Lesson Notes By Weeks and Term v3 - Junior Secondary 2
Crude oil and Petrochemicals
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Crude oil and Petrochemicals
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Subject: Basic Science
Class: Junior Secondary 2
Term: 3rd Term
Week: 8
Theme: Science And Development
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Explain what Crude oil and petrochemicalsare Describe the process of refining crudeoil; State the uses of crude oil and petrochemicals State the importance of crude oil to Nigeria
Definition: Crude oil, also known as petroleum, is a naturally occurring, yellowish-black liquid found beneath the Earth's surface. It is a fossil fuel, formed from the decomposition of dead marine organisms (plants and animals) over millions of years under immense heat and pressure.
Composition: Crude oil is primarily a complex mixture of various hydrocarbons (compounds made of hydrogen and carbon atoms) of different sizes and structures, along with smaller amounts of other elements like sulfur, nitrogen, and oxygen.
Properties: It is a viscous (thick), flammable liquid with a distinctive odour, and its colour can vary from light yellow to dark black, depending on its composition. It is insoluble in water.
Occurrence in Nigeria: Nigeria is a major crude oil producer, with significant reserves primarily located in the Niger Delta region.
Definition: Petrochemicals are chemical products derived from petroleum (crude oil) or natural gas. They are essentially the "building blocks" that are further processed to create a vast array of useful materials and products.
How they are formed: During the refining of crude oil, certain fractions (like naphtha) are separated and then chemically processed (e.g., cracking, reforming) to produce basic petrochemicals. These basic petrochemicals are then used as raw materials for a wide range of industries.
Examples of basic petrochemicals: Ethylene, propylene, butadiene, benzene, toluene, and xylene. These are fundamental compounds from which many other chemicals are synthesized. Crude oil is not directly usable in its raw form because it is a mixture of many different hydrocarbons with varying properties. It must be refined to separate it into more useful components or "fractions." The primary method for this separation is fractional distillation.
Steps involved in Fractional Distillation: Heating: The raw crude oil is first heated in a large furnace to a very high temperature, typically around 350-400°
C. This causes most of the crude oil to vaporize (turn into gas).
Fractionating Column: The hot mixture of liquid and vapour is then pumped into the bottom of a tall, cylindrical structure called a fractionating column or distillation tower.
Temperature Gradient: The fractionating column has a temperature gradient: it is hottest at the bottom and gradually cooler towards the top.
Vapour Rise and Condensation: As the hot vapours rise up the column, they begin to cool. Different hydrocarbons (fractions) have different boiling points. Fractions with higher boiling points (heavier molecules) condense at lower levels (hotter parts) of the column and are collected as liquids. Fractions with lower boiling points (lighter molecules) continue to rise higher up the column (cooler parts) before they condense and are collected. The lightest fractions with the lowest boiling points remain as gases and are collected at the very top.
Collection of Fractions: Trays or plates at different levels collect the condensed liquid fractions. Each fraction is a mixture of hydrocarbons with similar boiling points and properties. Major Fractions and their Boiling Points/Uses (from bottom to top of column): | Fraction | Boiling Point Range (°C) | Typical Uses in Nigeria | | :----------------------- | :----------------------- | :--------------------------------------------------------------- | | Bitumen/Asphalt | >350 | Road surfacing (tar), roofing | | Fuel Oil | 300-350 | Fuel for ships, power stations, industrial furnaces, generators | | Lubricating Oils | 250-300 | Lubricants for engines, machinery | | Diesel Oil (Gas Oil) | 200-250 | Fuel for diesel engines (trucks, buses, generators), heating oil | | Kerosene (Paraffin) | 150-200 | Fuel for jet engines, domestic cooking, lighting, solvents | | Naphtha | 70-150 | Raw material for petrochemicals (plastics, fertilizers) | | Gasoline (Petrol) | 40-70 | Fuel for cars, motorcycles, small generators | | Refinery Gases (LPG) | <40 | Bottled gas (cooking gas), chemical feedstock, power generation | Nigerian Context: Nigeria has several crude oil refineries (e.g., Port Harcourt Refinery, Warri Refinery, Kaduna Refinery), which perform this fractional distillation process.
A. Uses of Crude Oil Fractions (Direct Products of Refining): Fuel: Petrol (Gasoline): Powers cars, motorcycles, and small generators.
Diesel: Powers heavy vehicles (trucks, buses), trains, larger generators, and some industrial machinery.
Kerosene: Used for domestic cooking, lighting lamps, and as aviation fuel (jet fuel).
Fuel Oil: Used in industrial furnaces, power plants, and marine vessels.
Liquefied Petroleum Gas (LPG): Bottled gas for domestic cooking and heating.
Lubricants: Motor oils, greases, and industrial lubricants derived from crude oil fractions reduce friction in engines and machinery.
Asphalt/Bitumen: Used for paving roads and roofing materials due to its waterproofing properties.
B. Uses of Petrochemicals (Derived Products): Petrochemicals are the raw materials for an enormous range of products: Plastics: Polyethylene (plastic bags, bottles, pipes), polypropylene (containers, car parts), PVC (pipes, window frames), polystyrene (packaging, disposable cups).
Synthetic Fibres: Polyester, nylon, acrylics are used to make clothing, carpets, ropes, and other textiles.
Fertilizers: Ammonia-based fertilizers (e.g., urea) crucial for agriculture to boost crop yields.
Detergents: Used for washing clothes, dishes, and general cleaning.
Paints and Coatings: Used to protect and decorate surfaces.
Pharmaceuticals: Many medicines and drugs have petrochemicals as starting materials.
Solvents: Used in industries, paints, and cleaning agents.
Synthetic Rubber: Used for tyres, conveyor belts, and various rubber products.
Pesticides and Herbicides: Chemicals used in agriculture to protect crops.
Cosmetics and Toiletries: Ingredients in perfumes, lotions, and soaps.
Economic Dependence and Stability: Teachers can facilitate a discussion on how global crude oil prices directly impact Nigeria's economy. When prices fall (e.g., during a global economic downturn), government revenue shrinks, affecting budget implementation, infrastructure projects, and even salaries. Conversely, rising prices can boost the economy. This helps students understand national economic realities and the importance of diversification.
Everyday Products and Consumer Choices: Students can be asked to identify plastic items (water bottles, bags, utensils), synthetic clothing (polyester shirts), cleaning agents (detergents), and even some medicines they use daily, linking them back to crude oil derivatives (petrochemicals). This illustrates the pervasive role of petroleum in modern life and can spark discussions about responsible consumption and recycling.
Environmental Impact and Sustainability: While the lesson focuses on importance, it is crucial to briefly touch upon the environmental consequences of crude oil exploration and processing in Nigeria. Discussing issues like oil spills in the Niger Delta, gas flaring (which contributes to air pollution and climate change), and their effects on local communities (fishing, farming) can integrate environmental literacy and encourage critical thinking about sustainable practices and alternative energy sources.