Energy from the Ancient Past
For the last 150 years, our world has been powered primarily by fossil fuels. These are energy-rich substances that are found underground. The three main types of fossil fuels are coal (a solid), petroleum or oil (a liquid), and natural gas (a gas).
Fossil fuels contain chemical potential energy that was originally captured from the sun by ancient plants and organisms through photosynthesis. When we burn them, we are releasing energy from sunlight that shone on the Earth hundreds of millions of years ago.
How Fossil Fuels Were Formed
Fossil fuels are the remains of ancient life, transformed over an immense amount of time.
1.Life and Death: Millions of years ago, during periods like the Carboniferous Period, the Earth was covered in lush forests and swamps, and the oceans were filled with tiny organisms like plankton and algae. When these organisms died, they sank to the bottom of swamps or oceans.
2.Burial: Layers of sand, silt, and rock buried the dead organic matter. This prevented it from decomposing completely.
3.Heat and Pressure: Over millions of years, the immense heat from the Earth's interior and the pressure from the layers of sediment above cooked and squeezed the organic matter.
4.Transformation: This heat and pressure slowly transformed the organic matter into the substances we know today:
Dead land plants (trees, ferns) in swamps became coal.
Dead marine organisms (plankton, algae) became oil and natural gas.
Non-Renewable Resources
Because this process takes hundreds of millions of years, fossil fuels are considered a non-renewable resource. We are using them up far, far faster than they could ever be naturally replaced. Once we run out, they are gone for good on a human timescale.
The Environmental Impact
While fossil fuels have powered our modern society, burning them has serious consequences for the environment. The process of burning is called combustion.
Air Pollution: Burning fossil fuels, especially coal, can release pollutants like sulfur dioxide, which can cause acid rain.
The Greenhouse Effect and Climate Change: The main product of burning fossil fuels is carbon dioxide (CO₂) , a greenhouse gas. Greenhouse gases act like a blanket in our atmosphere, trapping heat from the sun. While this effect is natural and necessary for life, by burning fossil fuels, we are adding huge extra amounts of CO₂ to the atmosphere. This is making the 'blanket' thicker, trapping more heat, and causing the Earth's average temperature to rise. This is known as global warming, and it is the main driver of modern climate change.