Which statement best explains why saturated fatty acids tend to be solid at room temperature?

Which statement best explains why saturated fatty acids tend to be solid at room temperature?

• A. They contain double bonds
• B. They pack tightly
• C. They have long hydrocarbon tails
• D. They are soluble in water

Answer: (B)

The state of fats at room temperature is determined by how tightly their hydrocarbon chains can pack together. Saturated fatty acids have no double bonds, so their chains are straight and can align closely in a dense, orderly arrangement. This tight packing increases the van der Waals interactions between molecules, meaning more energy is needed to melt them, so they are solid at room temperature. Unsaturated fatty acids, with one or more double bonds, have kinks that prevent such tight packing, making them liquids. While longer tails can raise melting point due to stronger dispersion forces, the primary reason saturated fats are solid is their ability to pack tightly because the chains are straight. Solubility in water is not a determining factor here.

The state of fats at room temperature is determined by how tightly their hydrocarbon chains can pack together. Saturated fatty acids have no double bonds, so their chains are straight and can align closely in a dense, orderly arrangement. This tight packing increases the van der Waals interactions between molecules, meaning more energy is needed to melt them, so they are solid at room temperature. Unsaturated fatty acids, with one or more double bonds, have kinks that prevent such tight packing, making them liquids. While longer tails can raise melting point due to stronger dispersion forces, the primary reason saturated fats are solid is their ability to pack tightly because the chains are straight. Solubility in water is not a determining factor here.