6th Grade Science Final Exam Notes

6th Grade Science Final Study Guide

The Science Final will be on June 2 and cover Topics 8, 11, and 12. Students are allowed two notecards. It's recommended to review Lesson Checks, Reviews and Assesses, and previous tests, in addition to these notes.

Topic 8

Lesson 1

  • Definitions:

    • Relative Age: The age of a rock or fossil described in relation to other rocks or fossils.
    • Absolute Age: The numeric age of a layer of rocks or fossils. Absolute age can be determined using radiometric dating.
    • Law of Superposition: States that in undisturbed sedimentary rock layers, the oldest layers are at the bottom, and the youngest layers are at the top.
    • Fossil: The preserved remains or traces of an ancient organism.
    • Unconformity: A gap in the geologic record caused by erosion or periods of non-deposition.
    • Radioactive Decay: The process by which an unstable atomic nucleus loses energy by emitting radiation.
    • Radioactive Dating: Determining the age of a rock or fossil by measuring the amount of radioactive isotopes and their decay products.

  • Determining the Age of a Fault:

    • Geologists use the principle of cross-cutting relationships. A fault is younger than the youngest rock layer it cuts through.

  • Index Fossils:

    • Index fossils are fossils of widely distributed organisms that lived during a relatively short period. They are used to help determine the age of rock layers.

  • Unconformity and Overturned Folding:

    • Unconformities represent missing time in the geologic record, making it difficult to determine the continuous sequence of events.
    • Overturned folding can reverse the order of rock layers, making it difficult to apply the law of superposition.

  • Radioactive Decay and Half-Life:

    • If a radioactive element has a half-life of 1,000 years:
      • After 1,000 years, 50% of the radioactive element remains.
      • After 2,000 years, 25% of the radioactive element remains.
      • After 3,000 years, 12.5% of the radioactive element remains.
    • Remaining=Initial:Amount∗(1/2)time/half−lifeRemaining = Initial : Amount * (1/2)^{time/half-life}

  • Using Radioactive Decay:

    • By measuring the ratio of the original radioactive element to its decay product, geologists can estimate how many half-lives have passed, thus estimating the age of the rock or fossil.

Lesson 2

  • Definitions:

    • Geologic Time Scale: A record of Earth's history divided into eons, eras, periods, and epochs.
    • Era: A major division of the geologic time scale, longer than a period.
    • Period: A subdivision of an era on the geologic time scale.

  • Determining Era and Period Boundaries:

    • Scientists use significant events, such as mass extinctions or major changes in the types of organisms present, to define when eras and periods begin and end.

  • Key Timeframes:

    • Precambrian Time: The earliest part of Earth's history, before the Cambrian period. Characterized by the formation of Earth and the early evolution of life.
    • Paleozoic Era: Characterized by the diversification of marine invertebrates, the evolution of fish, and the colonization of land by plants and animals.
    • Mesozoic Era: The age of reptiles, including dinosaurs. Marked by the breakup of Pangaea.
    • Cenozoic Era: The age of mammals. Characterized by the diversification of mammals and the evolution of humans.

Lesson 3

  • Definitions:

    • Invertebrate: An animal without a backbone.
    • Vertebrate: An animal with a backbone.
    • Amphibian: A cold-blooded vertebrate animal that spends part of its life in water and part on land.
    • Reptile: A cold-blooded vertebrate animal with dry, scaly skin that typically lays eggs.
    • Mass Extinction: A widespread and rapid decrease in the biodiversity on Earth.
    • Mammal: A warm-blooded vertebrate animal with hair or fur. Females secrete milk to feed their young.

  • Cambrian Explosion:

    • An important period in Earth's history because there was a rapid diversification of life, with many new types of organisms appearing.

  • End of the Paleozoic Era:

    • Most likely caused by a mass extinction event due to volcanic activity, climate change, change in sea level, and/or asteroid impact.

  • Mesozoic Era:

    • Dominated by reptiles, particularly dinosaurs.
    • Mammals first appeared during this era.

  • End of the Mesozoic Era:

    • Caused by a large asteroid impact, leading to widespread environmental changes and a mass extinction event.

  • Cenozoic Era:

    • Mammals became the dominant type of animal.

Topic 11

Lesson 1

  • Definitions:

    • Satellite: An object that orbits another object in space.
    • Star: A luminous sphere of plasma held together by its own gravity.
    • Planet: A celestial body that orbits a star, is rounded by its own gravity, and has cleared its orbital path.
    • Meteor: A streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere.
    • Comet: A celestial body composed of ice, dust, and gas that orbits the sun and develops a tail when it approaches the sun.
    • Constellation: A group of stars forming a recognizable pattern.
    • Geocentric Model: A model of the universe with Earth at the center.
    • Heliocentric Model: A model of the universe with the Sun at the center.
    • Ellipse: An oval shape.

