4.6 Notes
“What are fossil fuels?”
Objective: Describe how coal, oil, and natural gas were formed.
Fossil fuels are fuels that were
formed from fossils. Fuel may be
a solid, liquid, or gas. Fuel gives
off energy when it is burned.
Coal, natural gas, petroleum are
fossil fuels. Most of the energy
that heats our homes comes from
fossil fuels.
Fossil fuels are made up of hydrocarbons. Hydrocarbons are
compounds made of the elements hydrogen and carbon.
Hydrocarbons store energy from the sunlight absorbed by plants
and microorganisms that lived millions of years ago.
Hydrocarbons give off this energy as light and heat when burned.
What two forms of energy are given off when hydrocarbons are
burned?
Coal is formed from sediments and dead plants in swamps.
Bacteria, pressure, and heat cause chemical changes to take place
in the plants. The decaying plant changes to peat. After a long
time, peat changes to soft coal. Pressure changes soft coal into
hard coal.
Stages in coal formation:
Peat
Soft coal
Hard coal
What are the three basic stages of coal formation?
Petroleum and natural gas were formed from decaying
microorganisms. Petroleum and natural gas were formed by the
actions of bacteria, heat, and pressure.
Petroleum is usually found in pools
that collect in layers of shale or
sandstone. If natural gas is
present, it is on top of the oil, or
petroleum. We have to drill into
Earth’s crust to get oil and natural
gas.
What types of ancient organisms formed oil and natural gas?