular forces present Ionic Compounds Ion to polar attraction, Dispersion forces Covalent compounds containing hydrogen Hydrogen bonding, Dispersion forces bonds (with O, N and F) Polar covalent compounds Dipole-dipole interaction, Dispersion Forces Nonpolar covalent compounds Dispersion forces Electronegativity and Intermolecular Forces Electronegativity is, in essence, how strongly an atom will pull a pair of electrons towards itself in a covalent bond. Electronegativity increases as we move towards the top right-hand corner of the periodic table (not including noble gases). The most electronegative element is fluorine. Greater electronegativity difference leads to stronger intermolecular forces  TYPES OF INTERMOLECULAR FORCES Let’s try to identify the different kinds of intermolecular forces present in some molecules. 1. H₂S Dispersion Forces Dipole-dipole interaction  TYPES OF INTERMOLECULAR FORCES Let’s try to identify the different kinds of intermolecular forces present in some molecules. 2. CH₃OH Dispersion Forces Dipole-dipole interaction Hydrogen bonding  TYPES OF INTERMOLECULAR FORCES Let’s try to identify the different kinds of intermolecular forces present in some molecules. 3. C₂H₆ Dispersion Forces  EFFECTS OF IMF TO THE PROPERTIES OF LIQUIDS * Surface Tension * Viscosity * Boiling Point and Melting Point * Vapor Pressure EFFECTS OF IMF ON THE PROPERTIES OF LIQUIDS  EFFECTS OF INTERMOLECULAR FORCES ON THE PROPERTIES OF LIQUIDS Relative order of boiling Relative order Intermolecular Relative order of Relative order of Type of compound point and of Surface forces present Viscosity Vapour pressure melting Tension points Ion to ion attraction Ionic Compounds between ions, 1 (highest) 1 1 4 dispersion forces Covalent compounds Hydrogen bonds, 2 2 2 3 containing hydrogen dispersion forces Dipole-dipole Polar covalent interaction, 3 3 3 2 compounds dispersion forces Nonpolar covalent Dispersion forces 4 4 4 1 compounds STRUCTURE AND PROPERTIES OF WATER In each water molecule, the nucleus of the oxygen atom (with 8 positively charged protons) attracts electrons much more strongly than the hydrogen nuclei (with only one positively charged proton). STRUCTURE AND PROPERTIES OF WATER Making water molecules POLAR (partial negative and positive). This nature also creates a strong attraction between water molecules, which is HYDROGEN BONDING.  PROPERTIES OF WATER High Surface Tension High Boiling/Melting Point High Specific Heat ( amount of heat to raise or lower the temperature of 1 gram of substance by 1 degree Celsius) High Heat of Vaporization (heat required to vaporize a liquid)  PROPERTIES OF WATER These properties of water are possible due to its molecular shape, polar nature, and ability to form hydrogen bonding. These properties are important to biological systems.  WATER AS A THERMAL BUFFER * ON CELLS/BODY - Water in a cell can absorb much heat with little temperature change. - Homeostasis: Water helps maintain a stable internal temperature despite external temperature fluctuations (crucial for enzyme function and metabolic processes). - Sweating and Transpiration  WATER AS A THERMAL BUFFER * ON OUR OCEANS - Water in the ocean acts as a thermal buffer for the earth, resisting temperature change and creating a hospitable environment for life.  WATER AS A UNIVERSAL SOLVENT Transport of Nutrients and Wastes: Water facilitates the movement of nutrients, gases, and wastes in and out of cells and throughout the organism. Chemical Reactions: Many biochemical reactions occur in aqueous solutions, where water helps to dissolve reactants and products, making them available for interactions.  COHESION AND ADHESION Capillary Action: In plants, water’s cohesion and adhesion allow it to move against gravity through xylem vessels, transporting nutrients and water from roots to leaves. Formation of Meniscus: In biological systems, water's behavior at surfaces can affect the behavior of liquids in small spaces, influencing processes like fluid transport in microenvironments.  HYDRATION SHELLS Ion Solubility: Water’s ability to surround ions allows them to dissolve in the cytoplasm and extracellular fluids, where they can participate in biochemical reactions and maintain electrochemical gradients. Molecular Interactions: Hydration shells influence how molecules interact with each other, affecting processes such as enzyme-substrate binding and signal transduction.  PH AND BUFFERING Buffer Systems: In biological systems, water participates in buffer systems that help maintain a stable pH, which is necessary for the proper functioning of enzymes and metabolic pathways. Acid-Base Reactions: Water itself can dissociate into hydrogen and hydroxide ions, and this dissociation is involved in many biological acid-base reactions. SUMMARY  SUMMARY Why do liquids and solids differ in properties? Explain in connection to KMT. What are the types of Intermolecular Forces? How are they different from each other? What are the properties of liquids? How are these affected by IMFs? How do water’s properties and IMF affect biological systems? END