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

• $Carbon Dioxide + Water \xrightarrow{Light} Glucose + Oxygen$

Formation of Oceans and Carbonates

• 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

1. Getting the raw materials (mining, farming, forestry, etc.).
2. Manufacturing & production (energy and water used; waste produced).
3. Distribution (how the product is used and if it produces pollution).
4. 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.