Presentation on theme: "Recall from Ionic Bonding…"— Presentation transcript:
1 Recall from Ionic Bonding… The partially positive hydrogens of the water molecules attract and pull away the negative chloride ions.The partially negative oxygens of the water molecules attract and pull away the positive sodium ions.Big Question: For one substance to dissolve another, what is required of both substances?
3 Intermolecular Forces forces between moleculesIntermolecular forces are attractions between molecules.Intermolecular forces are weaker than covalent or ionic bonds.
4 Intermolecular Forces Are caused by molecule polarity
5 Intermolecular Forces Determine whether a molecule is a gas, liquid, or solid at a given temperature.Think-Pair-ShareHow do you think intermolecular forces may determine the state of matter of a substance?
6 Intermolecular Forces Determine the ability of substances to dissolve one another.
7 Why don’t oil and water mix? Oil is nonpolar.Water is polar.
8 Intermolecular Forces Determine the ability of substances to dissolve one another.“Like dissolves like”Polar molecules dissolve polar molecules and ionic compoundsNonpolar molecules dissolve nonpolar molecules only
9 3 Types of Intermolecular Forces Listed in order of increasing strength:London dispersion forcesDipole-dipole interactionsHydrogen bondingNote: London dispersion forces and dipole-dipole interactions are collectively calledvan der Waals forces.
10 London Dispersion Forces Occur in ALL moleculesThe weakest of molecular interactionsCaused by the motion of electronsElectrons are in constant motion. At times, more electrons can be on one side of a molecule than another.What do you think happens to the molecule when electrons do this?The strength of dispersion forces increases as the number of electrons in a molecule increases.
15 London Dispersion Forces A single dispersion force is very weak by itself.However, when millions and millions of dispersion forces happen in a substance the force dispersion force is a significant intermolecular force.The strength of dispersion forces increases as the number of electrons in a molecule increases.
16 At ordinary room temperature and pressure: Fluorine and Chlorine = gases Bromine = liquid Iodine = solidWhy do you think this is? Explain in terms of dispersion forces.
17 London Dispersion Forces Occur in ALL molecules- polar and nonpolarThe only type of intermolecular force found in nonpolar molecules
18 Dipole-Dipole ForcesThe + and – ends of polar molecules attract one another.Dipole-dipole interactions are similar to but much weaker than ionic bonds.
19 Do you think Dipole-Dipole Forces will occur in nonpolar molecules? The slightly negative region of a polar molecule is weakly attracted to the slightly positive region of another polar molecule.Do you think Dipole-Dipole Forces will occur in nonpolar molecules?
20 Hydrogen Bonding Strongest type of intermolecular force Hydrogen bonding always involves hydrogenHydrogen is bonded to a very electronegative atom (oxygen, nitrogen, or fluorine)A specialized type of dipole-dipole force
21 Hydrogen BondingA single hydrogen bond has about 5 percent of the strength of the average covalent bond.They are extremely important in determining the properties of water and biological molecules.
22 The “Glue” Between Molecules Dispersion forceDipole-dipole forceHydrogen bondingweakestIM forceCopy this slide on the back of Do NowstrongestIM force
23 Determine the strongest type of IM Force in: Dihydrogen sulfide Sulfur monoxide Dinitrogen dihydride
24 How do intermolecular forces influence the physical properties of substances? The diversity of physical properties among covalent compounds is mainly because of widely varying intermolecular attractions.
25 Properties of Substances ViscosityThe ability of a substance to resist flowing
26 Properties of Substances Surface Tension How difficult it is to break the surface of a liquid
27 Properties of Substances Evaporation A change from liquid to gas
28 Properties of Substances Melting PointThe temperature at which a substance changes from solid to liquid or vice-versaBoiling PointThe temperature at which a substance changes from liquid to gas or vice-versa
29 How Do you Think IM Forces Affect the Following? ViscosityThe ability of a substance to resist flowingSurface TensionHow difficult it is to break the surface of a liquidEvaporationA change from liquid to gasSate of MatterBoiling PointMelting Point
30 How Do you Think IM Forces Affect the Following? Viscosity high viscosity = STRONG IM Forces Surface Tension high surface tension = STRONG IM Forces Evaporation fast evaporation rates = WEAK IM Forces Sate of Matter High BP = STRONG IM Forces High MP = SRONG IM Forces