Intermolecular and Intramolecular Forces

​INTER-molecular Forces & Physical Properties

Strength

Intramolecular bonds > intermolecular forces

Intramolecular bonds are stronger because it would take a lot more energy to overcome covalent bonds and break apart the molecule than to overcome intermolecular forces in between the atoms (to make it become a liquid or gas).

Multiple Choice

Forces that holds atoms together within the molecule

• intermolecular forces

• intramolecular forces

Multiple Choice

Intermolecular Forces are the forces that exist

• Between two or more molecules

• Within a single molecule

• Only in molecules containing carbon

• In all molecules

The polarity of molecules plays a crucial role in determining the strength and type of intermolecular forces. Polar molecules tend to exhibit dipole-dipole interactions and hydrogen bonding, while non-polar molecules can still experience London dispersion forces due to temporary fluctuations in electron distribution. The strength of these forces depends on the degree of polarity in the molecules involved.

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Multiple Choice

Which of the following factors plays an important role in the identification of specific intermolecular forces in a molecule?

• bond type
• density
• solubility
• molecular polarity

Multiple Choice

The intermolecular force present in all matter is

• Hydrogen Bonding

• Ionic Bonding

• Dipole-Dipole

• London or Dispersion

Multiple Choice

Examples of an intermolecular force include

• london disperson

• hydrogen bonding

• dipole dipole

• all of the above

Multiple Choice

The weakest IMF is

• Dipole-Dipole

• Dispersion

• Hydrogen Bonding

Multiple Choice

The strongest IMF is

• London/Dispersion

• Dipole-Dipole

• Hydrogen Bonding

With increasing attraction between molecules in a substance, the phase at room temperature goes from gas (least IMF) to solid (most IMF). The increased attractions between molecules decreases the amount of space between the molecules and decreases the ability of neighboring atoms to move freely without additional input energy.

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​Phase at Room Temperature

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Like dissolves like.” The stronger the intermolecular forces between solute molecule and solvent molecule, the greater the solubility of the solute in the solvent. Which why solubility is the best way to determine the strength of intermolecular forces among bond types

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​Solubility

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Resistance for a substance to flow

• With increasing attraction between molecules in a substance, viscosity increases.

• Molecule with higher number of IMF are more viscous (stick together more)

  • Think syrup compared to water and how easily they pour

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​Viscosity

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With increasing attraction between molecules in a substance, the temperature at which a substance boils increases.

• The stronger the intermolecular forces between the molecules of a liquid, the greater the energy required to separate the molecules and turn them into gas

  • Which means a higher boiling point

• Higher IMFs = Higher Melting and Boiling Point

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​Boiling Point/
Melting Point

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Multiple Choice

The weaker the intermolecular forces of a substance the _____________ the boiling point

• higher

• lower

Multiple Choice

For hydrogen bonding to occur, a molecule must have a hydrogen bonded to

• carbon

• another hydrogen

• Fluorine, Chlorine or Oxygen

• Fluorine, Nitrogen or Oxygen

Multiple Choice

In general, substances with stronger intermolecular forces have ________ boiling points than those with weaker forces

• Higher

• Lower

• The same

Multiple Choice

Which substance has the weakest intermolecular forces?

• Substance A, boiling point of 75 °C

• Substance B, boiling point of 105 °C

• Substance C, boiling point of 25 °C

• Substance d, boiling point of 45 °C

Multiple Choice

Which of the following is NOT a type of intramolecular force?

• Covalent bonding

• Hydrogen bonding

• Ionic bonding

• Metallic bonding

Multiple Choice

Rank these in order of strength (strongest to weakest):

London forces
hydrogen bond
dipole-dipole attraction

• dipole-dipole>hydrogen bond>London

• London>dipole-diple>hydrogen bond

• hydrogen bond>dipole-dipole>London

• hydrogen bond>London>dipole-dipole