Final answer:
When an electric field is applied to polar molecules, they align themselves with the field direction, with positive ends towards the negative plate, and vice versa. This is due to the dipole moment of the molecules. Nonpolar molecules can also become temporarily polarized and align similarly within an electric field.
Step-by-step explanation:
When an electric field is applied to polar molecules, such as hydrofluoric acid (HF), their natural random orientation in a liquid state becomes aligned with the field. This is due to the molecule's dipole moment, a result of an uneven distribution of positive and negative charges within the molecule.
The positive ends, or 'heads', of the dipoles are attracted toward the negative plate, while the negative ends, or 'tails', are attracted toward the positive plate. This alignment effect is also seen in nonpolar molecules, but it occurs through induced dipoles, where the external field causes a temporary separation of charges within the molecule.
The phenomenon demonstrates the molecular response to an electric field and is significant in understanding the behavior of substances in electric fields, which is essential in fields like materials science and electrochemistry. The molecule's orientation in the electric field can affect how the field interacts with the substance containing the molecules, commonly weakening the effective field within materials known as dielectrics.