Earth Science 8th Grade Midterm Review
Observation: Anything that can be directly noticed by using your senses or instruments that extend your senses
Inference: An interpretation or conclusion based on observations
Classification: Grouping of similar things to make the study of them easier
Mass: The amount of matter making up an object or substance
Volume: The amount of space something takes up (how big)
Volume is found using the formula V=L x W x H
Density: The measure of mass per unit volume, calculated using the formula Density = Mass/Volume.
Volume can also be found using a graduated cylinder
Density: the concentration of matter within an object or substance
Density is measured in grams/cubic centimeters
As temperature increases, density decreases due to the expansion of the molecules
As pressure increases, density increases due to the compression of the molecules
No physical change has any effect on the density, only chemical changes
In most substances, the solid phase is the most dense, liquid is second, and gas is least dense
Water is most dense when in liquid form
Percent error formula: Difference between experimental value and accepted value divided by the accepted value, then multiplied by 100
The shape of the Earth is an oblate spheroid due to its rotation, which causes the equator to bulge and the poles to flatten, affecting the distribution of density in its various phases.
The Earth looks like a perfect circle from space, but is not a perfect circle
The diameter of the equator (equatorial diameter) is slightly larger than the diameter of the poles (the polar diameter)
A person would weigh more at the poles than the equator
Earth’s shape can be determined from pictures of the Earth from space, as well as ships sailing over the horizon and lunar eclipses
The Earth’s crust, atmosphere, and ocean depth is very tiny compared to the size of the Earth
When asked to identify a picture of the Earth, chose the one that looks most like a perfect circle
Latitude: Number of degrees north or south of the equator
Longitude: Number of degrees east or west of the Prime Meridian
Latitude measures north to south
Longitude measures east to west
Polaris (the North Star): The altitude of Polaris represents your latitude north of the equator
The altitude of Polaris can only be measured in the Northern Hemisphere
Field: Any region in space that has some measurable value at every point
Isolines: Lines that connect equal points in value
Contour lines: Isolines that connect points of equal elevation
Gradient: Equals change in field value divided by the distance
Heat Source: An object with the highest heat in the room
Heat Sink: the object with the lowest heat in the room
Contour Interval: Change in elevation between contour lines
Gradient: The change in slope
There is a steep slope if the isolines are close together
A map scale measures distance
Always start at 0 with a map scale
Streams always flow downhill (from high to low elevation)
Contour lines form a V when crossing streams
The stream on a contour map will flow out of the open end of the V
The closed end of the V that contour lines make when crossing a stream represents the upstream part of the river
Water always flows to the lowest places
Rotation: The turning of the Earth on its axis every 23 hours and 56 minutes
Earth rotates 15 degrees per hour
Time zones are 15 degrees apart (longitude)
The time gets later the farther east a person travels
The rotation of the Earth causes all celestial objects in space to appear to revolve around the Earth
Evidence of the Earth’s rotations are the Foucault Pendulum, the Coriolis Effect, and Star Trails
Everything in astronomy goes counterclockwise
The Earth revolves around the sun once every 365.25 days
The Earth moves about 1 degree per day in its revolution
The shape of the Earth’s orbit is slightly elliptical
The sun is one of the foci points in the Earth’s revolution
The Earth is closest to the sun in the winter
The Earth is farthest from the sun in the summer
Perihelion is when the Earth is closest to the sun
Aphelion is when the Earth is farthest from the sun
The evidence that the Earth revolves around the sun is proven since visible constellations and stars change throughout the year as we revolve
The higher (direct) the angle of the sun, the hotter the temperature
