Grade 12 Chemistry Unit 5 : Introduction to Environmental Chemistry

This unit, “Introduction to Environmental Chemistry,” shows you how chemistry shapes the air you breathe, the water you drink, and the land you live on. You will explore the four components of the environment, the natural cycles that move chemicals through them, the causes and effects of air, water, and land pollution, the chemistry behind global warming, and the modern principles of green chemistry and cleaner production.

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Chapter 5.1 – Introduction to Environmental Chemistry

This opening chapter sets the foundation for the whole unit.

• Definitions: Define environmental chemistry and key terms such as pollutant, contaminant, sink, biological oxygen demand (BOD), and Threshold Limit Value.
• Components of the Environment: Describe the four components — atmosphere, hydrosphere, lithosphere, and biosphere — and the important reactions in each.
• Natural Cycles: Explore the hydrological, carbon, nitrogen, oxygen, sulfur, and phosphorus cycles and how they keep the environment in balance.
• Multidisciplinary View: Understand why environmental chemistry connects with biology, geology, physics, and ecology.

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Chapter 5.2 – Environmental Pollution

This chapter examines the three main types of pollution.

• Air Pollution: Identify major air pollutants (CO, SO₂, NOₓ, particulates) and discuss their sources, effects, and acid-rain chemistry.
• Water Pollution: Describe water pollutants, BOD, eutrophication, heavy metals, and the impact on aquatic life.
• Land Pollution: Analyze causes of land pollution from solid waste, pesticides, and plastics.
• Control Methods: Apply the main methods used to reduce air, water, and land pollution in Ethiopian and global contexts.

Chapter 5.3 – Global Warming and Climate Change

This chapter explains the chemistry behind the climate crisis.

• Greenhouse Effect: Describe global warming and climate change from a chemistry viewpoint and explain the greenhouse effect.
• Greenhouse Gases: List the common greenhouse gases (CO₂, CH₄, N₂O, water vapour, CFCs, O₃) and compare their atmospheric lifetime and warming contribution.
• Chemistry of Climate Change: Discuss the chemical reactions of greenhouse gases in the atmosphere and classify them by source (anthropogenic vs natural).

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Chapter 5.4 – Green Chemistry and Cleaner Production

This final chapter introduces the modern, sustainable approach to chemistry.

• Definitions: Define green chemistry and cleaner production.
• The 12 Principles: Discuss the major principles of green chemistry and the importance of cleaner production.
• Atom Economy: Explain atom economy and calculate it for a given chemical reaction.
• Application: Apply green-chemistry principles when designing reactions and doing laboratory experiments.

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Learning Outcomes

By the end of this unit, you will be able to:

• Define environmental chemistry and describe the four components of the environment along with their natural cycles.
• Identify air, water, and land pollutants, and explain their causes, effects, and control methods.
• Explain the greenhouse effect and describe how greenhouse gases drive global warming and climate change.
• Apply the principles of green chemistry and calculate atom economy for chemical reactions.