The Four Intermolecular Forces and How They Affect Boiling Points — Master Organic Chemistry
Dipole-dipole interactions are the strongest intermolecular force of attraction. This explains the exceptionally high boiling points and melting points of. In this lesson we will review what intermolecular forces are and how they will affect physical properties such as boiling point, freezing point. Answer to What is the relationship between the intermolecular forces in a solid and its melting temperature?.
Liquid water is essential for life as we know it, but based on its molecular mass, water should be a gas under standard conditions.
- Intramolecular and intermolecular forces
- The Four Intermolecular Forces and How They Affect Boiling Points
Why is water a liquid rather than a gas under standard conditions? Describe the effect of polarity, molecular mass, and hydrogen bonding on the melting point and boiling point of a substance.
Why are intermolecular interactions more important for liquids and solids than for gases?
How is melting point related to the intermolecular forces of attraction?
Under what conditions must these interactions be considered for gases? Using acetic acid as an example, illustrate both attractive and repulsive intermolecular interactions.
How does the boiling point of a substance depend on the magnitude of the repulsive intermolecular interactions? In group 17, elemental fluorine and chlorine are gases, whereas bromine is a liquid and iodine is a solid.
The boiling points of the anhydrous hydrogen halides are as follows: Think about an atom like argon. The fact that it forms a liquid it means that something is holding it together. Think about the electrons in the valence shell.
Physical Properties and Intermolecular Forces ( Read ) | Chemistry | CK Foundation
But at any given instant, there might be a mismatch between how many electrons are on one side and how many are on the other, which can lead to an instantaneous difference in charge. On average, every player is covered one-on-one, for an even distribution of players.
The polarizability is the term we use to describe how readily atoms can form these instantaneous dipoles. Polarizability increases with atomic size. For hydrocarbons and other non-polar molecules which lack strong dipoles, these dispersion forces are really the only attractive forces between molecules. Since the dipoles are weak and transient, they depend on contact between molecules — which means that the forces increase with surface area.
A small molecule like methane has very weak intermolecular forces, and has a low boiling point.
Now if I ask you to pull this assembly from both ends, what do you think will happen? The Velcro junctions will fall apart while the sewed junctions will stay as is. The attachment created by Velcro is much weaker than the attachment created by the thread that we used to sew the pairs of towels together.
A slight force applied to either end of the towels can easily bring apart the Velcro junctions without tearing apart the sewed junctions. Exactly the same situation exists in molecules. Just imagine the towels to be real atoms, such as hydrogen and chlorine.
These two atoms are bound to each other through a polar covalent bond—analogous to the thread. Each hydrogen chloride molecule in turn is bonded to the neighboring hydrogen chloride molecule through a dipole-dipole attraction—analogous to Velcro. The polar covalent bond is much stronger in strength than the dipole-dipole interaction.
The former is termed an intramolecular attraction while the latter is termed an intermolecular attraction.