Intermolecular Forces

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by gwendolynmg88
Last updated 7 years ago

Discipline:
Science
Subject:
Chemistry
Grade:
10

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Intermolecular Forces

Polarity is based on the difference in electronegativity between atoms in a compound and the structure’s asymmetry. Electronegativity in an atom increases as the number of electron shells decrease and increases as the number of electrons increase in a shell. When determining if a molecule is polar or nonpolar you must draw the lewis dot structure of the molecule. Then you have to check if the molecule has any lone pairs. If it does, then the molecule is polar, but if there are no lone pairs present, check to see if the molecule is symmetric or asymmetric. If the molecule is symmetric it is non polar; if it is asymmetric it is polar.The degree of polarity is the electronegativity of elements in a bond. Strongest to weakest bonds: covalent network, ionic bonds, metallic bonds, and covalent compounds which include hydrogen bonds, dipole-dipole moments, and London dispersion forces. Delta positive and delta negative represent the dipoles in a molecule. A dipole moment is like a magnet where like charges repel and opposite charges attract. Polarity is the reason for certain physical properties, such as, surface tension, viscosity, and melting and boiling points. Usually when the polarity of a compound is high, its boiling point is higher as well.Nonpolar examples: CO2 or CH4Polar examples: H2O or SO3Covalent bonds are rather intramolecular forces rather than intermolecular forces. Network covalent means there are no individual molecules and they form a macromolecule (any kind of crystal). These structures have high melting points and boiling points and are insoluble in water. The forces holding ions together in ionic solids are electrostatic forces. Opposite charges attract each other. These are the strongest intermolecular forces. Ionic forces hold many ions in a crystal lattice structure. Valence electrons in metals are wild. They are not restricted to certain atoms or bonds. They run freely in the entire solid which provides good conductivity for heat and electric energy. Covalent compounds include hydrogen bonding, dipole-dipole interactions, and London dispersion forces; increasing in that order.

INTERMOLECULAR FORCES

1 ' 2Lewis Dot Structures and Molecular Geometry

3 ' 4Polarity and Intermolecular Forces

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Halayna Higgins 1-2Gwen Garr 3-4Hannah VanDivier 5-6Delanie Warren 7

5 ' 6Liquids and Solids

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7Phase Diagrams

Triple point is a phase where the lines of equilibrium meet. It allows gas, liquid, and solid at the pressure and temperature. Acritical point is the end point of a phase wquilbrium curve. The critical point is where a liquid and a vapor exists. A supercritical is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. It can effuse through solids like a gas, and can dissolve materials like liquid.

Lewis Dot Structures are representations of molecules depicting the bonds between atoms of a molecule by using dots to represent the electrons around the atom and lines to represent the covalent bonds between atoms. There are 3 steps to writing the Lewis Dot Structure of a molecule.3 StepsStep One: Count the total numer of valence electronsex: S6O3 6x6+6x3=54 valence electronsStep Two: draw the lewis dot structure . . . .:O--S--O: ' ' || ' ' :O:Step Three: Check otects, move double bonds where applicable. ex:SeO3 . . . .:O--S--O: ' ' || ' ' :O: all have 8 electrons around their symbolMolecular Geometry:Lone pairs- a pair of electrons that are not shared with another atom.Bent and trigonal pyramidal both have lone pairs making them polar.Bond pairs- the number of atoms bonded to the central atom.

Liquids:Properties: disorder, particles or clusters of particles are free to move relative to each other; particles close together. Image result for liquid structureIndefinite shape (takes shape of container)Fixed volume (can't be compressed, can't expand much)1000 x denser than gas molecules in a liquid are constantly in motionFlow readily, liquids that mix will eventually form a homogeneous mixture. Surface Tension- Net inward force experienced by molecules on the surface of a liquid.Surfactants reduce surface tension. Surfactants are a hybrid of non-polar and polar molecules, which means they can dissolve both types of liquids.Cohesion- molecules that are attracted to itself/themselvesAdhesion- molecules that are attracted to its surroundings.Capillary Action- the ability of a liquid to rise up a narrow tube/space.Viscosity- (related to ease in which molecules move) Resistance of a liquid to flow. Increases with stronger intermolecular forces, and decreases at higher temperatures.Volatility- (on unit 6 packet) Rate at which a chemical will evaporate. Increases with temperature and decreases with pressure.Extra Tidbit: The stronger the intermolecular force the harder it is to evaporate. Solids:Properties of solids- Definite shape (particles fixed in a place and vibrate, don't move)Fixed volumeEither Crystalline or AmorphousCrystalline particles are in regular, repeating patterns.Amorphous particles are unorganized/disorder.Greater density than a gasDon't mix by diffusion, particles in solids don't move or mix.Ionic solids have Crystalline solids.


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