Saturated fatty acids are always liquid at room temperature, while unsaturated fatty acids are always solid.
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Saturated fatty acids contain at least one double bond, while unsaturated fatty acids have only single bonds between carbon atoms.
Verified step by step guidance
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Step 1: Understand the structure of fatty acids. Fatty acids are long hydrocarbon chains with a carboxylic acid group (-COOH) at one end. The presence or absence of double bonds in the hydrocarbon chain determines whether a fatty acid is saturated or unsaturated.
Step 2: Define saturated fatty acids. Saturated fatty acids have no double bonds between the carbon atoms in their hydrocarbon chain. This means all carbon atoms are fully 'saturated' with hydrogen atoms, resulting in a straight chain structure.
Step 3: Define unsaturated fatty acids. Unsaturated fatty acids contain one or more double bonds between carbon atoms in their hydrocarbon chain. These double bonds introduce kinks or bends in the chain, which affect their physical properties.
Step 4: Compare the physical properties of saturated and unsaturated fatty acids. Saturated fatty acids are typically solid at room temperature due to their straight chains, which allow them to pack closely together. Unsaturated fatty acids, with their kinks, are usually liquid at room temperature because they cannot pack as tightly.
Step 5: Evaluate the given options. The correct description is that saturated fatty acids have no double bonds between carbon atoms, while unsaturated fatty acids contain one or more double bonds. This aligns with the structural definitions provided in Steps 2 and 3.