What affects the melting and boiling points of vegetable oils? 1. The size of the oil molecule Small oil molecules have lower melting and boiling points. Larger oil molecules have higher boiling and melting points. Why ? The forces acting between the molecules are larger.

2. The amount of saturation in the oil molecules HHHHHH HHHH C CCCC C HH HHHH H C CC C C C H * Saturated oils stack on top of each other very efficiently. *Unsaturated oils do not fit together so well * the intermolecular forces are weaker. * they have lower melting and boiling points Why do vegetable oils tend to be liquid at room temperature? Saturated * strong forces hold molecules together * SOLID at room temperature Unsaturated

How can we increase the melting / boiling points of unsaturated oils ?3. Hardening - react the oil with hydrogen so the oil becomes solid at room temp. (higher melting point) HHHH H C CC C C C H HH HH HH Nickel Catalyst 60°C This chemical reaction is called h hh hydrogenation. The hydrogen molecules react with the double bonds. Oils treated in this way are called h hh hydrogenated oils. HHHHHH HHHH C CCCC C HH HHHH H C CC C C C H

Summary Oil Oil has the higher boiling point than water. method of cooking potato fry in oil boil in water colour cooking time fat content texture brown pale quicker longer high low crispy soft Complete the following sentences using words from the list: energy hardening hydrogen melting tastes force Food cooked in oil different to boiled food. It also contains more. The boiling and points of oils can be raised by adding to their molecules. This process increases the amount of between the oil molecules. We call this the oil. Conditions needed in the hydrogenation reaction: Nickel catalyst 60°C tastes e h