Chapter Test Gen Chem Review PDF

Their particles are held close together by strong KINETIC MOLECULAR MODEL intermolecular forces, but not strong enough to keep them i...

Their particles are held close together by strong KINETIC MOLECULAR MODEL intermolecular forces, but not strong enough to keep them in a rigid position Explains the properties of solids and liquids in terms of the intermolecular forces of attraction and INTERMOLECULAR FORCES OF ATTRACTION the kinetic energy of the individual particles Intermolecular Forces Intramolecular Force Attractive forces between neighboring particles of Force inside/within a molecule one or more substances ○ Ionic bond (M + NM) Pulls the particles together ○ Covalent bond (Both NM) ○ Metallic bond (Both M) Kinetic Energy Keeps the particles at a distance and/or moving around Dependent on the temperature of the substance ↑ temperature, ↑ kinetic energy CHARACTERISTICS OF SOLIDS & LIQUIDS Chemical Bonding Properties of Solids Any of the interactions that account for the Definite shape and volume association of atoms into molecules, ions, crystals, Does not flow and other species Incompressible (because particles are tightly Holds together most molecules due to strong packed) (no space) attractive forces Expand when heated ○ To a lesser extent than liquids & gasses Intermolecular Force Denser (compact) than liquids Force between molecules ○ London dispersion force (LDF) Note: Solids assume a crystalline structure when they ○ Dipole-dipole interaction have a highly ordered packing arrangement. If not, they exist ○ Hydrogen bond as amorphous solids which have no definite form such as ○ Ion-dipole interaction rubber and wax. Note: Arranged from least to greatest. Particles of Solids Strongly attracted to each other Vibrate in fixed positions Vibrate faster when heated Intermolecular forces between their particles are stronger than those in liquids which keeps the solid rigid. Properties of Liquids Definite volume but no definite shape STRENGTH OF BONDS Flow and take the shape of container Intramolecular > Intermolecular Very difficult to compress INTRA is stronger than INTER Slightly expand when heated Denser than gasses Attraction Particles of Liquids Results from the interaction of two or more ions Weakly attracted to each other; break their forming a bond interaction easily Move more freely than those in solids; slide past one another ○ This makes liquid flow and take the shape of the container Move faster when heated Electronegativity Molecule has symmetry (structure) Ability of an atom to attract to itself an electron pair Example: shared with another atom in a chemical bond. ○ Ability to attract electrons to itself Helps to determine polarity POLARITY Comes from the uneven distribution of electrons among the various atoms in a molecule Polar → uneven distribution of electrons Nonpolar → electrons are evenly distributed Note: The arrow is always pointing towards the atom NONPOLAR with the stronger electronegativity. Molecules that are made up of ONE ELEMENT More electronegative atom → partial negative ○ Monatomic atom (noble gasses) charge Less electronegative atom → partial positive charge If the dipole moments point in opposite directions, they cancel out If the dipole moments point in the same direction, they can’t cancel out Dipole moments in a bent shape molecule cannot cancel out (ex: water) Gas is automatically nonpolar What if the molecule lacks symmetry? Is it always polar? → look at the electronegativity difference ○ Diatomic atoms **bigger value - smaller value = EN difference Example 1: Iodine monobromide I = 2.7 Br = 3.0 3.0 - 2.7 = 0.3 (nonpolar) Molecule that only contains carbon & hydrogen POLAR ○ CH4 (methane), C2H6 (ethane) If molecule has hydrogen bonding ○ H bonded to N, O, F Note: EN difference of carbon & hydrogen is small (< 0.5)  If molecule lacks symmetry TYPES OF IMF London Dispersion Forces (LDF) Present in all molecules regardless of their polarity Weakest type of IMF Only IMF present in nonpolar molecules Mas malayo, mas weak Exists between all atoms and molecules Molecule is polar since it has lone pairs and the ○ All molecules have LDF but since it is dipole moments pointing to O cannot cancel out weak, it is replaced by a stronger type of due to bent shape IMF Arise from the continuous movement of electrons in particles LDF is an attraction between a temporary dipole and an induced dipole ○ Nonpolar molecules have zero dipole moment because their electron density is uniform and symmetrical. Nevertheless, the electrons still have some freedom to move; therefore, at any instance, the molecule momentarily acquires a non-uniform electron density, resulting in a temporary dipole (also called instantaneous dipole). ○ This dipole can then induce dipoles in neighboring molecules. (induced dipoles) The size of the molecule can affect LDF ○ The bigger the molecule (molecule has greater surface area), the stronger the attraction ○ Two argon atoms have greater LDF than helium because they are bigger Temporary dipole, temporary attraction ○ Kapag may dumating na mas greater, mapapalitan Ionic Bond As long as there is a metal and nonmetal bonded Dipole-dipole Interaction together Present in all polar molecules All ionic bonds are extremely polar Between two polar molecules ○ Ionic bonds can dissociate while polar Polar substances have a permanent dipole do not moment due to difference in electronegativities of ○ Dissociate = split into other things such their component atoms as atoms, ions 2nd to the weakest type of IMF All polar molecules have unequal electron densities, resulting in a dipole ○ Dipole = a partial positive end and a partial negative end Partial positive charge of one