Fossil fuel — Science definition

Defined in 2 courses:

A nonrenewable energy resource — coal, oil, or natural gas — formed from the buried remains of ancient organisms transformed by heat and pressure over millions of years. (Physics & Environmental Science)
A carbon-rich energy source — coal, oil, or natural gas — formed from the buried remains of ancient organisms, storing carbon that had been out of the active cycle for millions of years. (Physics & Environmental Science)

Where it is taught

Natural Resources: Renewable & Nonrenewable — Resources & Human Decisions, Earth & Space Science, Grade 9
Nonrenewable Energy & Fossil Fuels — Energy, Water & Material Resources, Physics & Environmental Science, Grade 12
Climate Change — Pollution, Carbon & Climate Evidence, Physics & Environmental Science, Grade 12

Questions using fossil fuel

Problem 1

Why is fossil fuel nonrenewable on a human planning timescale?

Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Formation takes geological timescales compared with rapid extraction and use.

Problem 2

Which of the following is a fossil fuel?

Wind
Coal
Uranium
Sunlight

Answer and explanation

Coal

Coal, oil, and natural gas are the three fossil fuels. Uranium is a nuclear fuel, and sunlight and wind are renewable.

Problem 3

Which fossil fuel typically releases the LEAST carbon dioxide per unit of energy when burned?

Coal
Oil (petroleum)
Natural gas
Peat

Answer and explanation

Natural gas

Natural gas emits roughly half the CO2 of coal per kilowatt-hour, which is why it is often called a 'cleaner' fossil fuel.

Problem 4

Natural gas is often called a 'cleaner' fossil fuel than coal, yet scientists warn that its climate benefit can be undercut. Explain why, using the term methane.

Answer and explanation

Burning natural gas releases only about half the CO2 of coal per unit of energy, which is the source of its 'cleaner' reputation. But natural gas is mostly methane, a powerful greenhouse gas, and some of it leaks unburned into the atmosphere during drilling, storage, and transport. Because methane traps far more heat than CO2 (especially in the short term), those leaks can cancel out much of the CO2 advantage.

Taught alongside

Elsewhere

Browse all courses