As the heat increases, so does the concentration of the heat energy
Earth’s axis is tilted 23.5 degrees
Parallelism: Earth’s axis is always pointed in the same direction in space as it orbits around the sun
The Earth’s axis is always pointed towards Polaris
The north pole is tilted towards the sun on June 21
On June 21, a direct ray of sunlight is on the Tropic of Cancer (23.5 degrees north)
Summer for the Northern Hemisphere is in June
On June 21, the sun is at its highest altitude, giving off the strongest sunlight
There is a longer duration of insolation for the Northern Hemisphere in the summer
June 21 is the day of maximum insolation
The sun rises in the east and sets in the west
In the summer, the sun rises in the northeast and sets in the northwest
In the winter, the sun rises in the southeast and sets in the southwest
In the winter, the north pole is pointed away from the sun
In the winter, a direct ray of sunlight goes to the Tropic of Capricorn (23.5 degrees south)
For the northern hemisphere, the lowest angle of insolation takes place in the winter, giving the weakest sunlight
The lowest duration of insolation takes place in the winter for the Northern Hemisphere
The Vernal equinox is on March 21
The Autumnal Equinox is on September 21
The Summer Solstice is on June 21
The Winter Solstice is on December 21
During the equinoxes, the direct rays from the sun fall on the Equator
The Equator is located at 0 degrees latitude
The entire world has 12 hours of day and 12 hours of night on the Equinoxes
During the equinoxes, the sun rises directly east and sets directly west
The noon sun is always directly south in New York, causing south facing slopes to receive most insolation
The Sun is never directly overhead in New York
High noon is when the sun is at its highest position in the sky for the day
High noon is the same as noon
Shadows point in the opposite direction from the sun
Shadows are long when the angle of the sun is low, and short when the angle of the sun is high
Shadows are long in the morning and evening
Shadows are short at noon
From sunrise to sunset, the length of a shadow will decrease until noon, and then increase
The north pole has 24 hours of darkness in December, and 24 hours of daylight in June
The south pole has 24 hours of daylight in December, and 24 hours of darkness in June
The warmest temperatures occur about 4-6 weeks after June 21
Seasons are not caused by the Earth’s distance from the sun
Radiative Balance: When the amount going in is equal to the amount going out
The temperature of something will remain constant if the object is in radiative balance
The moon revolves around the Earth once every 27.3 days
The phases of the moon take place over a 29.3 day cycle
The phases of the moon are caused by it’s revolution around the Earth
The moon’s revolution around the Earth is slightly elliptical
When an object is in Perihelion, it will have a larger apparent diameter
The Moon is the main cause of the tides on Earth
The tides are caused by the Moon’s gravitational pull on Earth
Kepler’s first law is that all planets revolve in elliptical orbits with the star of their solar system as one of the foci points
The formula for eccentricity is distance between the foci over length of major axis
The eccentricity of a circle is zero
If the eccentricity of something is zero, the foci points will be located on top of each other
Kepler’s second law is that a line from a planet to the sun sweeps over equal areas of space in equal periods of time
Kepler’s second law proves that a planet moves faster when closer to the sun, and slower when farther from it’s sun
Kepler’s third law is that the farther away a planet is from it’s foci points, the longer it’s period of revolution will be
Gravity: The force of attraction between two objects
As mass increases, gravity increases
As distance increases, gravity decreases
If a planet is closer to the sun, the Sun’s gravitational pull on it will increase, causing the planet to move faster
The Bing Bang Theory: Scientists believe that the universe began with all matter and energy concentrated in one small area. When this area exploded, the universe was formed
The elements of the universe were made by the explosion of the atoms in the Big Bang
