General Chemistry II - Senior High School (STEM) PDF

GENERAL CHEMISTRY II  General Chemistry 2 – Senior High School (STEM) EQ: Why do solids and liquids behave differently? ◾ The Kinetic Molecular Theory explains the properties of solids and liquids in terms of intermolecular forces of attraction and the kinetic ene...

GENERAL CHEMISTRY II  General Chemistry 2 – Senior High School (STEM) EQ: Why do solids and liquids behave differently? ◾ The Kinetic Molecular Theory explains the properties of solids and liquids in terms of intermolecular forces of attraction and the kinetic energy of the individual particles. 1.All matter is made up of tiny particles. 2. These are particles are in constant 3. The motion. speed of is proportional particle to temperature. temperature Increased greater means 4. speed. Solids, liquids, and gases differ in distances between particles, in the freedom of motion of particles, and in the extent to which the particles interact. a. Compare the distances among molecules in the gas, liquid and solid and rank the phases in increasing distance between particles. b. Describe the characteristic movement of the particles of gas, liquid and solid. c. How are the molecules of gas, liquid and solid arranged? d. Arrange the three phases of matter in order of increasing volume of empty space between its molecules.  General Chemistry 2 – Senior High School (STEM) EQ: How is intermolecular forces defined by nature of particles? ◾ INTERMOLECULAR FORCES are attractive forces between molecules or particles in the solid or liquid states. ◾ INTERMOLECULAR FORCES (IMF) are relatively weaker than the forces within the molecules forming bonds (intramolecular forces) ◾ IntramolecularForces hold atoms together in a molecule. ◾ The intermolecular forces of attraction in a pure substance are collectively known as van der Waals forces. 1. Dipole-dipole 2. Hydrogen bonding 3. Ion-dipole 4. London dispersion 5. Dipole-induced dipole force ◾ Dipole-dipole forces exist between polar molecules. One end of a dipole attracts the oppositely charged end of the other dipole. ◾ It is a special and very strong type of dipole – dipole force that exists between a hydrogen atom bound to a small and highly electronegative non-metal atom. Hydrogen ◾ containingH bond and occurs any in highl polar y molecules ofelectronegative elements, in Nitrogen, Fluorine, and particular Oxygen. ◾ It acts between an ion (either positive or negative) and a polar molecule. ◾ This explains the solubility of ionic compounds in water, which is polar molecule.  ◾ The ions and the oppositely charged ends of the polar water molecules overcome the attraction between ions themselves. Each ion becomes separated and water molecules cluster around it. ◾ It is the weakest type of intermolecular force. ◾ When two non-polar molecules approach each other, an instantaneous dipole moment forms. ◾ This force is sometimes called an induced dipole-induced dipole attraction. ◾ Interaction between Polar and non-polar molecules. What type of intermolecular force will act in the following substances? Justify your answer. 1. sulfur dioxide (SO2) 2. nitrogen gas (N2) 3. hydrogen fluoride (HF) 4. carbon dioxide (CO2) 5. neon gas (Ne) 6. magnesium chloride (MgCl2) dissolved in water (H2O)  General Chemistry 2 – Senior High School (STEM) EQ: How do intermolecular forces influence the properties of liquids? ◾ Liquids do not have a simple or structure, regular of their many but properties ca qualitatively n be by viewing them explained at the particulate level.  Surfac e Tensio n Capilla Viscosi ry ty Action General Propert ies of Heat of Liquids r Vapou Vaporizati Pressur on e Boiling Point ◾ It is the measure of the elastic force in the surface of a liquid. ◾ It is the amount of energy required to stretch or increase the surface of a liquid by a unit area. ◾ It is manifested as some sort of skin on the surface of a liquid or in a drop of liquid. ◾ Surface tension allows needles and paper clips to float in water if placed carefully on the surface. It also explains why drop of water are spherical in shaped ◾ These intermolecular forces tend to pull the molecules into the liquid and cause the surface to tighten like an elastic film or “skin”. ◾ Molecules within a liquid are pulled in all directions by intermolecular forces. ◾ Molecules at the surface sideway are by pulled downward s and other away from the molecul not surface es, upward ◾ The liquids that have strong Intermolecular forces also have high surface tension. ◾ Capillary action is the tendency of a liquid to rise in narrow tubes or be drawn into small openings such as those between grains of a rock. ◾ Capillary action, also known as capillarity, is a result of intermolecular attraction between the liquid and solid materials. ◾ Capillary action is shown by water rising spontaneously in capillary tubes. A thin film of water adheres to the wall of the glass tube as water molecules are attracted to atoms