Coal and Petroleum

Coal tar

Step 1: Coal when processed gives three main products — coke, coal tar, and coal gas. Step 2: Coal tar is a black, thick liquid that is a mixture of about 200 substances. Step 3: Many useful everyday products are made from substances found in coal tar, including synthetic dyes, drugs, explosives, perfumes, plastics, and paints. Step 4: Naphthalene balls, which are placed in cupboards and wardrobes to repel moths and insects, are also obtained from coal tar. Step 5: Coke is used in steel making, coal gas is used as fuel — neither is used to make naphthalene balls.

Rock and oil

Step 1: The word petroleum comes from two Latin roots: 'petra' meaning rock and 'oleum' meaning oil. Step 2: Together, petroleum means 'rock oil' because it is found trapped between rocks beneath the Earth's surface. Step 3: Petroleum is extracted by drilling wells into these rock layers. Step 4: 'Black and gold' refers to petroleum's nickname 'black gold' because of its great commercial importance — but that is not the origin of the word. Step 5: Understanding word origins helps us remember that petroleum is naturally found within rocky layers underground.

From organisms living in the sea whose dead bodies got covered with sand and clay at the sea bottom

Step 1: Petroleum was formed from tiny organisms (plants and animals) that lived in ancient seas millions of years ago. Step 2: When these organisms died, their bodies settled at the bottom of the sea. Step 3: Over time, layers of sand and clay covered these dead bodies. Step 4: Over millions of years, in the absence of air, under high temperature and high pressure, these dead organisms were transformed into petroleum and natural gas. Step 5: Coal, on the other hand, was formed from dead forests on land — this is an important difference between coal and petroleum formation.

Natural gas is lighter than both oil and water, so it rises to the top

Step 1: In a petroleum deposit underground, three layers are found — water at the bottom, petroleum oil in the middle, and natural gas at the top. Step 2: The arrangement depends on the density (heaviness) of each substance. Step 3: Water is the heaviest, so it settles at the bottom. Oil is lighter than water, so it floats above water. Natural gas is the lightest of all, so it rises to the top. Step 4: This is the same principle we see when oil floats on water in our kitchen. Step 5: Natural gas does not mix with oil or water — it stays as a separate layer at the top due to its low density.