SS3 First Term Chemistry Lesson Note – Fats and Oils

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WEEK 3

TOPIC: FATS AND OILS

CONTENTS:

1. Sources
2. Physical and chemical properties i.e.
3. Reactions of fats and oils: hydrogenation and saponification
4. Uses

PERIOD 1: SOURCES

Fats and oils occur naturally in living things. There are two main sources.

1. Tissues of Animals. Marine (water) animals, like fish, provide fish oil and cod-liver oil, while terrestrial (land) animals provide butter, land and fallow.
2. Fruits and seeds of plants: they contain edible fat and oil such as cocoa butter, fat, palm oil, coconut oil, cotton seed oil, olive oil, corn oil, ground nut oil, sunflower seed oil, olive oil, corn oil and soya bean oil. They are called vegetable oils.

Physical and chemical properties

1. Physical properties

(i). Pure fats and oils are coloured or white and almost odourless.

(ii). Fats and oils do not have sharp boiling or melting points because they are complex mixtures of two or more different triglycerides (esters).

(iii). They are insoluble in water but soluble in organic solvents e.g. alcohols

(iv). When heated to temperatures above 300⁰C, fats and oils decompose to give irritating fumes

EVALUATION

• Name the two sources of fats and oils

Write four examples from each source

PERIOD 2 & 3: CHEMICAL PROPERTIES OF FATS AND OIL (REACTIONS OF FATS AND OILS – SAPONIFICATION AND HYDROGENATION)

HYDROGENATION OF OILS

Natural oils are largely triglycerides i.e., esters of unsaturated fatty acids. They exist as liquids, which are not edible. In order to make them edible, the unsaturated oils are usually hydrogenated so as to make them hard and obtain saturated edible fats.

Margarine is obtained from a refine mixture of animal fats and vegetable oils which have been treated with activated charcoal in order to remove the colour and odour and carefully neutralize the free acid.

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