Which fatty acid is solid at room temperature?

Which fatty acid is solid at room temperature?

• A. unsaturated
• B. saturated
• C. polyunsaturated
• D. trans-fatty acid

Answer: (B)

Saturated fatty acids are solid at room temperature because they have no double bonds, so their hydrocarbon chains are straight and can pack tightly together. This tight packing leads to strong intermolecular forces and a higher melting point, which keeps the fat solid at room temperature. In contrast, unsaturated fatty acids have one or more cis double bonds that introduce kinks in the chain, preventing tight packing and lowering the melting point, so these fats are usually liquids (oils) at room temperature. Polyunsaturated fats have even more cis double bonds, causing more bends and an even lower melting point, staying liquid. Trans-fatty acids have double bonds in the opposite (trans) orientation, which makes the chain more linear and can raise the melting point, but the typical distinction taught is that saturated fats are the ones that are solid at room temperature.

Saturated fatty acids are solid at room temperature because they have no double bonds, so their hydrocarbon chains are straight and can pack tightly together. This tight packing leads to strong intermolecular forces and a higher melting point, which keeps the fat solid at room temperature.

In contrast, unsaturated fatty acids have one or more cis double bonds that introduce kinks in the chain, preventing tight packing and lowering the melting point, so these fats are usually liquids (oils) at room temperature. Polyunsaturated fats have even more cis double bonds, causing more bends and an even lower melting point, staying liquid. Trans-fatty acids have double bonds in the opposite (trans) orientation, which makes the chain more linear and can raise the melting point, but the typical distinction taught is that saturated fats are the ones that are solid at room temperature.