making up the glass (SiO2). Examples of Capillary action Tears flowing through tear ducts, water rising in a straw or glass tube defying gravity, and water passing through a cloth towel These represent examples of capillary action. ◾ Two types of forces are involved in capillary action: ◾ Cohesion is the intermolecular attraction between like molecules (the liquid molecules). ◾ Adhesion is an attraction between unlike molecules (such as those in water and in the particles that make up the glass tube). ◾ When the cohesive forces between the liquid molecules are greater than the adhesive forces between the liquid and the walls of the container, the surface of the liquid is convex. ◾ When the cohesive forces between the liquid molecules are lesser than the adhesive forces between the liquid and the walls of the container, the surface of the liquid is concave. A concave meniscus, which is what you normally will see, occurs when the molecules of the liquid are attracted to those of the container. This occurs with water and a glass tube. A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container, as with mercury and glass ◾ It is defined as the resistance of a liquid to flow. ◾ It is loosely referred to as the thickness or thinness of a liquid. ◾ Syrup and oil flow more slowly than water and are thus described as more viscous. ◾ The of viscosity depends liqu on intermolecular id attraction. thei ◾ The r th e intermolecular stronger force, isthethe higher liquid’s viscosity ◾ Long-chained substances oil like great intermolecu have er because lar there force atoms are that can s attract one another, mor contributing to e the substance’s total attractive forces. ◾ a Honey concentrated of ,highly viscoussugar, becauseis solutio of the hydrog bondin also that ng enforms as a of numerous- result OH the groups of sugar molecule. ◾ It is the pressure exerted by its vapor when in equilibrium with liquid or solid. Example: ◾ When liquid or solid substance is made to evaporate in a closed container, the gas exerts a pressure above the liquid. ◾ with stro Substance relatively ng low pressure s because forces will vapor difficulty intermolec the escaping haveas a gas. particles will Example: ular have 1. Water (H2O), (Hydrogen Bonding) has vapor pressure of 0.03 atm. 1. Ethyl Ether (C4H10O), dipole- dipole & London Force ) has vapor pressure at 0.68 atm. ◾ The point of a liquid is temperaturethe boiling at which its vapor pressure is equal to the external or atmospheric pressure. ◾ Increasing the temperature of a liquid raises the kinetic energy of its molecules, until such point where the energy of the particle movement exceeds the ◾ The liquid molecules then transform to gas and are seen as bubbles that rises to the surface of the liquids and escape to the atmosphere. ◾ Then temperature at which a liquid boils under 1 atmospheric pressure (1atm) is referred to as its normal boiling point. ◾ At higher altitude, the atmospheric pressure is lower, hence, the boiling point will subsequently decrease. ◾ The greater intermolecular force, the higher the energy needed to increase the kinetic energy of the molecules to break these forces. ◾ MolarHeatof vaporization ( is Hvap amountof the heat required to vaporize one mole of substance ) at its boiling point. ◾ The application of heat disrupts intermolecular forces the of liquid attraction molecules and allows them to the of vaporize. ◾ Boiling point generally increases as molar heat of vaporization increases. ◾ The Hvap is also determined by the strength of intermolecular forces between molecules. ◾ At room temperature, pure water is a colorless, odorless and tasteless liquid. ◾ It turns to ice, its solid form at 00 C and 1 atm. ◾ At 1000 C, it become gas, 1. Water is a good solvent. 2. Water has a high specific heat. Specific heat is the amount of heat or energy needed to raise the temperature of one gram of a substance by 1o C. 3. The boiling point of water unusually high. 4. Solid water is less dense, and in fact floats on liquid water. ◾ Unlike all other liquids, the molecules in solid water are actually farther apart than they are in liquid water. ◾ When solid water forms, the hydrogen bonds result in a very open structure with unoccupied spaces, causing the solid to occupy a larger volume than the liquid. ◾ This makes ice less dense than liquid water, causing ice to float on water.  General Chemistry 2 – Senior High School (STEM) EQ: How do you describe solids? ◾ Solid can be classified as crystalline or amorphous based on the arrangement of their particles. ◾ Crystalline solids have highly regular arrangement of particles, while amorphous solids have considerable disorder in their structure. ◾ Amorphous solids, such a are rapidl glass, formed constituent y that particles itsdo not have time to align or organize into a more crystalline lattice. ◾ CrystallineSolids have well- defined crystal lattice. A lattice is a three- points dimensional designating system the of positions components (ions, of atoms, or the molecules) that makeup a crystal. ◾A unitcell is the smallest repeating unit of lattice.  