Lecture 07 intermolecular forces

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Lecture 07 intermolecular forces

Intermolecular Forces Intramolecular forces bonding forces exist within molecules and influence the chemical properties. Intermolecular forces exist between molecules and influence the physical properties.

We can think of H2O in its three forms, ice, water and steam. In all three cases, the bond angles are the same, the dipole moment is the same, the molecular shape is the same and the hybridization of the oxygen is the same. However, the physical properties of H2O are very different in the three states.

As solid ice, H2O possesses a definite shape and volume. Liquid water possesses a definite volume, but will assume the shape of its container. It is slightly compressible. Steam will assume both the shape and volume of its container and is extremely compressible.

Intermolecular forces IMF are the forces which cause real gases to deviate from ideal gas behavior. They are also responsible for the formation of the condensed phases, solids and liquids.

The IMF govern the motion of molecules as well. In Lecture 07 intermolecular forces gaseous phase, molecules are in random and constant motion.

Lecture 07 intermolecular forces

Each gas molecule moves independently of the others. In liquids, the molecules slide past each other freely. In solids, the molecules vibrate about fixed positions. Heating Curves The transitions between the phases, phase changes, can be viewed in terms of a Heating Curve, like the one shown below, for water.

It is a plot of time versus temperature. The time axis represents the addition of heat as a function of time. The longer the time span, the more heat has been added to the system. In this Heating Curve, we are starting with ice at oC. As we add heat, we raise the temperature of the ice.

In the solid phase, the allowed motions are in vibrational movements within the molecules. In the case of water, the O-H bonds are stretching and bending. The bond lengths and angles are oscillating around the predicted values.

The amount of heat required to raise the temperature of the ice is determined by the heat capacity of ice, the heat required to change the temperature of 1 gram of ice by 1oC. The heat capacity of each phase of each substance is unique, and depends on the chemical nature of the substance.

When the temperature reaches 0oC, the melting point of ice, further addition of heat does not change the temperature. At this phase transition temperature, the added energy goes to changing the Potential Energy of the system. It is coulombic in nature, arising from the attraction of charged species.

In the case of H2O, it is the attraction between the partial positive charges on the H and the partial negative charges on the O. As we discussed earlier in the semester, these are hydrogen bonds, holding the water molecules in the crystalline structure of ice.

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At the phase transition temperature, 0oC, all of the ice will be converted to liquid water. The increase in temperature is, again, an increase in the KE of the system. The movement of the water molecules will increase in the liquid phase. There is still some degree of hydrogen bonding between molecules, but they are no longer in fixed positions in a crystal lattice.

There is a second phase transition at oC.Lecture 24 Intermolecular forces. 2 where we’ve been and where the (almost) last 1B lectures take us • have studied intramolecular forces among molecular structure and intermolecular forces (problem 71 and 72) Zumdahl # Identify the .

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Intermolecular Forces. Intramolecular forces (bonding forces) exist within molecules and influence the chemical properties.

LECTURE INTRODUCTION TO INTERMOLECULAR FORCES As we ended the lectures on gases, we were introduced to an idea that serves as foundation for the material in this lecture: As we were introduced to ideal gases, we learned from kinetic . Lecture Intermolecular Forces and Alkanes. Last time we looked at the two extremes of bonding, ionic bonding, in which electron transfer leads to the formation of an anion and a cation which are held together by electrostatic attraction, and covalent bonding, an equal sharing of bonding electrons between atoms of equal electronegativity. Between these two extremes lie the most common bonds. last lecture: introduction to intra- and intermolecular forces (within individual molecules) (between individual molecules)→ no real physical difference -Definitions: Interaction (more general), force (push or pull), bond (the attraction between atoms in a molecule or.

Intermolecular forces exist between molecules and influence the physical properties. We can think of H 2 O in its three forms, ice, water and steam.

Lecture 07 intermolecular forces

In all three cases, the bond angles are the same, the dipole moment is the . Lecture 24 Intermolecular forces.

Organic Chemistry Causes[ edit ] Diagram of the forces on molecules of a liquid Due to the cohesive forces a molecule is pulled equally in every direction by neighboring liquid molecules, resulting in a net force of zero.
Build a bibliography or works cited page the easy way We looked at an assortment of alkanes in lecture.
Los Rios Community College District Intermolecular Forces Intramolecular forces bonding forces exist within molecules and influence the chemical properties. Intermolecular forces exist between molecules and influence the physical properties.
Chem 1A. Lec. General Chemistry. Dipole Forces, Dispersion Forces :: UC Irvine, UCI Open We looked at an assortment of alkanes in lecture.

2 where we’ve been and where the (almost) last 1B lectures take us • have studied intramolecular forces among molecular structure and intermolecular forces (problem 71 and 72) Zumdahl # Identify the .

Intermolecular Forces Intermolecular forces are forces of attraction or repulsion which act between neighboring particles (atoms, molecules or ions). They are weak compared to the intramolecular forces, the forces which keep a molecule together.

last lecture: introduction to intra- and intermolecular forces (within individual molecules) (between individual molecules)→ no real physical difference -Definitions: Interaction (more general), force (push or pull), bond (the attraction between atoms in a molecule or.

Surface tension can be defined in terms of force or energy. In terms of force: surface tension γ of a liquid is the force per unit length. In the illustration on the right, the rectangular frame, composed of three unmovable sides (black) that form a "U" shape, and a fourth movable side (blue) that can slide to .

Intermolecular Forces