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Praxis II Middle School Science 5440
Terms in this set (110)
generalization and description of how natural phenomena occur (but not why).
explanation that is supported by a large body of evidence.
something that is directly observable and generally accepted as true.
a testable explanation for an observation of natural phenomena - may involve predictions or inferences.
manipulated variable; controlled by the experimenter; affects the dependent variable.
the measured variable; depends on the independent variable.
independent variable held constant; does not affect the dependent variable; ensures a more clear relationship between independent and dependent variables.
father of physics
distance between celestial bodies
has mass and takes up space
Mass vs. Weight
Mass - how much matter / Weight - matter x gravity
Chemical change (examples)
rusting, fermentation, burning
Physical Properties (examples)
color, smell, density, boiling point, molecular weight
Chemical Properties (examples)
reactivity, pH, flammability
pure substance which cannot be broken down any further chemically; contains only one type of atom. Atoms of an element are chemically identical in all states of matter.
# protons (= #electrons)
protons + neutrons
smallest unit of matter, mostly empty space; contains nucleus (protons and neutrons) and orbiting electrons.
positively charged nucleus, mostly empty space, orbiting electrons
Reactivity depends on...
the configuration of electrons in the outermost orbital (valence electrons); reactivity = tendency to lose or gain electrons.
two or more atoms combine. Expends great amounts of energy (endothermic)
atom splits. Does not occur in nature. Releases great amounts of energy (exothermic)
pure substance composed of two or more different atoms, chemically bonded. A compound contains many, many molecules.
one unit of a compound; water is a compound and one molecule of water consists of two hydrogen atoms and one oxygen atom. Molecules/Compounds react differently than their individual components.
9 elements naturally exist as diatomic molecules (at room temperature)
H2 O2 N2 F2 Cl2 I2 Br2 ("HONF - Cliber")
2 elements - liquid at room temperature
States of matter
solid: definite shape, definite volume.
liquid: indefinite shape, definite volume.
gas: indefinite shape, indefinite volume.
State changes (physical changes)
Solid → Liquid - melting, fusion
Solid → Gas - sublimation (dry ice)
Gas → Solid - deposition
Gas → Liquid - condensation
Liquid → Gas - evaporation, boiling
Liquid → Solid - freezing, solidification
The Law of Conservation (of Mass and Energy)
mass and energy are neither created nor destroyed in a closed system, but rather change form.
Elements in the Earth's atmosphere
Nitrogen (78%), Oxygen (20%), Argon (1%), CO2
Elements in the Earth's crust
Oxygen (46%), Silicon (28%), Aluminum (8%), Iron (5%), Calcium, Sodium, Magnesium, Potassium, Titanium, Hydrogen
Heat vs. temperature
Heat is a measure of total energy (both kinetic and potential) at the molecular level. Heat is expressed in Joules.
Temperature the average kinetic energy of molecules in an object. Temperature is expressed in Kelvin (K), Celsius (C), or Fahrenheit (F).
Fahrenheit → Celsius: (5/9)F-32 = C
Celsius → Fahrenheit: (9/5)C +32 = F
Celsius → Kelvin: C +273 = K
Transfer of energy
conduction (objects in contact)
convection (fluids circulate)
radiation (no medium needed)
1st Law of Thermodynamics
Matter and energy are conserved (energy in = energy out) in a closed system.
2nd Law of Thermodynamics
Entropy always increases in a closed system. Not all energy is transferred; some is "lost" as heat.
3rd Law of Thermodynamics
entropy approaches equilibrium with low temperatures (but absolute zero is not possible).
"Zeroth" Law of Thermodynamics
If systems 1 and 2 are both in equilibrium with 3, then 1 and 2 are also in equilibrium with each other.
