3.3 Physical and Earth Sciences

Section 3.3: Physical and Earth Sciences

Physical science deals with matter and energy, while Earth science covers geology, astronomy, and meteorology.

States of Matter and Phase Changes

Matter is anything that has mass and takes up space. It exists in three primary states:

• Solids: Have a definite shape and volume. Particles are tightly packed and vibrate in place.
• Liquids: Have a definite volume but take the shape of their container. Particles are close but can flow.
• Gases: Have no definite shape or volume. Particles are far apart and move rapidly.

Phase Changes and Thermal Energy

Adding or removing heat energy causes matter to transition between states:

• Melting (Solid -> Liquid) and Vaporization (Liquid -> Gas) absorb heat.
• Freezing (Liquid -> Solid) and Condensation (Gas -> Liquid) release heat.
• Sublimation (Solid -> Gas, e.g., dry ice) absorbs heat; Deposition (Gas -> Solid, e.g., frost forming) releases heat.

Physical vs. Chemical Changes

• Physical Change: Changes the form or appearance of a substance but does not alter its chemical identity (e.g., tearing paper, melting ice, dissolving salt in water).
• Chemical Change: A chemical reaction that produces new substances with distinct properties (e.g., iron rusting, wood burning, paper charring). Indicators of a chemical change include color change, gas production (bubbling), temperature change, and precipitate formation.

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Forces and Motion: Newton's Laws

• Speed: The rate at which an object covers distance (Speed = Distance / Time).
• Velocity: Speed in a specific direction (e.g., 50 km/h East).
• Acceleration: Any change in velocity (speeding up, slowing down, or changing direction).
• Friction: A force that opposes motion between two touching surfaces, generating heat.
• Gravity: An attractive force between masses. Earth's gravity pulls all objects toward its center at 9.8 m/s².

Newton's Three Laws of Motion

1. First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion at a constant velocity unless acted upon by an unbalanced force (e.g., a passenger leaning forward when a car brakes suddenly).
2. Second Law (F=ma): Acceleration is directly proportional to force and inversely proportional to mass (e.g., it requires more force to push a heavy bowling ball than a light tennis ball at the same acceleration).
3. Third Law (Action-Reaction): For every action, there is an equal and opposite reaction (e.g., when a rocket burns fuel downward, the escaping gases push the rocket upward).

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Energy: Heat, Light, Sound, and Electricity

Energy is the ability to do work or cause change.

Heat Transfer

Heat always flows from hotter substances to cooler ones:

• Conduction: Transfer of heat through direct contact (e.g., a metal pan heating up on a hot stove).
• Convection: Transfer of heat through the movement of fluids or gases due to density differences (e.g., warm air rising above a heater, creating a current).
• Radiation: Transfer of heat through electromagnetic waves, requiring no medium (e.g., solar energy warming Earth's surface).

Light Energy

Light is an electromagnetic wave that travels in straight lines. When light hits a boundary, it can be:

• Reflected: Bounces off a surface (e.g., light hitting a mirror).
• Refracted: Bends as it passes from one medium to another of different density, changing its speed (e.g., a straw appearing bent in a glass of water).
• Absorbed: Taken in by the material and converted to thermal energy (e.g., a dark asphalt road absorbing sunlight).

Sound Energy

Sound is a mechanical wave produced by vibrations.

• Medium Required: Sound must travel through a medium (solid, liquid, or gas). It cannot travel in a vacuum.
• Transmission: Sound travels fastest in solids (particles are closest) and slowest in gases.
• Pitch: Determined by the wave's frequency (high frequency = high pitch).
• Volume: Determined by the wave's amplitude (large amplitude = loud volume).

Electricity

• Circuits: A closed loop through which current flows.
  • Series Circuit: A single path. If one bulb breaks, the entire circuit fails and all bulbs go out.
  • Parallel Circuit: Multiple paths. If one path is interrupted, current still flows through the other paths, keeping the other bulbs lit.
• Conductors vs. Insulators: Conductors (like copper and aluminum) allow electrons to flow easily. Insulators (like rubber, wood, and plastic) resist the flow of electrons.

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Earth Systems and Plate Tectonics

Earth has three primary layers:

1. Crust: The thin, rocky outermost layer.
2. Mantle: Hot, semi-solid rock. Convection currents in the mantle drive the movement of tectonic plates.
3. Core: Divided into a liquid outer core and a solid inner core, both composed of iron and nickel.

Tectonic plates meet at boundaries:

• Convergent Boundary: Plates collide, forming mountains (e.g., Himalayas) or subduction zones (volcanic arcs).
• Divergent Boundary: Plates pull apart, creating rift valleys or mid-ocean ridges.
• Transform Boundary: Plates slide past one another, causing friction and earthquakes (e.g., San Andreas Fault).

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Weathering, Erosion, and Deposition

• Weathering: The breakdown of rock into sediment.
  • Mechanical: Physical fracturing (e.g., frost wedging).
  • Chemical: Alteration of rock chemistry (e.g., acid rain dissolving limestone).
• Erosion: The transport of sediment by wind, water, ice, or gravity.
• Deposition: The settling of transported sediment in a new location (e.g., a river delta or sand dune).

Table 3.3.1: Shaping Earth's Surface

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The Rock Cycle

• Igneous: Formed from cooling magma or lava.
• Sedimentary: Formed from compacted and cemented sediments. These rocks contain fossils.
• Metamorphic: Formed when existing rocks are modified by heat and pressure without melting.

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Solar System and Astronomy

• Rotation: Earth spinning on its axis (takes 24 hours, causing day and night).
• Revolution: Earth orbiting the Sun (takes 365.25 days, causing the calendar year).
• Seasons: Caused by the 23.5-degree tilt of Earth's axis. As Earth revolves, different hemispheres receive direct or indirect sunlight.
• Moon Phases: Caused by the changing angles of reflected sunlight visible from Earth as the Moon orbits our planet.
• Eclipses:
  • Solar Eclipse: Moon blocks sunlight from reaching Earth (Sun-Moon-Earth).
  • Lunar Eclipse: Earth blocks sunlight from reaching the Moon (Sun-Earth-Moon).

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Weather and Climate

• Weather: Short-term atmospheric conditions.
• Climate: Long-term average weather patterns.
• Water Cycle: Evaporation/Transpiration -> Condensation (clouds) -> Precipitation -> Runoff.
• High (H) vs. Low (L) Pressure: High pressure brings cool, dry air and clear skies. Low pressure brings warm, moist air and stormy weather.
• Fronts: A cold front occurs when a cold air mass displaces a warm air mass, causing severe storms. A warm front occurs when warm air slides over cold air, bringing light, steady rain.