CBSE Class 12-science Answered

Dear student,

Even though the total charge on a molecule is zero, the nature of chemical bonds is such that the positive and negative charges do not completely overlap in most molecules. Such molecules are said to be polar because they possess a permanent  dipole moment. A good example is the dipole moment of the   water molecule. Molecules with mirror symmetry like oxygen, nitrogen, carbon dioxide, and carbon tetrachloride have no permanent dipole moments. Even if there is no permanent dipole moment, it is possible to induce a dipole moment by the application of an external electric filed.The dipolar interaction between water molecules represents a large amount of internal energy and is a factor in water's large   specific heat. The dipole moment of water provides a "handle" for interaction with microwavew electric fields in a microwave oven. Microwaves can add energy to the water molecules, whereas molecules with no dipole moment would be unaffected.

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