The universe has been constantly expanding outwards ever since the Big Bang
Galaxies: A collection of billions of stars held together by gravity
Stars: A huge ball of gases that undergoes nuclear fusion to produce vast quantities of energy. This energy is released as electromagnetic energy
Electromagnetic energy is the light that makes stars glow
Luminosity: The brightness of a star compared to the brightness of our sun if both our sun and the star were of equal distance away from us
Solar System: All the objects in space that orbit around one singular sun or star
Planets: Large objects that orbit around the sun
Terrestrial planets: Small, solid, highly dense, and rocky planets that have few moons and no rings
Earth, Mars, Venus, and Mercury are all terrestrial planets
Jovian planets: Large, gassy, low dense planets that have many moons and rings
Jupiter, Saturn, Uranus, and Neptune are all Jovian planets
Asteroids: Thousands of small rocky/metallic objects that orbit around the sun
The Asteroid Belt: A large clump of asteroids located between Jupiter and Mars
Moons: Objects that orbit a planet or asteroid
Comets: Small masses of ice and dust orbiting the sun in very elliptical orbits
The sun’s heat will vaporize the ice on a comet, causing a large tail of gases and dust to stream out into space away from the sun
Meteoroids: Very tiny pieces of rock or metal that orbit the sun
Most meteoroids will break when entering the Earth’s atmosphere, leaving a streak across the sky (this is what makes a shooting star)
A meteoroid that is large enough to not break when entering the Earth’s atmosphere will create an impact crater where it lands
Electromagnetic energy travels in transverse waves and is measured by it’s wavelength
Electromagnetic energy is absorbed best by dark, dull, rough surfaces
Electromagnetic energy is reflected best by light, smooth, and shing surfaces
Any good absorber of energy is a good radiator of energy
Solar energy contains a wide range of wavelengths
Most energy is in the form of visible light
Solar electromagnetic energy is the same as solar energy
Energy is always transferred from regions of high temperatures to regions of low temperatures
Conduction: Energy is passed from molecule to molecule through direct contact
Conduction energy transfers work best with solids
Convection: Energy is transferred within liquids and gases by moving currents due to changes in density
Convection energy transfers are usually liquids and gases
Radiation: The direct transfer of energy in straight lines through space without any medium to transfer the energy
Radiation energy transfers are most commonly associated with the sun and lightbulbs
Earth’s main source of energy is the sun
All objects above absolute zero radiate energy
Absolute zero is 0 degrees kelvin
The hotter an object, the more energy it radiates
When energy is absorbed and then radiated, the radiated energy will always have a longer wavelength
Calorie: The amount of heat needed to raise the temperature of 1 gram of liquid water by 1 degree Celsius
Specific Heat: The amount of heat needed to raise the temperature of 1 gram of any substance by 1 degree Celsius
The higher the specific heat of an object, the more energy it takes to raise the temperature of that substance
Liquid water has the highest specific heat of all natural substances
Liquid water heats up and cools down the slowest
No temperature changes will occur during a change in it’s state of matter
Insolation: Incoming solar radiation
The main form of insolation is visible light, which passes through the atmosphere and is reflected by the clouds
Ultraviolet energy is absorbed by the ozone layer
Infrared energy is absorbed by water vapor and carbon dioxide
Greenhouse Effect: Shortwave visible light passes through the atmosphere and is absorbed by the ground and changed into longwave heat energy, or infrared energy. The infrared energy is reradiated by the ground and absorbed by the carbon dioxide and water vapor in the atmosphere. This causes the heat to build up in the lower atmosphere near the Earth’s surface
Cloudy nights will be warmer than clear nights since water vapor absorbs heat and prevents it from escaping
Global warming is occurring as humans add more carbon dioxide to the atmosphere due to the burning of hydrocarbon fuels.
