CHEM_142_Lecture_1

CHEM 142: The Global Impact of Chemistry for Engineering

Greenhouse Effect Overview

• Definition & Concepts: Understanding the Greenhouse Effect is crucial for grasping its impact on climate change and global warming.

  • This encompasses studying the chemical concepts associated with greenhouse gases (GHGs), such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).

  • Students will also learn the fundamentals of light, which includes properties such as wavelength, frequency, and energy, all of which play a role in how various substances interact with solar radiation.

• The Sun's Contributions:

  • The Sun is essential as it provides not only light but also Vitamin D, energy, and heat that are critical for sustaining life on Earth.

  • Its surface temperature is approximately 6000 K, which is a vital component in understanding the radiation balance of the Earth.

The Greenhouse Effect Mechanism

• The process begins with the Sun emitting light; a significant portion of this light reaches the Earth's surface.

• As Earth absorbs this sunlight, it re-emits some of it back into space in the form of infrared radiation.

• Certain atmospheric gases effectively absorb and trap this re-radiated light, leading to a gradual increase in planetary temperatures, which is a central concern in discussions about climate change.

Global Temperature Trends

• Historical Data (1850-2018):

  • Detailed data illustrates increasing temperature anomalies since 1850, with significant variations compared to the 1951-1980 average.

  • Graphical representations will be used in class to depict the global temperature variations through this period.

• Latest Data:

  • In 2023, the latest annual average anomaly was measured at 1.17 °C (or 2.11°F) above the historical averages, providing critical evidence of ongoing climate change.

  • Multiple data sources consistently indicate rising temperatures over recent decades, reinforcing the urgency of addressing global warming.

Carbon Dioxide (CO2) & Methane (CH4)

• CO2 Levels:

  • As of July 2023, the concentration of CO2 in the atmosphere was recorded at 422 ppm (parts per million), with one ppm corresponding to one milligram per liter of air.

  • Projections for July 2024 indicate a rise to 426 ppm, underlining the ongoing increase in greenhouse gas emissions.

• Methane Emissions:

  • It is important to note that methane (CH4) is approximately 80 times more potent as a greenhouse gas compared to CO2 over a 20-year period.

  • Recent data indicate a 20% increase in methane emissions over the past 20 years, highlighting its rising significance in the global warming discourse.

Light Interactions with Matter

• Nature of Light:

  • Light is characterized as electromagnetic radiation, which consists of oscillating electric and magnetic fields. This duality is important for understanding its interactions with various materials.

• Wave Properties of Light:

  • Key properties of waves will be covered, including wavelength (λ), defined as the distance between consecutive crests of waves; frequency (ν), which is the number of crests passing a point per unit time; and amplitude, the height of the wave crest or depth of the trough.

• Relationships in Electromagnetic Waves:

  • Wavelength and frequency are inversely proportional, a relationship governed by the equation: c = λν, where c equals the speed of light (≈ 2.998 × 10^8 m/s).

Quantum Theory & Particle Behavior

• Light Quantization:

  • In terms of quantization, light exhibits wave-particle duality, behaving both as a wave and a particle, a concept essential to modern physics.

  • Photons are defined as the quanta of electromagnetic radiation; their energy can be calculated using Planck's constant (E = hν).

• Types of Electromagnetic Radiation:

  • Students will explore familiar types of electromagnetic radiation, such as microwaves, radio waves, X-rays, visible light, and infrared waves, which have applications across various scientific fields.

  • The electromagnetic spectrum illustrates the range of radiation from high-energy gamma rays to low-energy radio waves, enabling students to understand how different wavelengths affect matter and energy transfer.