molecule will be attracted to partial negative charge of neighboring molecule (opposites attract) Hydrogen Bond Hydrogen Bond Special type of dipole-dipole interaction but only Critical for DNA replication and genetic includes H directly bonded to N, O, and F information storage 5 to 10 times stronger than dipole-dipole It gives unique properties to water and other interactions organic material such as alcohol and medicine More electronegative atom (N, O, F) pulls the electrons toward itself and gains a partial negative Ion-Dipole Interaction charge. In turn, the hydrogen gains a partial It helps maintain the balance of ions necessary positive charge that attracts the partial negative for nerve function, muscle contraction, and charge of another molecule. overall cellular function Hydrogen bond is not a real chemical bond This interaction is critical for the dissolution of participated in by electrons salts and other ionic compounds ○ Dissolution - solute dissolves in solvent Ion-dipole Interactions → basta may ion and dipole Strongest type of IMF Summary: Presence of ions and dipole Presence of cation and anion Example: salt in water solvent ○ Na (+) will be attracted to O (-) ○ Cl (-) will be attracted to H (+) Activity: APPLICATIONS OF IMF London Dispersion Forces (LDF) Contribute to the stability of large biological molecules such as proteins and lipids Vast number of these weak forces collectively provide enough adhesive strength for insect to float on water Dipole-dipole Interaction The stability and volatility of certain fragrance molecules It contributes to the secondary and tertiary structures of proteins  Note: IMF is not just attraction forces, IMF and molecular PROPERTIES OF FLUIDS arrangement is related as it holds molecules together ++ Notes High Density Both liquid and gas molecules can flow due to the Density = bigat ng molecules spaces between their molecules Higher density than gas, meaning they are more Liquid molecules are closely packed together. As a massive per unit volume result, a liquid has definite volume as it will always occupy the same amount of space, regardless of Why liquids have high density: the shape of its container. 1. Hydrogen bonding ○ IMF of liquid is strong enough to hold 2. Bent shape the molecules and occupy the shape of the container but not enough to keep the Why is ice less dense? Lattice structure - bigger spaces liquid from not flowing between molecules ○ Since strong yung IMF ng water, Density anomaly – As water cools, it starts to definite ang volume niya expand and become less dense approaching freezing (why ice is less dense than water) Liquids can be described as thick or thin based Flowability on their viscosity Able to flow and be poured due to the mobility of Some liquids flow quickly, while others flow their particles, which can slide and move past more slowly. Why? each other FACTORS AFFECTING VISCOSITY Closely Packed 1. Molecular size and shape Particles of liquids are closely packed, but not Larger size, higher viscosity arranged in a regular pattern like in solids 2. IMF Higher IMF, higher viscosity Attraction 3. Chemical composition Attractive forces between liquid particles are Dissolved substance or impurities weaker than in solids, but stronger than in gasses Although water is a universal solvent, there are Kinetic Energy substances that cannot be mixed with water like oil Liquid particles have more kinetic energy than solid particles, allowing them to move and slide 1. Polarity and ionic nature – most of the compounds past each other while remaining relatively close like polar molecules dissolve in water but when it From the heat comes to nonpolar substances like oil and many organic substance do not dissolve in water well OTHER PROPERTIES OF LIQUIDS 2. Hydrophobic substances – afraid of water, does not interact with water 3. Size and structure Surface Tension Acts like a stretch rubber membrane Property of liquid to resist an external force and GENERAL PROPERTIES OF LIQUIDS thus assume a lesser surface area Attributed to strong attractive and cohesive Indefinite Shape forces between and among the molecules, No fixed shape particularly at the surface of the liquid ○ Spaces between molecules Discusses concept of adhesion and cohesion Takes the shape of container, allowing them to be Its strength has direct relationship with the poured or transferred strength of IMF (↑IMF, ↑ST) Strong cohesive force explains why spherical Definite Volume water droplets form Have fixed volume, meaning they cannot be easily Allow water to hold a heavier paper clip or allows compressed or expanded, and take up space small insects to walk on its surface Reasons: 1. IMF holds and maintains consistent volume 2. Molecular arrangement – since it’s close to each other, it prevents the liquid from expanding indefinitely, giving its definite volume 3. Fluid dynamics – volume remains the same as long as the temp and pressure do not change  What’s the difference between buoyancy and surface tension? Buoyancy Upward force exerted by liquid/gas on an object, force is greater on the bottom of the object than the force on top ○ Galing sa baba yung force Ability of an object to float on top of water Surface tension B - concave meniscus, capillary attraction Force acting on the surface of the liquid C - convex meniscus, capillary repulsion Behaves like elastic sheets – because of cohesive force Viscosity Net inward forces cause water to minimize the Ability to resist flow area and causes the molecules to contract and Thickness or thinness of liquid resist to be stretched since there is no attractive It is related to the ease with which the molecules forces acting on the surface above can move past each other The stronger