GCSE Chemistry - Evolution of the Atmosphere #67

The video explains the evolution of Earth's atmosphere, starting with volcanic activity that created a carbon dioxide-rich environment. Over billions of years, photosynthesis by algae and plants reduced CO2 levels and increased oxygen, enabling complex life. Carbon was sequestered in sedimentary rocks and fossil fuels, shaping today's atmosphere of mostly nitrogen and oxygen.

What is the primary composition of Earth's current atmosphere?

• 80% oxygen, 20% nitrogen

• 80% nitrogen, 20% oxygen

• 50% nitrogen, 50% oxygen

• 70% carbon dioxide, 30% oxygen

What process allowed carbon dioxide to dissolve in the oceans?

• Volcanic eruptions

• Formation of sedimentary rocks

• Photosynthesis

• Condensation of water vapor

How did algae and green plants affect the atmosphere?

• They reduced carbon dioxide and increased oxygen levels.

• They decreased oxygen levels.

• They increased carbon dioxide levels.

• They had no effect on the atmosphere.

What is coal primarily made from?

• Dead plankton

• Calcium carbonate

• Dead plant material

• Volcanic ash

Which substance is formed from the calcium carbonate of marine organisms?

• Crude oil

• Natural gas

• Coal

• Limestone