In both water H2O and ammonia NH3 , the primary type of intermolecular force present is hydrogen bonding. Hydrogen bonding is a strong type of dipole-dipole interaction that occurs when a hydrogen atom is covalently bonded to a highly electronegative atom such as nitrogen, oxygen, or fluorine and is attracted to another electronegative atom in a neighboring molecule.In water, the oxygen atom is more electronegative than the hydrogen atoms, resulting in a polar covalent bond. The oxygen atom has a partial negative charge, while the hydrogen atoms have partial positive charges. This leads to the formation of hydrogen bonds between the oxygen atom of one water molecule and the hydrogen atom of another water molecule.Similarly, in ammonia, the nitrogen atom is more electronegative than the hydrogen atoms, creating a polar covalent bond. The nitrogen atom has a partial negative charge, while the hydrogen atoms have partial positive charges. This results in hydrogen bonding between the nitrogen atom of one ammonia molecule and the hydrogen atom of another ammonia molecule.These hydrogen bonds contribute to the physical properties of water and ammonia in several ways:1. Boiling and melting points: Hydrogen bonding leads to higher boiling and melting points for both water and ammonia compared to other molecules of similar size and molecular weight. This is because the hydrogen bonds need to be broken for the substances to change phase, which requires more energy.2. Surface tension: The hydrogen bonding in water and ammonia results in strong cohesive forces between the molecules, leading to high surface tension. This is why water forms droplets and can support small objects like insects on its surface.3. Viscosity: The hydrogen bonding in water and ammonia also contributes to their viscosity, making them more resistant to flow compared to other liquids with weaker intermolecular forces.4. Solvent properties: Water and ammonia are both excellent solvents for many ionic and polar compounds due to their polarity and hydrogen bonding capabilities. They can dissolve salts, sugars, and other polar molecules by surrounding and stabilizing the ions or molecules with their hydrogen bonds.5. Density: In the case of water, the hydrogen bonding leads to an unusual property where the solid form ice is less dense than the liquid form. This occurs because the hydrogen bonds in ice form a hexagonal lattice structure, which has open spaces and results in a lower density compared to the more random arrangement of molecules in liquid water. This is why ice floats on water.In summary, the hydrogen bonding present in water and ammonia is responsible for many of their unique physical properties, such as high boiling and melting points, surface tension, viscosity, solvent properties, and in the case of water, the lower density of ice compared to liquid water.