Earth's Atmosphere & Climate Change
The Earth's atmosphere has evolved over 4.6 billion years from a carbon-dioxide-rich volcanic atmosphere to today's mixture of approximately 78% nitrogen and 21% oxygen. In recent centuries, human activities such as burning fossil fuels, deforestation, and agriculture have increased atmospheric concentrations of greenhouse gases, driving global climate change.
- Photosynthesis
- The process by which plants and algae use sunlight to convert carbon dioxide and water into glucose and oxygen.
- Greenhouse Gas
- Gases in the atmosphere that absorb outgoing long-wavelength radiation, such as carbon dioxide, methane, and water vapour.
- Carbon Footprint
- The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service, or event.
Earth's Atmosphere & Climate Change: Reaction Profile (ΔH & E_a) + Le Chatelier Yield Simulator
Toggle a catalyst on the enthalpy profile diagram or adjust temperature and pressure to see how dynamic equilibrium shifts.
Modelled on N₂(g) + 3H₂(g) ⇌ 2NH₃(g) (ΔH = −92 kJ/mol) (4 moles gas → 2 moles gas):
Higher pressure shifts equilibrium to the side with fewer gas moles (right, 4 → 2). Lower temperature favours the exothermic forward reaction.
Key Concepts & Exam Definitions (5)
- Photosynthesis
- The process by which plants and algae use sunlight to convert carbon dioxide and water into glucose and oxygen.
- Greenhouse Gas
- Gases in the atmosphere that absorb outgoing long-wavelength radiation, such as carbon dioxide, methane, and water vapour.
- Carbon Footprint
- The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service, or event.
- Acid Rain
- Rain containing higher concentrations of hydrogen ions (low pH) caused by emissions of sulfur dioxide and nitrogen oxides.
- Global Warming
- The long-term heating of Earth’s climate system observed due to human activities, primarily fossil fuel burning.
Quick-Fire Flashcards (5)
Click any card to check the answer, then mark it as Known to track your progress.
Which gas makes up the majority of the Earth’s atmosphere?
What caused carbon dioxide levels to decrease in the early atmosphere?
Name three greenhouse gases.
What is a major source of atmospheric methane?
What problem does sulfur dioxide cause?
Exam-Style Questions & Mark Schemes (3)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
Explain how the greenhouse effect works to keep the Earth warm.
Click “Check Mark Scheme” to compare your answer, Short-wavelength radiation from the sun passes through the atmosphere and hits the Earth. The Earth radiates it back as long-wavelength thermal radiation, which is absorbed by greenhouse gases, trapping heat in the atmosphere.
- Q2
Describe two ways humans can reduce their carbon footprint.
Click “Check Mark Scheme” to compare your answer, Using renewable energy sources instead of fossil fuels, and improving energy efficiency in homes and transport.
- Q3
How is carbon monoxide formed during combustion, and why is it dangerous?
Click “Check Mark Scheme” to compare your answer, It is formed by incomplete combustion (lack of oxygen). It is a toxic, colourless, and odourless gas that binds to haemoglobin in red blood cells, preventing them from carrying oxygen.
Common Exam Questions (3)
What is the current composition of the Earth’s atmosphere?
Dry air in the modern atmosphere consists of approximately 78% nitrogen (N₂), 21% oxygen (O₂), nearly 1% argon, and about 0.04% carbon dioxide (CO₂), along with variable amounts of water vapour.
How did oxygen increase in the early atmosphere?
Photosynthetic algae evolved around 2.7 billion years ago, followed by green plants. Photosynthesis absorbed carbon dioxide and released oxygen into the atmosphere, gradually building up O₂ levels so complex animals could evolve.
What is the greenhouse effect?
Greenhouse gases (water vapour, carbon dioxide, and methane) allow short-wavelength radiation from the Sun to pass through the atmosphere to warm the Earth's surface, then absorb and re-emit outgoing long-wavelength infrared radiation, keeping the lower atmosphere warm.
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