Why is butter solid and mustard oil liquid at room temperature?

The difference in the physical state of butter and mustard oil at room temperature can be attributed to several factors:

1. Fatty Acid Composition:

- Butter: Butter is composed of various fatty acids, including saturated and unsaturated fats. Saturated fats have a higher melting point compared to unsaturated fats. The high content of saturated fats in butter contributes to its solid state at room temperature.

- Mustard Oil: Mustard oil, on the other hand, is predominantly composed of unsaturated fatty acids, such as oleic acid and linoleic acid. Unsaturated fats have a lower melting point compared to saturated fats. This lower melting point causes mustard oil to remain liquid at room temperature.

2. Molecular Structure:

- Butter: The saturated fatty acids in butter have a straight molecular structure. This allows them to pack closely together, resulting in a higher melting point and a solid consistency at room temperature.

- Mustard Oil: The unsaturated fatty acids in mustard oil have a bent or kinked molecular structure. This structure prevents the molecules from packing as tightly as saturated fats, resulting in a lower melting point and a liquid state at room temperature.

3. Triglyceride Composition:

- Butter: Butterfat is made up of triglycerides, which are molecules that consist of three fatty acids attached to a glycerol backbone. The majority of triglycerides in butter contain a combination of saturated and unsaturated fatty acids. This mixed composition contributes to butter's semi-solid texture at room temperature.

- Mustard Oil: Mustard oil is also composed of triglycerides. However, these triglycerides primarily contain unsaturated fatty acids, particularly oleic acid. The high content of unsaturated fatty acids results in a lower melting point and a liquid state at room temperature.

In summary, the higher content of saturated fats, the straight molecular structure of saturated fats, and the predominant presence of unsaturated fatty acids in mustard oil explain the difference in their physical states at room temperature.