5.3 — Alcohol

Definition and Preparation

• Alcohol is an organic carbon compound containing carbon, hydrogen and oxygen.
• Alcohol is prepared by fermentation: yeast acts on food containing glucose or starch, such as sugar, grapes, apples, sugarcane, rice, wheat, potatoes and barley.
• During fermentation, the zymase enzyme in yeast converts glucose into ethanol and carbon dioxide.

Activity 5.5 — Preparing ethanol through fermentation

• Materials: distilled water, yeast, sugar, starchy substances such as bread and rice, fruits such as banana and apple, porcelain chips and limewater.
• Apparatus: beaker, glass rod, conical flask, measuring cylinder, delivery tube with stopper, test tube, distillation flask, Liebig condenser, thermometer, Bunsen burner, tripod stand and wire gauze.

Fermentation set-ups

• A—sugar: dissolve 100 g sugar in 50 cm³ distilled water; add 10 g yeast.
• B—starch: mix 100 g bread with 50 cm³ distilled water; add 10 g yeast.
• C—fruit: mix 100 g mashed banana with 50 cm³ distilled water; add 10 g yeast.
• Transfer each mixture into a conical flask connected by a delivery tube to limewater; keep for one week.
• Carbon dioxide produced during fermentation turns limewater cloudy.

Obtaining ethanol

1. Filter the fermented mixture and transfer the filtrate into a distillation flask with porcelain chips.
2. Distil using a water-cooled Liebig condenser.
3. Collect the distillate at 78°C.
4. Distillation separates ethanol because ethanol and water have different boiling points.

Physical and Chemical Properties

Physical properties of alcohol

• Colourless.
• Liquid at room temperature.
• Has a distinctive smell.
• Volatile.
• Boiling point increases as the number of carbon atoms increases.
• Solubility in water decreases as the number of carbon atoms increases.

Activity 5.6 — Properties of ethanol

A. Physical properties

• Observe ethanol’s colour, state at room temperature, smell and solubility in water.

B. Combustion

1. Ignite 2 cm³ ethanol in an evaporating dish.
2. Observe the flame.
3. Pass the released gas into limewater to test for carbon dioxide.
4. Test liquid droplets on a filter funnel using dry cobalt chloride paper to identify water.

C. Esterification

1. Mix 2 cm³ ethanol with 2 cm³ ethanoic acid in a boiling tube.
2. In a fume chamber, add five drops of concentrated sulphuric acid and shake.
3. Heat for several minutes, then pour the mixture into water.
4. Esterification between ethanol and ethanoic acid produces an ester; concentrated sulphuric acid acts as a catalyst.

Safety: Concentrated sulphuric acid is highly corrosive; handle it only in a fume chamber.

Uses of Alcohol in Daily Life

Field	Use
Fuel	A highly flammable fuel that burns with a blue flame; complete, clean combustion produces no soot. Alcohol is used as a motor-vehicle biofuel in the Philippines.
Medicine	Antiseptic and disinfectant that kill microorganisms; solvent for various medicines.
Cosmetics	Solvent in perfume, lotion and lipstick.
Industry	Solvent for organic substances in products such as liquid cleaners and food; reactant for esters used in food processing, cosmetics and paint. Ethanediol is used as antifreeze.

Effects of Excessive Alcohol Consumption

• Causes addiction, family and social problems, crime, dangerous driving and altercations.
• Excessive consumption during pregnancy can cause foetal alcohol syndrome: small head and brain, abnormal face and stunted growth.

Part of body	Adverse effect
Brain	Brain-cell damage; compromised coordination and nervous system; disturbed balance and difficulty estimating distance
Eyes	Blurred vision
Lungs	Increased breathing rate
Heart	Increased heartbeat and high blood pressure
Stomach	Irritated stomach wall, bleeding and ulcers
Liver	Damaged liver cells; cells die and harden; cirrhosis and liver cancer
Kidney	Damage from overactive elimination of waste substances
Urinary bladder	Frequent urination