Carbon Compounds

This chapter asks why oil palm is special compared with other sources of cooking oil such as soya bean, and covers carbon compounds, hydrocarbons, alcohol, fats and palm oil p. 140. The composition of greenhouse gases including carbon dioxide in the atmosphere continues to rise p. 141.

5.1 Introduction to Carbon Compounds

Carbon compounds are compounds which contain the element carbon, C, and are divided into organic carbon compounds and inorganic carbon compounds p. 142. Organic carbon compounds originate from living things, such as petroleum, silk and charcoal, while inorganic carbon compounds originate from non-living things, such as limestone and carbon dioxide p. 142. The carbon cycle shows how carbon elements are recycled through respiration, combustion, decomposition and photosynthesis p. 142. In the carbon cycle, dead organisms form fossil fuels such as petroleum, natural gas and coal p. 142.

Carbon dioxide is released into the atmosphere through the respiration of all living things, the burning of fossil fuels, and decomposition by bacteria and fungi p. 143. Volcanic eruptions and forest fires also release carbon dioxide into the atmosphere p. 143. Green plants absorb carbon dioxide for photosynthesis, which provides food to animals, increases the oxygen content in the air and removes excess carbon dioxide from the air p. 143.

5.2 Hydrocarbons

Hydrocarbon compounds are organic carbon compounds made up of only carbon and hydrogen elements p. 145. Petroleum and natural gas, and coal, form from natural sources p. 145. Petroleum is a mixture of hydrocarbons that is separated through fractional distillation because the petroleum fractions have different boiling points p. 146. In Activity 5.2, crude oil is heated in a boiling tube and the petroleum vapour released is highly flammable p. 146. The four fractions are collected from room temperature to 80 °C, 80 °C to 150 °C, 150 °C to 230 °C and 230 °C to 250 °C, then compared for colour, viscosity and flammability p. 147.

A homologous series is a specific group of organic compounds which have similar chemical properties, such as the alkane and the alkene p. 148. Alkanes are saturated hydrocarbons in which each carbon atom forms single covalent bonds, with the general formula CₙH₂ₙ₊₂ where n = 1, 2, 3, … p. 148. Alkenes are unsaturated hydrocarbons with at least one double covalent bond between two carbon atoms, with the general formula CₙH₂ₙ where n = 2, 3, … p. 148. The first six alkanes are methane, ethane, propane, butane, pentane and hexane, and the first five alkenes are ethene, propene, butene, pentene and hexene p. 149.

Fossil fuels such as petroleum, coal and natural gas are non-renewable energy sources which are fast depleting p. 149. Alternative energy sources will not deplete easily, such as nuclear energy or renewable energy sources like solar, wind, hydroelectric, biomass, geothermal, tidal and wave energy p. 149. Rubbish disposal sites release carbon dioxide and methane gases from organic waste decay, and some countries use methane gas to generate electrical energy p. 150. Methane gas is highly flammable p. 150.

5.3 Alcohol

Alcohol is an organic carbon compound which contains carbon, hydrogen and oxygen elements p. 150. Alcohol is prepared through fermentation by the action of yeast on food containing glucose or starch such as sugar, grapes, apples, sugarcane, rice, wheat, potato and barley p. 150. In the fermentation process, the zymase in yeast converts glucose into ethanol and carbon dioxide p. 151. In Activity 5.5, 100 g of sugar, bread or fruit is mixed with 50 cm³ of distilled water and 10 g of yeast, and the gas is passed through limewater p. 151. After one week the mixture is filtered and distilled, and the distillate is collected at a temperature of 78 °C p. 152.

Alcohol is colourless, liquid at room temperature and has a distinctive smell p. 153. Its boiling point increases and its solubility in water decreases when its number of carbon atoms increases p. 153. In Activity 5.6, the gas released from burning ethanol is tested with limewater and the droplets formed are tested with dry cobalt chloride paper p. 153. Ethanol and ethanoic acid are heated with five drops of concentrated sulphuric acid in a fume chamber, and the product is poured into water p. 154.

Alcohol is a good fuel because it is highly flammable, burns with a blue flame and produces a complete and clean combustion without soot p. 155. Alcohol is used as an antiseptic and disinfectant, and as a solvent for medicine and for cosmetics such as perfume, lotion and lipstick p. 155. In industry, alcohol is a solvent and a reactant in the formation of ester, and ethanediol is used as an antifreeze p. 155.

