Understanding Mechanical Properties and Ferrous Materials
Mechanical Properties
Elasticity: The capacity of a material to regain its original shape after being stretched.
Plasticity: The capacity of a material to retain its new shape after being deformed.
Ductility: The capacity of a material to be stretched into wires.
Malleability: The capacity of a material to be spread into sheets.
Hardness: The opposition a body offers to being scratched or penetrated by another.
Fragility: The opposite of tenacity. It is the tendency of a body to break under stress.
Resilience:
Read MoreContinental Drift and Plate Tectonics: Earth’s Shifting Surface
Item 4: Earth’s Dynamic Crust
Introduction
The movement of the Earth’s crust (lithosphere) is continuous.
The Theory of Continental Drift
In 1912, Alfred Wegener, a German meteorologist, gathered a large amount of geological, paleontological, and climatic data. These data indicated that the continents had moved through time. Wegener showed that all the continents were once united into a single supercontinent called Pangaea. Pangaea later fragmented into several continents that drifted to their present
Read MorePre-Socratic Philosophers: From Myth to Reason
Key Features of Pre-Socratic Thought
- Replacing Myth with Reason: Pre-Socratic philosophers replaced mythical narratives with rational explanations.
- Order in the World: They sought to give the world a necessary order, moving away from the idea that tragic things occur arbitrarily.
- Focus on *Physis* and *Arche*: They focused on *physis* (nature) and the *arche* (the fundamental principle or origin of everything).
- Discovering Truth: The scientist discovers what is behind phenomena, and the principle that
Understanding Biogeochemical Cycles: Carbon, Nitrogen, Phosphorus, and Sulfur
Biogeochemical Cycles
Biogeochemical cycles describe the exchange of certain chemical elements between the organisms that form the biocenosis and the biota.
Carbon Cycle
Carbon is the most abundant chemical element in all living things. It is located in the atmosphere, dissolved in water, in carbonate rocks, and in the form of fossil fuels.
- Through photosynthesis, autotrophic organisms convert atmospheric CO2 into organic matter, which is used to feed animals.
- During respiration, organic matter is consumed,
Air and Noise Pollution: Causes, Effects, and Solutions
What is Air Pollution?
Air pollution is the release into the air of substances in solid, liquid, or gas form, or energy (heat, noise, radiation), altering its natural composition and posing risks, harm, or serious problems to people, ecosystems, and property of any nature.
Understanding Smog Formation
Smog forms due to the concentration of air pollutants released primarily in metropolitan areas by industrial activities, heating, and traffic. In the accompanying drawing, the source of the smog is mainly
Read MoreEarth’s Geological Timeline: From Hadean to Today
Earth’s Geological Timeline: 4.65 Billion Years of History
Geological Time Divisions
Earth’s existence spans approximately 4,650 million years (Ma). The largest unit of geological time is the eon. There are two great eons:
- Precambrian: Comprises 90% of Earth’s history.
- Phanerozoic: Divided into three eras: Paleozoic, Mesozoic, and Cenozoic.
These eras are further divided into periods. The Cenozoic era, for instance, is divided into the Tertiary and Quaternary periods.