Science - Astronomy, + Chemistry

Stars

• Stars are massive gas collections, held together by gravity.
• They emit vast energy and are incredibly hot.
• Luminosity: A measure of a star's apparent brightness. Sirius is 22 times brighter than our Sun.
• Color: Indicates temperature.
  • Blue: Hottest
  • White: Hot
  • Yellow: Medium
  • Orange: Cool
  • Red: Coolest
• Life Cycle: Determined by mass.
  • Birth: Starts as nebulas, clouds of gas and dust. Nuclear fusion (hydrogen to helium) creates a protostar.
  • Main Sequence: Most of a star's life, undergoing nuclear fusion.
    • Average Stars: Become red giants in old age.
    • Massive Stars: Become red supergiants in old age.
  • Death:
    • Average Stars: Become white dwarfs, remnants of their cores.
    • Massive Stars: Explode as supernovae, leaving neutron stars or black holes.
      • Neutron Stars: Dense, collapsed cores.
      • Black Holes: Extremely dense with immense gravity.
• Hertzsprung-Russell Diagram: A graph plotting luminosity and temperature, helping understand star life cycles.

Big Bang Theory

• The prevailing cosmological model for the universe's origin and evolution.
• Began as an incredibly hot, dense state and expanded since.
• Evidence:
  • Cosmic Background Radiation: A faint echo of the Big Bang, detected in 1965.
  • Red Shift: Light from distant galaxies shifted to the red end of the spectrum, indicating their movement away from us.
  • Spectral Lines: Analyzing star and galaxy light reveals composition and motion.

Celestial Objects

• Moon: Natural object orbiting a planet, with no atmosphere, responsible for Earth tides.
• Satellites: Artificial objects orbiting a planet, used for communication, navigation, and research.
• Meteoroids: Chunks of rock or metal pulled towards Earth.
• Meteors: Meteoroids heating up in the atmosphere and glowing (shooting stars).
• Meteorites: Meteoroids reaching Earth's surface.
• Asteroids: Rocky, irregularly shaped objects orbiting the Sun, many found in the asteroid belt (Mars and Jupiter).
• Comets: Chunks of frozen gases, rocks, and dust orbiting the Sun. Comet tails always point away from the Sun. The Oort Cloud is a vast comet region at the solar system's edge.

Solar System

• Sun: The Solar System's center, providing heat and light, composed mainly of hydrogen and helium, with sunspots (cooler, darker areas) and a magnetic field causing auroras.
• Planets: Eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune). Pluto is a dwarf planet.
• Early Civilizations: Used Sun and Moon observations for calendars and tracking seasons.

Earth's Movement

• Rotation: Earth spinning on its axis (24 hours), causing day and night. Earth's 23.5-degree tilt causes seasons.
• Revolution: Earth orbiting the Sun (365.25 days), held in orbit by solar gravity.
• Tides: Created by the Moon and Sun's gravitational pulls.

Humans in Space

• Microgravity: Reduced gravitational forces, causing weightlessness; affects human physiology:
  • Weaker heart muscles
  • Muscle atrophy
  • Reduced red blood cell production
  • Weakened immune system
• Solutions: Special diets, exercise, medication, space suits.
• Historical Milestones:
  • Albert (First Monkey in a Rocket)
  • Albert II (First Monkey in Space)
  • Yuri Gagarin (First Human in Space)
  • Neil Armstrong and Buzz Aldrin (First Moon Landing)
  • Columbia Space Shuttle (Maiden Flight)
• Space Shuttle Program: Designed for 100 launches or 10 years. Six shuttles (Enterprise, Columbia, Challenger, Discovery, Atlantis, Endeavour).
• Other Issues: Lack of gravity, lack of resources (food, water, oxygen), psychological effects (depression, anxiety, insomnia).

Constellations

• Groups of stars forming imaginary shapes in the night sky.
• Named after mythological figures, animals, or objects.
• Useful for navigation and tracking seasons.

Chemistry (Properties of Matter)

• Matter: Anything with mass and volume.
• Properties: Characteristics identifying objects (
  • Physical: Observed/measured without changing composition (color, texture, odor, state, hardness, melting point, boiling point, solubility, density, etc.)
  • Chemical: Describes how a substance reacts with others (combustibility, reaction with water/acid, etc.)
• Physical Change: Alters form/appearance but not composition (melting, freezing, evaporation).
• Chemical Change: Forms new substances with different properties (burning, rusting).
• Pure Substance: Cannot be broken into simpler matter (elements, compounds).
• Mixture: Physical combination of substances;
  • Homogeneous: Uniform composition (e.g., salt water);
  • Heterogeneous: Non-uniform composition (e.g., sand and water).

Density

• Relationship between mass and volume.
• Units: Solids (g/cm³), Liquids (g/mL).
• Formula: Density = Mass/Volume

Atomic Theory

• Atom: Smallest, indivisible particle of an element, defining its properties.
• Theories/Discoveries:
  • Dalton (1800): Billiard Ball Model (Identical properties for one element's atoms; different for different elements; atoms combine to new substances.)
  • Thomson (1900): Plum Pudding Model (Atoms with no charge contain positive charges)
  • Rutherford (1900): Nuclear Model (Positive nucleus with most of mass; electrons surrounding it)
  • Bohr (1913): Orbit Model (Electrons in specific energy levels, 2, 8, 8 max electrons in shells. Electrons can change levels by gaining/losing energy.)
  • Chadwick (1932): Nucleus with neutrons and protons.
  • Quantum Mechanical Model: Electrons exist in energy levels around the nucleus in a cloud, precise location uncertain.

Counting Subatomic Particles

• Atomic Number: Number of protons.
• Atomic Mass: Number of protons + neutrons.
• Number of Neutrons: Atomic Mass - Atomic Number.

Elements on the Periodic Table

• Periods: Horizontal rows.
• Groups: Vertical columns.
• Group Number: Indicates valence electrons.

Metals

• Alkali Metals (Group 1): Shiny, soft, low density, most reactive, not found alone in nature.
• Alkaline Earth Metals (Group 2): Shiny, silvery, less soft than alkali metals, reactive, but less so.
• Transition Metals (Groups 3-12): Harder, used "as metal," least reactive.

Metalloids

• Properties of both metals and nonmetals.
• Solid at room temperature. Some are shiny; many are conductors.

Nonmetals

• Halogens (Group 17): Found in different states (solid, liquid, gas); most reactive nonmetals, rarely found alone, poisonous in large quantities.
• Noble Gases (Group 18): Stable, nonreactive, colorless, glow brightly when energized.
• Hydrogen: Its own family, very reactive, non-toxic.

Lewis Dot Diagrams

• Simplified representations of valence electrons. (Symbol with surrounding dots.)
• Shows Valence electrons.

Bohr-Rutherford Diagrams

Show proton, neutron, and electron arrangements in an atom—Nucleus with protons/neutrons, electron shells (with electrons).

Physics (Electricity)

• Static Electricity: Charge buildup on an object.
  • Causes: Friction, contact/conduction, induction.
  • Electrostatic Series: Ranked materials by electron gain/loss tendency.
  • Grounding: Connecting to Earth to remove excess charge.
  • Discharge: Removing excess charge to neutrality.
• Current Electricity: Continuous electron flow.
  • Conductors: Allow free electron movement (e.g., metals).
  • Insulators: Restrict electron movement (e.g., rubber).
• Law of Electric Charges: Like charges repel; unlike charges attract.