the intermolecular forces, the more viscous the substance is Cohesive Forces Long-chained substances like oil have greater Attractive forces between molecules of the same intermolecular forces because there are more type atoms that can attract one another Molecules attracted with the same molecules Honey is viscous because of hydrogen bonding (water - water) (strong IMF) The stronger the interaction between particles, the more rigid (solid) they will be at room temperature Factors affecting viscosity: 1. Strength of IMF Adhesive Forces a. Greater strength of IMF, higher viscosity Attractive forces between molecules of different 2. Molecular size type a. Bigger the molecular size, higher Molecules attracted with different molecules viscosity 3. Temperature a. Higher temp, mas mabilis na flow (lower viscosity) Temperature Concept of boiling point and melting point of a substance The greater the IMF, the higher the boiling and melting point The longer the hydrocarbon, the lower the boiling B - greater adhesive property and melting point temperature C - greater cohesive property Boiling point Capillary Action Temp at which its vapor pressure = external or Force that helps liquids to climb against gravity on atmospheric pressure the surface of something else (adhesive) Increasing the temperature of a liquid raises the Capillary attraction - greater adhesion kinetic energy of its molecules until such point Capillary repulsion - greater cohesion where the energy of the particle movement Its strength has direct relationship with the exceeds the intermolecular forces that hold them strength of IMF together Temp at which a liquid boils under an atmospheric pressure of 760 mm Hg (1 atm) is referred to as normal boiling point Normal BP of water = 100°C Greater IMF, higher energy needed to increase kinetic energy of molecules to break these forces ○ This is why water has higher boiling point than hexane ○ Hydrogen bond - water; LDF - hexane Molar Heat of Vaporization & Condensation About absorbing or releasing heat Water escapes to form another state of matter Vaporization - absorbs heat, liquid to gas If you want to get water to change from liquid to gas, you need to give it enough energy to break the "bonds" holding the water molecules together in the liquid form. This energy is the molar heat of vaporization. Condensation - releases heat, solid to liquid, gas to liquid When steam (gas) cools down and becomes liquid water, it releases the same amount of energy it took to turn the liquid into gas in the first place. This released energy is the molar heat of condensation. Molar Heat of Vaporization Amount of heat required to vaporize one mole of a substance at its boiling point PHASE DIAGRAM The application of heat disrupts the IMF of liquid molecules and allows them to vaporize Endothermic Reaction ↑ Boiling point, ↑ Molar heat of vaporization Absorbs heat Higher surface area, higher BP and molar heat of Endo - inside, thermic - heat vaporization System absorbs heat from surroundings Greater IMF, higher BP and molar heat of vaporization Exothermic Reaction Releases heat Note: Strong IMF requires more energy to overcome these Exo - outside forces leading to higher boiling point (more energy kasi mas System releases heat to surroundings mahirap i-break down yung bond) ++ Vapor Pressure Pressure exerted by its vapor when in equilibrium with its liquid or solid This means that when a liquid or solid substance is made to evaporate in a closed container, the gas exerts a pressure above the liquid Greater IMF, lower vapor pressure ○ Because particles will have difficulty escaping as a gas If the temperature is enough, solid becomes gas (sublimation) or gas becomes solid (deposition) directly (skips liquid phase) Phase Changes ○ Triple point Requires the input or removal of energy or change Happens when temp and in pressure pressure are in equilibrium Temperature does not change (constant) but All three phases coexist amount of energy does ○ Single-phase point Transformation of matter from one state to another Solid, liquid, gas that involves the absorption or release of heat HEATING/COOLING CURVE Phase Diagram A graphical representation of the physical states of a substance under different conditions of Focuses on temperature changes over time during temperature and pressure. heating or cooling Graphical representation of the Shows how temperature remains constant during pressure-temperature relationships that apply to phase transitions the equilibria between the phases of a substance Depicts specific heat and phase transition points Useful in determining the combination of (melting/freezing, boiling/condensation). temperature and pressure at which a substance will exist as a solid, liquid, or gas Notes: Focuses on the equilibrium states of matter Phase changes occur with increased temperature Does not involve time or heat addition/removal. Example of sublimation: dry ice Illustrates the conditions under which a substance exists as a solid, liquid, or gas, including critical points and triple points. Components: Area Represent the phases of a matter Single phase of matter exists Solid: left most area Liquid: upper middle area Gas: right most area Heating curve - endothermic Cooling curve - exothermic Lines Represent the phase changes of a matter Two phases of matter exist Boundary between the different phases 1st line from the bottom: sublimation or deposition 2nd line (left): melting or freezing 3rd line (right): evaporation or condensation Points Represent a specific set of conditions under which a particular phase or phase change of a substance occurs ○ Critical point Can’t escape gas state You can’t differentiate between liquid and gas ○ Phase-boundary point