Form 5 Science Chapter 4: Carbon compounds

Form 5 Science Chapter 4: Carbon compounds

Organic compounds Similarity Inorganic compounds

Both have carbons

Differences

Obtained from living things Sources Obtained from non-living things

Yes

Burning in air to produce carbon dioxide No

Big Molecular size Small

Soluble Solubility in organic solvents Insoluble

Carbohydrates, proteins, vitamins, silk, gasoline

Examples Carbon monoxide, calcium carbonate, carbon dioxide

• Carbon compounds are compounds that contain the element, carbon, combined chemically with one or more other elements.

• Carbon compounds can be divided into two types, namely organic compounds and inorganic compounds.

Form 5 Science: Chapter 4 (Prepared by Dr. You L.L.) 1

The formation of natural gas and petroleum

The formation of coal

• Hydrocarbons are compounds that contain the elements, carbon and hydrogen only. • Petroleum originates from the remains of plants and animals which died and were embedded in the sea millions of

year ago. • Natural gas is trapped in between impermeable rocks with petroleum in the ground. • Coal originated from plants in the marshes that were buried underground millions of years ago.

Hydrocarbons


Uses of alcohol • As an organic solvent to dissolve complex organic molecules

(perfumes, cosmetics, medicines, printing inks, paint and industrial detergent).

• Disinfectants—to kill harmful bacteria. • Fuel- this fuel does not produce many pollutants. • Alcoholic drinks (Shandy, Beer, Wine, Brandy, and Whisky).

The effects of alcohol on health • Affect the body coordination (slow down the transmission of impulses, poor balance). • Eyes difficult to focus, more saliva and more frequent urination. • Causes insane thoughts • Heart rate increased, blood pressure raised, heart rhythm disturbed. • Damage the liver, causing cirrhosis of the liver. • Causes gastritis, corrodes the lining of stomach • Pregnant women should avoid alcoholic drinks (Foetal alcohol syndrome).

• Alcohols are compounds containing three elements carbon, hydrogen and oxygen.

• Alcohols have the same functional group, the hydroxyl group, (-OH), at the end of the hydrocarbon chain.

Physical characteristics of alcohol • Liquid at room temperature • Colourless • Perfume smell • Vapourise easily • Soluble in water

Alcohols


Combustion of alcohol • Burns easily • Burns with light blue

flame without soot

Combustion of alcohol Alcohol is colourless, strong smell, volatile, soluble in water and combustible

Alcohol + oxygen ---------------> Carbon dioxide + water

Esterification When alcohol reacts with an organic acid, an ester and water are formed (esterification).

Concentrated sulphuric acid (catalyst) Alcohol + organic acid ---------------------------------------> Ester + water

Ester is a colourless liquid which does not dissolve in water, sweet-smelling and volatile. Thus they are widely used in food

flavouring, fragrances and cosmetics.


Fermentation of glucose

Glucose + Yeast Ethanol + Carbon dioxide + Heat

• Alcohol can be produced from raw food materials such as grains, rice, barley and sweet fruits such as grapes, sugarcane and pineapple.

• Sugar and starch in the food are converted into alcohol by the action of yeast through the process of fermentation.


Distillation of ethanol


Saturated fats Differences Unsaturated fats

Present of double bond

X Able to react with other atom √

Solid Condition at room temperature Liquid

Increase level of bad cholesterol [LDL]

Effects on blood cholesterol level Increase level of good cholesterol [HDL]

√ (arteriosclerosis)

Cause diseases to the heart and arteries

X

higher Melting point Lower

Animal fats: butter and ghee

Examples Vegetable oil: palm oil, coconut oil, peanut oil, soya oil, corn oil and olive oil

• Human body also needs fats for generating energy. Fats provide twice as much energy compared to carbohydrates.

• There are two types of fats, saturated fats and unsaturated fats.

Fats


• Saturated fats have high cholesterol content. • Excess cholesterol in the blood is deposited on the walls of

arteries and the lumens become narrow. • This condition causes: High blood pressure. Arteriosclerosis (thickening of the walls of the arteries). Heart attack Stroke

The effect of intake of saturated fat on the health

Saturated fats

Arteriosclerosis


Reception and sterilisation: • Fresh Fruit Bunches are

weighed, recorded and steamed to kill microbes and

soften the fruits.

Separation of fruits: • Separated fruits are sent for

extraction and purification of oil while the bunches are incinerated.