Excessive alcohol consumption causes addiction, dangerous driving and altercations p. 156. Expectant mothers who consume excessive alcohol can cause foetal alcohol syndrome, in which babies have a small head and brain, abnormal face and stunted growth p. 156. Excessive alcohol consumption damages brain cells, causes blurred vision, an increased rate of heartbeat, high blood pressure, stomach ulcers and liver cirrhosis p. 156.

5.4 Fats

Solid fats at room temperature usually originate from animals such as chicken, cow, goat and fish, while oil normally originates from plants, such as palm oil, coconut oil and soya bean oil p. 158. Saturated fats and unsaturated fats are both organic compounds containing carbon, hydrogen and oxygen that do not dissolve in water p. 158. Saturated fats come from animals, are solid at room temperature and have a high melting point, while unsaturated fats come from plants, are liquid and have a low melting point p. 158.

Eating food containing excess fats, especially saturated fats, will increase the level of cholesterol in the blood p. 158. Cholesterol is needed for building cell membranes, synthesising bile and sex hormones, and producing vitamin D in skin exposed to sunlight p. 158. Excessive cholesterol can form gallstones which block the bile duct and cause jaundice p. 159. Cholesterol deposited on the inner artery walls narrows the lumen in a condition known as atherosclerosis p. 159. Atherosclerosis can cause hypertension, stroke and fatal heart attack, so the intake of saturated fats should be reduced p. 159.

5.5 Palm Oil

The oil palm fruit is made up of the pulp (mesocarp), which contains the most palm oil, the kernel, which contains the best quality palm kernel oil, and the shell (endocarp), which does not contain oil p. 160. In Activity 5.9, the oil palm fruits are boiled for 20 minutes before the pulp is separated from the shell and squeezed in a press p. 161.

In the industrial extraction process, the bunch of oil palm fruits is sterilised with steam at a high pressure and temperature, which kills bacteria and fungi and softens the pulp p. 162. Threshing detaches the fruits from their bunches, and digestion separates the pulp from the shell using rotating beater arms p. 162. The pulp is squeezed with a hydraulic or spindle press, filtered, and purified with steam and activated carbon to give pure palm oil p. 162. The kernel is dried and pressed to extract palm kernel oil, then filtered p. 162.

Palm oil is made up of glycerol and various types of fatty acids p. 163. It contains saturated fatty acids such as palmitic acid and stearic acid, and unsaturated fatty acids such as oleic acid and linoleic acid p. 163. In Table 5.3, palm oil has a ratio of unsaturated fats to saturated fats of 1.0, with 45% palmitic acid and 40% oleic acid p. 164.

Oxidation of palm oil produces free radicals and compounds which are harmful to human health p. 165. Hydrolysis of palm oil with water produces glycerol and fatty acids, and esterification with alcohol produces methyl ester, that is palm oil biodiesel p. 165. Emulsification breaks palm oil into smaller droplets, which increases the total surface area of the palm oil p. 165. Palm oil is a balanced oil with the same amount of saturated fats and unsaturated fats and is a rich source of vitamin E and vitamin A p. 165. Palm oil contains antioxidants such as carotene and vitamin E which slow down or stop the oxidation process p. 166. Palm oil is used in cooking oil, vegetable oil, margarine and chocolate p. 166.

Soap is a fatty acid salt produced through the reaction between palm oil and concentrated alkali, such as concentrated sodium hydroxide or concentrated potassium hydroxide p. 167. In Experiment 5.1, 10 cm³ of palm oil is boiled with 50 cm³ of 5 mol dm⁻³ concentrated sodium hydroxide solution for 5 minutes p. 167. Distilled water and sodium chloride are then added, the mixture is boiled again and filtered, and the residue is tested with red and blue litmus papers p. 168.

A soap molecule has a hydrophilic ‘head’, an ionic group that dissolves in water, and a hydrophobic ‘tail’, a hydrocarbon chain that dissolves in oil or grease p. 168. When soap dissolves in water, the surface tension of the water is reduced, and the hydrophobic part attaches to the greasy dirt while the hydrophilic part dissolves in water p. 169. Scrubbing dislodges the greasy dirt into droplets surrounded by soap molecules, which are removed during rinsing p. 169.

Sustainable management in the palm oil industry includes replanting to optimise land use and turning palm oil mill effluent (POME) into organic fertilisers and biogas p. 169. The quality of air improves when oil palm trees absorb carbon dioxide and release oxygen during photosynthesis p. 170. The zero waste concept turns fronds into fertilisers, empty fruit bunches into compost and pulp fibre into carpets and textile p. 170. The oil palm industry has been linked to deforestation when forests are burnt to provide land for planting oil palm trees p. 171.