Global warming causes the melting of the polar ice caps and a rise in the sea level
Land heats faster than water since water has a higher specific heat
Land absorbs energy well since it is dark, dull, and rough
Lang absorbs in only upper layer where water distributes energy all around
Coastal areas have milder temperatures due to effect of ocean water staying cooler in summer and warmer in the winter
An instrument extends your senses
An interface is a boundary across which energy is exchanged
A direct relationship is when the x-variable moves at the same rate as the y-variable
An indirect relationship is when the x-variable increases and the y-variable decreases
A static relationship is when the x-variable increases, but the y-variable stays the same
Most environmental changes are cyclic
The higher the density, the more closely packed the molecules
The formula for density is mass divided by volume
Water molecules expand when it freezes, making it different then other substances
Anything with a density above 1 will sink
Anything with a density below 1 will float
There are three spheres on Earth
Lithosphere: Solid rock
Hydrosphere: Water
Atmosphere: Gases
Polaris will be located on the bottom of the handle for the Little Dipper
180 degrees longitude is known as the International Date Line
Contour Interval: The amount that each contour line will increase by
The closer the isolines, the steeper the slope/gradient
The highest possible elevation for an area on a contour line will be one less then the value of the next contour line
The lowest possible elevation is one greater than the value of the contour line below it
Profile: The side view of a map
Hachured Lines on a contour map indicate a depression
Each Hachured line will decrease in value with the contour interval
The Big Bang was 13.7 billion years ago
Cosmic microwave background radiation is a form of evidence for the Big Bang
The red shift of light from distant galaxies prove that galaxies are moving away and the universe is expanding. This also proves that the Big Bang existed
Our solar system is located on one of the outer arms of the spiral Milky Way Galaxy
All stars produce light energy by nuclear fusion of hydrogen
All stars have life cycles
Stars are classified by their size/luminosity and their temperature/color
Our sun is average sized and average temperature (a main sequence star)
Our solar system formed 4.6 billion years ago when a cloud of gas and dust was pulled together due to gravity
Venus is the hottest planet in our solar system due to the fact that it’s atmosphere is 95% carbon dioxide
The runaway greenhouse effect on Venus allows light to pass through, but traps heat near the surface
Moon phases are cyclic and predictable
The Moon’s period of rotation is equal to the Moon’s period of revolution around Earth
The tides are cyclic and predictable
The tides are caused by the gravitational pull of the Sun and Moon
The Moon has more influence on the tides than the sun because the moon is closer to the Earth
It takes 12 hours and 26 minutes to go from high tide to low tide
Spring Tide: Extreme change from high tide to low tide. Occurs during a new moon and full moon
Neap Tide: Minimal change from high tide to low tide. Occurs when the moon is in the first quarter or third quarter phase
Solar eclipse: The sun is blocked by the moon
Lunar eclipse: The moon is blocked by the sun
A lunar eclipse can only happen during a full moon
A solar eclipse is rare because it is difficult for the sun, Earth, and moon to all be within a straight line of each other since they are on different planes of orbit
Earth’s rotation is a daily event
Earth’s revolution is a yearly event
All celestial objects appear to rise in the east and set in the west
Coriolis Effect: Winds deflect objects to the right in the Northern Hemisphere
Seasons prove that the Earth revolves around the sun
Seasonal changes are caused by Earth’s revolution around the sun and the tilt of the Earth’s axis
Seasons in the Southern Hemisphere are at opposite times than in the Northern Hemisphere
Duration of Insolation: Length of daylight period
The Equator always has 12 hours of daylight
Angle of Insolation: How high the sun is in the sky
The greater the angle of insolation, the greater the intensity of insolation and the warmer the temperature
Vertical rays: Locations that receive sunlight directly overhead (90 degrees)
New York State will never receive vertical rays of sunlight
Solar Time: The time of day that can be estimated by the sun’s location on its path through the sky
Solar noon: When the sun is halfway through the daylight period
Sunrise: When the sun first appears
Sunset: When the sun intersects with the western horizon
Shadows always point in the opposite direction of the light that creates them
Atmospheric Transparency: Clearness of the atmosphere
The atmospheric transparency will decrease if there are clouds, dust, volcanic eruptions, and forest fires
The atmospheric transparency will increase after precipitation occurs
Greenhouse gases: Carbon dioxide, water vapor, and methane
All greenhouse gases allow visible light to pass through the atmosphere, but trap infrared heat that tries to escape
Earth’s atmosphere blocks harmful radiation
The ozone layer blocks ultraviolet radiation
Ultraviolet radiation can cause skin cancer