Van Der Waals forces are weak electrostatic interactions between atoms or molecules that are not covalently bonded. These forces arise from the temporary dipoles that occur when the electron density around an atom or molecule is not evenly distributed. They are named after Dutch scientist Johannes Diderik van der Waals, who first described them in the late 19th century.
There are three types of Van Der Waals forces: dispersion forces, dipole-dipole interactions, and hydrogen bonding. Dispersion forces, also known as London forces, are the weakest and occur between all molecules. Dipole-dipole interactions occur between polar molecules, while hydrogen bonding is a special type of dipole-dipole interaction that occurs between molecules containing hydrogen bonded to a highly electronegative atom such as oxygen, nitrogen, or fluorine.
Van Der Waals forces play a significant role in determining the physical properties of substances. They contribute to the boiling and melting points of substances, as well as their viscosity and surface tension. They also affect the solubility and intermolecular interactions between molecules.
No, Van Der Waals forces are much weaker than covalent bonds. Covalent bonds involve the sharing of electrons between atoms, whereas Van Der Waals forces are only temporary interactions between molecules. Covalent bonds are typically 10 to 100 times stronger than Van Der Waals forces.
Van Der Waals forces can be manipulated or controlled through changes in temperature, pressure, and molecular structure. Higher temperatures and pressures can weaken Van Der Waals forces, while lower temperatures and pressures can strengthen them. Additionally, altering the size and shape of molecules can also affect the strength of Van Der Waals forces.