Forces between molecules

In summary, at low temperatures, the lower kinetic energy of particles leads to an attraction between molecules due to opposite charges, resulting in a negative B value. However, at high temperatures, the increased kinetic energy causes repulsive forces to arise between particles, resulting in a positive B value. This is due to the convention that attractive forces have a negative sign and repulsive forces have a positive sign.
  • #1
pentazoid
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Homework Statement



Think about forces between molecules, and explain why we might expect B(cm^3/mol) to be negative at low temperatures but positive at high temperatures.


Homework Equations





The Attempt at a Solution



Well at low temperatures the motion of particles are not as high as they would be at high temperatures, so there is less kinetic energy so wouldn't they attract each other and opposite charges attractive but the product of two different charges are negative. As the temperature increases, the kinetic energy increases and attrative intermolecular forces begin to break apart and therefore a repulsive forces arises between the particles. Therefore the charges of the particle either must be both positive or both negative , therefore the product of the charges of the two particles are positive.
 
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  • #2
I think what you've said so far is fairly correct. This also ties in with the fact that attractive forces have a negative sign associated with them, and repulsive forces are positive by convention.
 

1. What are intermolecular forces?

Intermolecular forces are the attractive or repulsive forces between molecules. They are responsible for holding molecules together in a substance and determining its physical properties.

2. What are the different types of intermolecular forces?

The three main types of intermolecular forces are dispersion forces, dipole-dipole interactions, and hydrogen bonding. Dispersion forces are the weakest and occur between all molecules. Dipole-dipole interactions occur between polar molecules, and hydrogen bonding is a special type of dipole-dipole interaction that occurs when hydrogen is bonded to a highly electronegative atom.

3. How do intermolecular forces affect boiling and melting points?

The strength of intermolecular forces increases with increasing molecular size and polarity. As a result, substances with stronger intermolecular forces will have higher boiling and melting points, as it takes more energy to overcome these forces and change the state of the substance.

4. How do intermolecular forces impact solubility?

Intermolecular forces also play a role in solubility. Like dissolves like, meaning substances with similar intermolecular forces will be more likely to dissolve in each other. For example, polar substances will dissolve in polar solvents, while nonpolar substances will dissolve in nonpolar solvents.

5. Can intermolecular forces be altered?

Yes, intermolecular forces can be altered by changing the temperature or pressure of a substance. Increasing the temperature will increase the kinetic energy of the molecules, making it easier to overcome intermolecular forces. Similarly, increasing the pressure can also affect the strength of intermolecular forces.

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