TYPES COMPONEN TYPE OF TYPICAL PROPERTIES EXAMPLES TS THAT INTERACTION OCCUPY BETWEEEN THE COMPONENTS LATTICE OF LATTICE POINTS IONIC Ions Ionic Hard, high melting NaCl point; insulating as solid but conducting when dissolved. MOLECULA Discret Dipole-dipole Soft; low melting Ice, dry ice R e or London point molecul dispersion es METALLIC Metal atoms Delocalized Wide range of Silver, covalent hardness and Iron, melting points Brass NETWORK Nonmet Directional Hard, high melting Diamond al covalent point atoms  General Chemistry 2 – Senior High School (STEM) EQ. When does equilibrium exist between the phases of a substance? ◾ Phase Changes are transformations of matter from one physical state to another. ◾ They occur when energy is added or removed from a substance. ◾ They are characterized by changes in molecular order; molecules in the solid phase have the greatest order, while those in the gas phase have the greatest randomness or disorder. ◾ What changes in molecular order occur during phase changes? ◾ How does a change in energy affect phase changes? ◾ How does a change in energy affect phase changes? ◾ How can this effect be achieved using CO2 or dry ice? Carbon dioxide cannot exist as a liquid at atmospheric pressure, the dry ice sublimates and instantly produces a gas, condensing water vapor, and creating a thick white fog. ◾ What does LPG stand for? How can a gas be liquefied? ◾ What conditions are needed to convert a gas into a liquid? ◾ Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), are flammable mixtures of hydrocarbon gases. ◾ It is used as fuel in heating appliances, cooking equipment, ◾ It is a graphical representation of the physical states of a substance under different conditions of temperature and pressure. ◾ It gives the possible combinations of pressure and temperature at which certain physical state or states a substance would be observed. ◾ Phase diagrams are plots of pressure (usually in atmospheres) versus temperature (usually in degrees Celsius or Kelvin). 1. Three Areas (Solid, Liquid, Gas) ◾ The three areas are marked solid, liquid, and vapor. Under a set of conditions in the diagram, a substance can exist in a solid, liquid, or vapor (gas) phase. ◾ The lines that serve as boundaries between physical states represent the combinations of pressures and temperatures at which two phases can exist in equilibrium. ◾ In other words, these lines define phase change points. ◾ The green line divides the solid and liquid phases, and represents melting (solid to liquid) and freezing (liquid to solid) points. ◾ Melting (or freezing) curve – the curve on a phase diagram which represents the transition between liquid and solid states. ◾ It shows the effect of pressure on the melting point of the solid. Anywhere on this line, there is equilibrium between the solid and the liquid. ◾ The blue line divides the liquid and gas phases, and represents vaporization (liquid to gas) and condensation (gas to liquid) points. ◾ The on a phase diagram represents which curve the transition between gaseous and liquid states. It shows the effect of pressure on the boiling point of the liquid. ◾ Anywhere along this line, there will be equilibrium between the liquid and the vapor. ◾ The red line divides the solid and gas phases, and represents sublimation (solid to gas) and deposition (gas to solid) points. ◾ The curve on a phase diagram which represents the transition between gaseous and solid states. ◾ It represents the effect of increased temperature on a solid at a very low constant pressure, lower than the triple point. ◾ The triple point is the combination of pressure and temperature at which all three phases of matter are at equilibrium. ◾ It is the point on a phase diagram at which the three states of matter coexist. The lines that represent the conditions of solid-liquid, liquid- vapor, and solid-vapor ◾ The critical point terminates the liquid/gas phase line. It is the set of temperature and pressure on a phase diagram where the liquid and gaseous phases of a substance merge together into a single phase. ◾ Beyond the temperature of the critical point, the merged single phase is known as a Constructing a Phase Diagram Visualize a substance with the following points on the phase diagram: a triple point at 0.05 atm and 150 K; a normal melting point at 175 K; a normal boiling point at 350 K; and a critical point at 2.0 atm and 450 K. The solid liquid line is “normal” (meaning positive sloping). For this, complete the following: 1. Roughly sketch the phase diagram, using units of atmosphere and Kelvin. Label the area 1, 2, and 3, and points T and C on the diagram. 2. Describe what one would see at pressures and temperatures above 2.0 atm and 450 K. 3. Describe the phase changes from 50 K to 250 K at 1.5 atm. 4. What exists in a system that is at 1 atm and 350 K?