Extraction and purification Extraction: • Fruits are heated (65-90 °C) so that mesocarp to come loose from the seed. • The seeds are softened to separate the kernel from the hard shell. • The mesocarp is crushed and fed into a presser where the oil is extracted under

high hydraulic pressure (crude palm oil). • Kernel is dried and used or extracting kernel oil (palm kernel oil). Purification: • Crude oil is filtered to remove pieces of shell fibre and other contaminants. • Stem is passed through the palm oil to remove any odour and acid. • Oil is passed through activated carbon to decolourise it.

The extraction of palm oil


Kernel • White in colour • Produces kernel oil

Shell (endocarp) • Hard • Does not produce oil

Pulp (mesocarp) • Thick layer • Orange-reddish in

colour when ripe • Produces the largest

amount of oil

The structure of the oil palm fruit

- consists of mesocarp, shell and kernel


Nutritional substances in palm oil and their benefits

• High Vitamin E (tocopherol, an antioxidant for the prevention of cancer) • Rich in Vitamin A (good vision and lungs) • Cholesterol free • Increase HDL but decrease LDL • Balanced composition of saturated and unsaturated fats (Easy to digest) • Contains carotene, an antioxidant to prevent cancer

The uses of palm oil

• Printing ink • Margarine • Cooking oil • Cocoa butter fibre materials • Soap and detergent • Candle • Lubricating oil • Biodiesel


• Step 1: Fats + water Fatty acids + Glycerol (Hydrolysis of fats)

• concentrated alkalis such as sodium hydroxide acts as catalyst

• Step 2: Common salt (sodium chloride) is added to the solution to make the soap solidify and float on the

surface of the solution.

• Sodium ions combine with fatty acid to form fatty acid salt (soap)

• Sodium ions + Fatty acid --------> Soap (Salt of fatty acid) + water

• The mixture is filtered with filter paper

• The residue (soap) is rinsed with water and dried

Saponification

Oil + Sodium hydroxide Sodium salt of fatty acid (soap) + glycerol + water


• Soap can be dissolved in water to produce bubbles, remove oil and grease.

• A thin firm of soap is formed on the surface of the water. This lowers the surface tension of the water.

• When soap comes in contact with oil or grease. Hydrocarbon chains dissolve in the oil or grease, whereas the ionic ends remain dissolved in water.

• The washing and scrubbing break up the grease from the cloth into small droplets and then rinsed off.

Molecular structure of soap

Attract to water Repel water

How does soap work?


A polymer -a large molecule consisting of a long chain or combination of many units of small molecules

(monomers)

Natural polymer Synthetic polymer

• Exist naturally • Originate from living organisms • Examples: Carbohydrates, proteins, starch,

cellulose, natural rubber

• Man-made polymers • Made from petroleum and natural gas • Examples: Perspex, nylon, PVC, neoprene, butyl rubber,

polystyrene, polythene


Polymer Monomer

Starch Glucose

Protein Amino acid

Rubber Isoprene

Polythene Ethene


Characteristics of natural rubber

• Natural rubber is a natural polymer derived from the rubber tree. • Natural rubber is a polymer composed of the isoprene monomer.

Natural rubber

• Monomer-Isoprene • Elastic- able to return to the original form after being stretched • Poor heat conductor • Good electrical insulator-does not allow electricity to flow through it • Insoluble in water • Not heat-resistant (low melting point)

• Soft and sticky when heated and becomes hard and brittle when cold


• Polymers are enveloped in a layer of protein membrane with negative charges on its surface. These charges repel one another. Thus the latex does not coagulate

• Latex left in collecting cups overnight will eventually solidify because acids produced by bacteria in the latex cause the latex to coagulate. To prevent auto coagulation, ammonia solution is added to latex to neutralize the acids produced by bacteria.

• In industry, acids are added to latex to cause coagulation. Positively charges ions will neutralise the negatively charges of the protein membrane

• Rubber molecules can come close and collide with each other. As a result, protein membrane bursts and set the rubber polymers in it free

Action of acid and alkali in latex


Natural rubber is elastic but when pulled or stretched for a long period of time, the rubber molecules cannot go back to

the previous state. Therefore, it is inappropriate to use natural rubber to make tyres.

• Vulcanisation is carried out by soaking dry natural rubber in sulphur chloride and methyl benzene solution • Cross-links between the natural rubber molecules are formed • Vulcanised rubber becomes stronger, more heat-resistant and more elastic • Goods made from vulcanised rubber - Vehicle tyres, raincoat, gloves, water hoses, insulator of wires

Vulcanisation of rubber

Properties Natural rubber Vulcanised rubber

Elasticity Elastic More elastic

Hardness Soft Harder and stronger

Strength Less powerful More powerful

Resistance to heat Not heat-resistant More heat-resistant


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Form 5 Science Chapter 4: Carbon compounds