Fatty acids are the building blocks of fats in our body. 

Physical Properties 

• Fatty acids are soluble in organic solvents such as benzene, chloroform, and alcohol 
• Solubility is inversely proportional to carbon chain length, increasing as the carbon chain length decreases and decreasing as the carbon chain length increases
• Fatty acids are insoluble in water
• They are bad conductors of heat
• Long chain saturated fatty acids are solid at room temperature, while long chain unsaturated fatty acids are liquid at room temperature
• Unsaturated fatty acids show cis-trans isomerism due to presence of double bonds
• Boiling points of saturated fatty acids keeps rising with increasing chain length 

Chemical Properties

• Hydrolysis:  Hydrolysis by alkalis such as NaOH or KOH generates sodium or potassium salts of fatty acids
• Hydrogenation: Oils containing unsaturated fatty acids undergo hydrogenation when exposed to high temperature, pressure, and finely divided nickel. This process converts oils into solid fats. 
• Hydrogenolysis: Hydrogenolysis involves the splitting of fat by hydrogen. In this process, hydrogen is passed through fat under pressure in the presence of copper-chromium catalyst. 
• Halogenation: Halogenation involves treating unsaturated fatty acids with halogens such as chlorine and iodine. During this process, the unsaturated fatty acid takes up iodine or other halogens at their double bond site, which is an indication of its unsaturated state. 
• Rancidity: When fats that are stored for long periods of time come in contact with light, moisture, heat, and air, they undergo chemical changes that result in them developing an unpleasant rancid odor. 
• Emulsification: Emulsifying agents such as bile juice secreted by the liver, water, proteins, soaps, and gums, break down large-sized fat molecules into smaller molecules in a process known as emulsification.