  • Constellations and Seasons:

    • We can only see certain constellations depending on the season because as Earth orbits the sun, our view of the stars changes.

  • Geocentric vs. Heliocentric:

    • Geocentric Model: Earth is at the center of the universe.
    • Heliocentric Model: Sun is at the center of the universe.
    • The heliocentric model is correct.

  • Galileo's Discoveries:

    • Phases of Venus: Galileo observed that Venus goes through phases like the moon, which would not be possible if it orbited Earth.
    • Moons of Jupiter: Galileo discovered four objects orbiting Jupiter. This showed that not everything orbits Earth.

Lesson 2

  • Definitions:

    • Axis: An imaginary line about which a body rotates.
    • Rotation: The spinning of Earth on its axis.
    • Revolution: The orbiting of Earth around the Sun.
    • Orbit: The path an object takes as it revolves around another object.
    • Solstice: The two days of the year when the sun reaches its maximum or minimum declination.
    • Equinox: The two days of the year when the sun crosses the celestial equator, providing equal lengths of night and day.
    • Gravity: The force that attracts objects with mass toward each other.
    • Law of Universal Gravitation: States that the force of gravity between two objects is proportional to the product of their masses and inversely proportional to the square of the distance between them. F=G∗(m1∗m2)/r2F = G * (m1 * m2) / r^2 where GG is the gravitational constant, m1m1 and m2m2 are the masses of the two objects, and rr is the distance between their centers.
    • Inertia: The tendency of an object to resist changes in its state of motion.

  • Defining a Day on Earth:

    • A day is defined by the time it takes for Earth to make one complete rotation on its axis with respect to a distant star (sidereal day), which is approximately 23 hours and 56 minutes (not exactly 24 hours).

  • Defining a Year on Earth:

    • A year is defined by the time it takes Earth to make one complete revolution around the Sun, which is approximately 365.25 days (not exactly 365 days).

  • Causes of Seasons on Earth:

    • The tilt of Earth's axis (23.5 degrees) causes the seasons. As Earth orbits the sun, different parts of Earth are tilted towards or away from the sun, resulting in variations in sunlight and temperature.

  • Mass and Gravity:

    • Any object with mass has gravity.

  • Mass vs. Weight:

    • Mass: The amount of matter in an object.
    • Weight: The force of gravity acting on an object's mass. Weight=mass∗gravityWeight = mass * gravity.

  • Distance and Gravity:

    • The force of gravity decreases as the distance between two objects increases.

  • Forces Keeping the Moon in Orbit:

    • Gravity: The Earth's gravity pulls the moon towards it.
    • Inertia: The moon's inertia keeps it moving forward.

Lesson 3

  • Definitions:

    • Phase: The different shapes of the moon as seen from Earth.
    • Eclipse: An event in which one celestial body blocks the light from another.
    • Solar Eclipse: An event in which the moon passes between the sun and Earth, blocking the sun's light.
    • Lunar Eclipse: An event in which Earth passes between the sun and the moon, casting a shadow on the moon.
    • Umbra: The darkest part of a shadow.
    • Penumbra: The lighter part of a shadow surrounding the umbra.
    • Tide: The periodic rise and fall of the ocean's surface.
    • Spring Tide: A tide with the greatest difference between high and low tide, occurring when the sun, Earth, and moon are aligned.
    • Neap Tide: A tide with the least difference between high and low tide, occurring when the sun, Earth, and moon form a right angle.

  • Phases of the Moon:

    • The phases of the moon are caused by the changing relative positions of the moon, Earth, and sun. We see different amounts of the illuminated surface of the moon as it orbits Earth.

  • Moon's Day and Year:

    • A "day" on the moon (the time it takes to rotate once) is about the same as a "year" on the moon (the time it takes to orbit the Earth). This is because the moon is tidally locked with Earth.

  • Why Eclipses Don't Happen Every Month:

    • Solar and lunar eclipses don't happen every month because the moon's orbit is tilted relative to Earth's orbit around the sun. The moon only passes directly between the sun and Earth (solar eclipse) or passes directly behind Earth (lunar eclipse) when it crosses Earth's orbital plane.

  • Lunar vs. Solar Eclipse Visibility:

    • More people experience a lunar eclipse than a solar eclipse because a lunar eclipse is visible from anywhere on Earth where the moon is above the horizon. A solar eclipse is only visible from a small area where the moon's umbra touches Earth.

  • Causes of Ocean Tides:

    • The tides of the ocean are caused by the gravitational pull of the moon and the sun on Earth's oceans.

  • Spring vs. Neap Tides:

    • Spring Tide: Occurs when the sun, Earth, and moon are aligned, resulting in a larger tidal range (higher high tides and lower low tides).
    • Neap Tide: Occurs when the sun, Earth, and moon form a right angle, resulting in a smaller tidal range (less difference between high and low tides).

