Earth Science Lecture Review
Structure of Earth
- Crust: Solid, broken into tectonic plates.
- Mantle: Behaves like a slow-moving fluid; convection currents drive plate tectonics.
- Outer core: Liquid.
- Inner core: Solid.
Composition of Earth's Atmosphere
- Nitrogen: N_2 = 78\%
- Oxygen: O_2 = 21\%
- Argon: Ar = 0.9\%
- Carbon Dioxide: CO_2 = 0.04\%
- Early atmosphere (first billion years): intense volcanic activity released gases, including large amounts of water vapor, carbon dioxide, some methane, and ammonia.
Evolution of Oxygen Levels
- Initially low; increased approximately 2.7 billion years ago.
- Evolution of algae and plants led to oxygen production via photosynthesis.
Photosynthesis
- Carbon Dioxide + Water \xrightarrow{Light} Glucose + Oxygen
- Water vapor condensed to form oceans.
- Some oxygen dissolved in oceans, forming weak acids.
- These acids reacted to form carbonate precipitates, which became sediments (e.g., limestone).
- Shells and skeletons of marine organisms (e.g., mussels) also contributed to sedimentary carbonate rocks.
Greenhouse Effect
- Greenhouse gases (water vapor, carbon dioxide, methane) trap heat, keeping Earth warm enough to support life.
- Energy from the sun reaches Earth as short-wavelength radiation.
- Some radiation is reflected back into space but must pass through the atmosphere.
- The Earth's surface absorbs the remaining energy and re-emits it as long-wavelength radiation.
- Greenhouse gases absorb the long-wavelength radiation, trapping energy and warming the planet.
Anthropogenic Climate Change
- Human activities (burning fossil fuels, farming, and deforestation) increase greenhouse gas concentrations.
- This leads to global warming and climate change.
- Consequences include extreme weather events, rising sea levels, melting ice caps, and habitat loss.
Combustion
- Combustion: A chemical process that involves rapid reaction between a substance with an oxidant, usually oxygen, to produce heat and light.
Pollutants produced from Combustion
- Carbon dioxide: A greenhouse gas contributing to global warming.
- Particulates (soot): Tiny particles that can cause respiratory problems.
- Sulfur dioxide: Contributes to acid rain.
- Nitrogen oxides: Contribute to respiratory problems and acid rain.
Complete Combustion
- Occurs when there is plenty of oxygen.
- Produces carbon dioxide and water, releasing more energy.
- Fuel + Oxygen \rightarrow Carbon Dioxide + Water + Energy
Incomplete Combustion
- Occurs when oxygen is limited.
- Produces carbon monoxide (toxic gas), soot (carbon), and less energy.
- More polluting and dangerous.
- Fuel + Oxygen \rightarrow Carbon Monoxide + Carbon + Water + Energy
Fuels
- Substances containing stored chemical energy that is released during combustion by reacting with oxygen.
- Examples: Coal, oil, natural gas.
Life Cycle Assessment Stages
- Getting the raw materials (mining, farming, forestry, etc.).
- Manufacturing & production (energy and water used; waste produced).
- Distribution (how the product is used and if it produces pollution).
- Product Disposal (what happens when the product is discarded).
Purpose of Life Cycle Assessments
- To compare products and identify ways to reduce their environmental impact.
- To ensure companies make environmentally conscious choices.
Issues with Life Cycle Assessments
- Can be complex and difficult to conduct comprehensively.
- Incomplete data may lead to inaccurate assessments.
Reduce, Reuse, Recycle
- Reduce: Use less in the first place, buy fewer disposable products or use items with less packaging to reduce demand, production, raw materials, energy use, landfill waste, and pollution.
- Reuse: Use things again such as refill water bottles, reusable bags, or donate old clothes to extend the life of a product and reduce the need for new materials and environmental impact.
- Recycle: Break down waste materials to make new products like paper, glass, plastic, and metal; reduces pollution, cuts down on raw material and energy use, and landfill waste.
Ceramics
- Non-metallic solids with high melting points that are not made from carbon-based compounds.
- Soda-lime glass: Sand + sodium carbonate + limestone. Mixed in a furnace until melted, shaped, and solidified. Used for windows and glass.
- Borosilicate glass: Sand + boron trioxide for ovenware and lab ware.
- Clay: Mineral found in the ground; when wet, it can be molded and hardened by firing.
Composites
- Made by combining two different materials.
- Mixture of matrix/binder material surrounds the reinforcement.