The rate of reaction increases with...
increases in temperature, concentration, or surface area.
mixture of 2 or more substances (can be in liquid, gas, or solid form)
Solute vs. solvent
Solvent - greater in quantity/volume
Solute - lesser in quantity/volume
the amount of solute in a solvent (solute : solvent)
the amount of solute needed to saturate a solution.
negative log of the concentration of hydrogen ions
low pH (1-6), high concentration of H+ ions, turns blue litmus paper red
high pH (8-13), low concentration of H+ ions, turns red litmus paper blue
neutral (tap water, human saliva)
resist change in pH value
a naturally occurring, inorganic substance (including native elements) with a defined composition and crystal structure.
an aggregate substance that may be a mixture of several minerals; no definite composition or structure; may contain both organic and inorganic material
Mineral properties (how minerals are classified)
color, hardness, luster, fracture, crystal habit, specific gravity, tenacity (and sometimes fluorescence or radioactivity)
formed from particles of sand, shells, pebbles, and other fragments of material (sediment); sediment accumulates in layers and over a long period of time hardens into rock
examples: limestone, dolomite, sandstone, flint, breccia, shale
formed from molten rock (magma) that cools and hardens; if lava cools very quickly, no crystals form and the rock looks shiny and glasslike (obsidian)
igneous rocks crystallize
Earth's surface and the slow cooling that occurs there allows large crystals to form.
igneous rocks erupt
the Earth's surface where they cool quickly.
modified by heat, pressure and chemical processes, usually while buried deep below Earth's surface; extreme conditions modify the rock's properties.
examples: slate, soapstone, marble
Minerals in the Earth's crust
O, Si, Al, Fe, Ca, Na, K, Mg
Layers of Earth
Inner core → outer core → mantle → crust → lithosphere and hydrosphere → atmosphere (also, biosphere)
Layers of the atmosphere
Tropo → strato → meso → thermo/iono → exo
Highest concentration of ozone
between the troposphere and stratosphere
97% salt water; 3% fresh water (most fresh water is locked up in glaciers)
Folding, faulting, earthquakes and volcanoes occur due to...
the movement of tectonic plates
Folds are created in rock (or plates) when they experience compressional stress; rock is being pushed inward from both sides; happens gradually over time.
anticline fold - forms an arch that looks like an 'A'
syncline fold - the fold sinks downward, looks like a 'V'
monocline fold - rock layers form an S-shape, going in the same (mono-) direction.
Faults are cracks in the earth's crust where movement of tectonic plates occurs on at least one side.
Tensional stress (plates pulled apart) forms a "normal" fault.
Compressional stress (plates pushed together) forms a "reverse" ("thrust up") fault.
Shear stress (plates move past each other in opposite directions) forms a "strike-slip" fault.
Map of tectonic plates
When the force of the moving tectonic plates finally overcomes the friction of the jagged edges of the fault and it unsticks, stored up energy is released. The energy radiates outward from the fault in all directions in the form of seismic waves.
A combination of gases and molten rock called magma lies between the Earth's crust and the mantle. A volcano is like a chimney flue that extends down to a pool of magma. When pressure builds up, eruptions occur. When magma flows out of a volcano, we call it lava. Volcanos are usually found along fault lines.
proposed continental drift (1915)
Supercontinent Pangaea existed 200 million years ago; it slowly broke into subcontinents that began to drift; this is supported by the fossil record. Wegener's hypothesis has been rejected in favor of plate tectonic theory.
Plate Tectonic Theory
The continents rest on massive slabs of rock called tectonic plates. The plates are always moving and interacting in a process called plate tectonics. Most likely began ~3 billion years ago.
Evidence for Plate Tectonic Theory
Fossil record similarities that span multiple continents
The "fit" of the continents
Concentration of geothermal and seismic activity along plate boundaries
Seafloor spreading and ridges
Molten rock (magma) rises from within the Earth and adds new seafloor (oceanic crust) to the edges of the old. Seafloor spreading is most dynamic along giant underwater mountain ranges known as mid-ocean ridges. As the seafloor grows wider, the continents on opposite sides of the ridge move away from each other. The North American and Eurasian tectonic plates, for example, are separated by the Mid-Atlantic Ridge.
The hydrologic cycle - diagram
Agents of erosion
water, wind, ice, waves, gravity
oxidation, hydrolysis and carbonation
rocks breaking apart without changing their chemical composition; may be caused by frost or root wedging, temperature changes, erosion, biological activity, and "unloading"
Runoff v. Infiltration
When precipitation hits the ground, infiltration occurs when surface water enters the soil. When the soil becomes saturated, excess water has to go somewhere - overflow in the form of runoff, which is when surface water flows over land.
