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ENV100Y5 (131)
Chapter 2

Chapter 2.docx

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Department
Environment
Course
ENV100Y5
Professor
Monika Havelka
Semester
Fall

Description
Chapter 2: Matter: all of the material in the universe that has mass and occupies • Law of conversation: it can be transformed from one type of substance into another, but it cannot be destroyed or created • In environmental science it helps us understand that the amount of matter stays constant as it is recycled in nutrient cycles and eco-systems • Plasma: electrically neutral medium of positive and negative particles • Elements: is a fundamental type of matter, a chemical substance with a given set of properties that cannot be broken down into substances with other properties • Atoms: elements are composed of atoms, the smallest components that maintain the chemical properties of that element • Nucleus contains protons (positively charged particles) and neutrons (particles with no electric charge) • Atomic number of element = the number of protons • Electrons = negatively charged particles surrounding the nucleus; balance the positively charged protons • Ion = atom that has gained or lost an electron from its outer shell o Cation = + charge (loses electron) o Anion = ‒ charge (gains electron) • Isotopes: atoms of the same element with differing of neutrons o Mass number = the combined number of protons and neutrons • Example:Atomic number of carbon is 6, so all isotopes of carbon are 6 protons • Molecule = combination of two or more atoms • Example: molecular oxygen = O2 • Example: ozone = O3 • Compound = molecule composed of atoms of two or more different elements • Example: water = H2O • Example: carbon dioxide = CO2 • Solution = mixture without chemical bonding or reactions • Example: crude oil (a mixture of hydrocarbon compounds) • Example: air (a mixture of gases) • Example: ocean water (a mixture of water and dissolved solids) Atoms in molecules and compounds are held together with bonds: • Covalent bond = atoms in a molecule share electrons • Example: hydrogen H2 electrons are shared equally • Polar covalent bonds = electrons are shared unequally, with one atom exerting a greater pull • Example: water H2O electrons unequally distributed • Ionic bonds = an electron is transferred from one atom to another • Example: NaCl (table salt) sodium (Na) gives up an electron, chloride (Cl) takes an electron • Bonding is an outer-shell process (electrons are exchanged or shared) • Fusion, fission, and radioactive decay are nuclear processes Hydrogen ions (H+) determine acidity: • The pH scale quantifies the acidity of solutions o Acidic solutions = pH < 7 o Basic solutions = pH > 7 o Neutral solutions = pH of 7 Organic compounds are made of carbon: • Organic compound = carbon atoms joined by covalent bonds o Often with hydrogen, nitrogen, oxygen, sulphur, phosphorus • Hydrocarbons = contain only carbon and hydrogen o The simplest hydrocarbon is methane o Can be gas, liquid, or solid Macromolecules are building blocks of life: • Polymers = long chains of repeated molecules • Macromolecules = large-size molecules • Many macromolecules are essential to life: o Proteins, nucleic acids (RNAand DNA), carbohydrates, lipids We create synthetic polymers: • Plastics = synthetic (human-made) polymers o Many are derived from petroleum hydrocarbons o Valuable because they resist chemical breakdown o Problematic because they cause long-lasting waste and pollution Energy is conserved but can change form: • Potential energy = energy of position • Kinetic energy = energy of motion • Chemical energy = potential energy in the bonds between atoms The Sun’s energy powers Earth systems: • The Sun emits radiation in the electromagnetic spectrum o Visible light is part of the EM spectrum o Solar energy is modified when it passes through the atmosphere o Solar energy drives weather and climate, and powers plant growth The Sun’s energy powers life: • Autotrophs produce their own food from the Sun’s energy (most commonly) • Heterotrophs obtain energy by eating autotrophs • Photosynthesis = turning light energy from the sun into chemical energy • 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2 Cellular respiration releases chemical energy: • Organisms use chemical energy obtained through photosynthesis • Oxygen is used to convert glucose into water + carbon dioxide + energy o “Reverse photosynthesis” • C6H12O6 + 6O2 → 6CO2 + 6H2O + energy Geothermal energy also powers Earth systems: • Main driver of plate tectonics and volcanism • Hydrothermal vents = heat released from Earth’s interior onto the ocean floor o Host entire communities that thrive in high temperature and pressure on the ocean floor o Chemosynthesis = uses chemical bond energy to produce sugars The time scale of Earth history • Age of Sun and solar system: ~4.57Ga • Based on models of stellar evolution and dating of primitive solar system objects (carbonaceous chondrites/ meteorites) • Age of Earth: ~4.54Ga • Based on ages of terrestrial rocks + age of solar system + models of solar system formation The nebular theory explains the origin of the solar system • Interstellar cloud inherits elements from previous generations of stars o Interstellar cloud of gas and dust o Rotation, gravitational collapse o Solar nebula o Nuclear fusion in the Sun o Condensation o Accretion o Differentiation The solar nebula: • Nuclear fission begins the sun is born • High pressure in center • Low pressure sides Solar System: • Jovian – outer planets o Huge o Gaseous and icy • Terrestial – inner planets o Small o Rocky and metallic SLIDES –Lecture 2 (just for solar system) GEOLOGICALSYSTEMS: Earth consists of layers: • Core: it is the planet’s center is a dense core consisting mostly iron, solid in the inner core and molten in the outer core o The Core: made of Fe-Ni metal o Inner core: Solid o Outer core: Liquid • Mantle: the core is surrounded by this thick layer of rock (dense rock and solid but not dense as the core o Aportion of upper mantle is called the asthenosphere – contains softer rock which is close to melting temperature (weak zone) o The harder rock above the asthenosphere is lithosphere  Lithosphere includes the uppermost mantle and the crust, the thin, brittle, low density layer of rock that covers Earth’s surface  Crust + top of Mantle = Lithosphere • The Crust: o Oceanic crust  Basalt  Dense, thin o Continental crust  Granite  Less dense, thick Plate tectonics: movement of lithospheric plates • Intense heat from inside rises from core to mantle to crust • Where crust is particularly thin or heat flow is high – can harness geothermal energy by drilling boreholes into crust • The heat from the inner layers drives - Mantle convection drives plate motion o Pushing the mantle rock upward (as it warms) and downward (as it cools) o As the mantle material moves, it drags larger plate of brittle lithosphere along its surface o Basically: o Hot rock (low density) rises from depth and cool rock (high density) sinks from the surface o Hot, mobile mantle + thin, cool, brittle lithosphere! → breaks into plates • Plate tectonics and the rock cycle provide the physical foundation for environmental processes: o Intersection of internal and external processes o Internal processes directly influence:  Composition of the atmosphere  Topography and landscape  Climate, weather, soil, biomes  Distribution of mineral, energy resources  Natural hazards (earthquakes, tsunamis,  volcanic eruptions, landslides, etc.) There are several different tectonic environments • Intraplate -“Middle” of the plate o Geologically quiet with some exceptions o “Hot spots” e.g., Hawaii, Gálapagos • Plate Boundaries There are three main types of boundaries: 1. Divergent plate boundaries • Tectonic plates move part from each other or diverge • Magma – rock heated to a molten, liquid state • Magma rises upward to the surface, forming a new crust as it cools and solidifies • New crust is generated • Oceanic (ex: mid-Atlantic ridge) • Continental (ex: EastAfrican Rift) 2. Convergent plate boundaries • Two plates come together or converge • When oceanic crust is involved in a convergent plate boundary a process called subduction occurs – the dense oceanic plate descends into the mantle • Subducted plate is heated and pressurized as it sinks • Water vapours escapes from the subducting plate – helping to melt the overlying rock by lowering its melting tem
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