State two major differences in their structures.

Describe how an oil can be converted into a fat.

Discuss two advantages and two disadvantages of converting oils into fats.

oils contain at least one C=C/carbon to carbon double bond;

oils have fewer carbon atoms in the hydrocarbon chains / OWTTE;

hydrogenation / react with hydrogen (gas);

heat/140−225 °C and metal catalyst/Ni/Zn/Cu/pressure;

Advantages: [2 max]

increases melting points / changes oil to a semi-solid/solid;

decreases rate of oxidation;

increases hardness;

controls feel/plasticity/stiffness;

Disadvantages: [2 max]

the more saturated the less good for the heart / OWTTE;

trans-fatty acids can be formed (through partial hydrogenation);

trans-fatty acids are difficult to metabolize / increase LDL levels / low quality energy source / accumulate in fatty tissue / are difficult to digest/excrete (from the body);

Most candidates compared structural features of fats and oils, but many failed to score as they missed the required specificity of carbon to carbon double bond in (a). A significant number of candidates compared melting points which was not part of the question and very few were able to state the difference in the length of hydrocarbon chains.

Many candidates gave detailed descriptions of the process to score both marks in part (b), but some failed to score the second mark by omitting the need of a catalyst/pressure and/or heat.

Many candidates were able to correctly suggest two advantages but failed to correctly state two disadvantages in part (c). Very often marks were lost as result of poor use of subject specific terms.