Topic 12

Lesson 1

  • Definitions:

    • Solar System: The sun and all the objects that orbit it.
    • Astronomical Unit (AU): The average distance between Earth and the sun.
    • Sun: The star at the center of our solar system.
    • Planet: A celestial body that orbits a star, is rounded by its own gravity, and has cleared its orbital path.
    • Moon: A natural satellite that orbits a planet.

  • Astronomical Unit (AU):

    • 1 AU is defined as the "average" distance between Earth and the Sun because Earth's orbit is elliptical, so the distance varies throughout the year.
    • 1:AU≈150:million:kilometers1 : AU \approx 150 : million : kilometers

  • Features of the Sun:

    • Sunspots: Darker, cooler areas on the sun's surface caused by magnetic activity.
    • Prominences: Large, bright loops of gas extending from the sun's surface.
    • Solar Flares: Sudden releases of energy from the sun's surface, often associated with sunspots.

  • Formation of Earth:

    • Scientists believe Earth formed from a cloud of dust and gas (nebula) that collapsed under gravity. The cloud began to spin, and most of the material concentrated in the center to form the sun. The remaining material formed a disk around the sun, where particles collided and clumped together to form planetesimals, which eventually formed the planets.

Lesson 2

  • Definitions:

    • Electromagnetic Radiation: Energy that travels in the form of waves.
    • Visible Light: The portion of the electromagnetic spectrum that is visible to the human eye.
    • Spectrum: The range of electromagnetic radiation.
    • Wavelength: The distance between successive crests of a wave.
    • Telescope: An instrument used to collect electromagnetic radiation from distant objects.

  • Optical Telescopes:

    • Optical telescopes collect visible light.

  • Radio Telescopes:

    • Radio telescopes collect radio waves.

  • Most Important Space Technology:

    • Space-based telescopes are located in space to avoid atmospheric distortion of electromagnetic radiation, particularly at wavelengths other than visible light. They provide clearest view of distant stars.

Lesson 3

  • Definitions:

    • Nebula: A cloud of gas and dust in space.
    • Protostar: A contracting mass of gas and dust that represents an early stage in the formation of a star.
    • White Dwarf: The remnant of a star that has exhausted its nuclear fuel.
    • Supernova: The explosion of a massive star.
    • Apparent Brightness: How bright a star appears from Earth.
    • Absolute Brightness: The actual brightness of a star, regardless of its distance.

  • Lifespan of Our Sun:

    1. Nebula: Our sun began as a nebula, a cloud of gas and dust.
    2. Protostar: Gravity caused the nebula to contract and heat up, forming a protostar.
    3. Main Sequence Star: The protostar became hot enough for nuclear fusion to begin in its core, and it became a main sequence star (like our sun is now).
    4. Red Giant: After about 10 billion years, the sun will run out of hydrogen fuel in its core. The core will contract, and the outer layers will expand and cool, turning the sun into a red giant.
    5. Planetary Nebula: The outer layers of the red giant will drift away, forming a planetary nebula.
    6. White Dwarf: The core of the red giant will collapse into a small, dense white dwarf.
    7. Black Dwarf (Theoretical): Over an extremely long time, the white dwarf will cool and fade, eventually becoming a black dwarf.

  • Neutron Stars, Pulsars, and Black Holes:

    • Neutron Stars: The extremely dense remnant of a massive star that has collapsed.
    • Pulsars: A rapidly rotating neutron star that emits beams of radio waves and other electromagnetic radiation.
    • Black Holes: A region of spacetime with such strong gravity that nothing, not even light, can escape it.

  • Color and Surface Temperature:

    • The color of a star signifies its surface temperature. Hotter stars are blue, while cooler stars are red. Our sun is a yellow star of intermediate temperature.

Lesson 4

  • Definitions:

    • Galaxy: A large collection of stars, gas, and dust held together by gravity.
    • Universe: Everything that exists, including all matter, energy, space, and time.
    • Light-Year: The distance light travels in one year.
    • Big Bang: The event that is thought to have created the universe.

  • Order of Magnitude:

    • Star Systems < Star Clusters < Galaxies

  • Types of Galaxies:

    • Spiral Galaxies: Have a central bulge and spiral arms.
    • Elliptical Galaxies: Have an elliptical shape and are made up of older stars.
    • Irregular Galaxies: Have no defined shape.
    • Lenticular Galaxies: Have a central bulge and a disk but no spiral arms.

  • Expanding Universe:

    • The universe is getting bigger (expanding).

  • Dark Matter:

    • Dark matter is matter that does not interact with light, so it cannot be seen directly. Its presence is inferred from its gravitational effects on visible matter.

  • Dark Energy:

    • Dark energy is a mysterious force that is thought to be causing the expansion of the universe to accelerate.