Effects of runoff
Runoff may contain excess nutrients like nitrogen and phosphorus, pesticides, pollutants, waste, bacteria and more. Runoff may decrease water quality in watersheds.
Porosity and Permeability
Porosity - how much of a rock is open space.
Permeability - the ease with which a fluid can move through a porous rock.
4.5 billion years old, 3rd planet from sun, circumference 40,000km (25,000 miles), human population 7 billion, distance to sun 93 million miles
Law of Superposition
Older layers (or beds ) of sedimentary rocks are found below younger layers.
How to determine the age of rocks
Two ways - numerical dating and relative dating.
Numerical dating determines the actual ages of rocks through the study of radioactive decay.
Relative dating cannot establish absolute age, but it can establish whether one rock is older or younger than another.
The Principle of Cross-Cutting Relationships
Rock formations that cut across other rocks must be younger than the rocks that they cut across.
any material that is trapped inside a rock or mineral during its formation
The Law of Included Fragments / The Principle of Inclusions
inclusions are older than the host rock
The technique of comparing the abundance ratio of a radioactive isotope to a reference isotope.
Radioactive isotopes decay at predictable rates. The amounts of the radioisotopes present in a sample can provide a measurement of the time elapsed.
Fossils are formed in a number of different ways, but most are formed when a plant or animal dies in a watery environment and is buried in mud and silt. Soft tissues quickly decompose leaving the hard bones or shells behind. Over time sediment builds over the top and hardens into rock. As the encased bones decay, minerals seep in replacing the organic material cell by cell in a process called "petrification." Alternatively the bones may completely decay leaving a cast of the organism. By far the most common fossil remains are those of shelled invertebrates.
Major events in Earth's history (in order)
Earth is formed ~4.5bya
Origin of Life ~3.5bya
First photosynthetic bacteria ~3.4bya
Plate tectonics ~3bya
Oxygen explosion and first "snowball Earth" ~2.4bya
Multicellular life ~1bya
Cambrian explosion ~530mya
Plants colonize land ~460mya
Ordovician-Silurian extinction (85% marine life) ~430mya
Pangaea forms ~3mya
Permian extinction ~250mya
First mammals ~220mya
Triassic extinction ~200mya
Cretaceous-Tertiary (or K-T) extinction ~65mya (wiped out dinosaurs)
Primates evolve ~60mya
Homo sapiens ~200,000 years ago
Oceans and seas - map
Ocean waves are movement of energy through a medium. There are different types of waves such
as Capillary (wind driven), Wind Wave (wind over ocean), Seiche (change in atmospheric pressure, storm surge or tsunami), seismic wave (volcanic eruption of faulting on the seafloor, Tide (gravitational attraction of the rotation of earth).
Tides are caused by inertia and the gravitational pull of both the moon and the sun on the earth's surface. This causes the rhythmic rising and falling of the water on the earth's surface. Most coasts have semidiurnal tides or 2 high and 2 low tides per day. Neap Tides occur are the smallest variations between the high and low tide and occur when the sun earth and moon are at right angles. Spring tides occur when the earth sun and moon are in a straight line and are the largest variations between the high and low tide.
an area where sea floor spreading has created
flat plains like area under water
Ocean floor features
Currents are caused by the sinking of colder dense water and the rising of warmer water. The water circulates due to the uneven heating of the Earth between the poles and the equator.
Ocean currents - map
Bodies of water where rivers meet the sea. They contain "brackish" water (mix of FW and SW). Highly productive ecosystems.
An atoll is a ring-shaped coral reef or island that surrounds a body of water called a lagoon. Atolls develop with underwater volcanoes, called seamounts.
Where is Earth's water?
Properties of water
Hydrogen bonds - allows ice to float on water, allows for high specific heat capacity and high heat of vaporization. Stabilizes temperatures on Earth, acts as a buffer.
Universal solvent - especially for other polar molecules like ionic compounds, minerals, etc.
cohesion, adhesion, capillary action in plants
Specific heat capacity
the amount of heat that must be absorbed or lost for 1 gram of a substance to change its temperature by 1 degree C.
Earth's magnetic field
the geomagnetic field, is the magnetic field that extends from the Earth's interior to where it meets the solar wind, a stream of charged particles emanating from the Sun and deep space. It is tilted at an angle of about 11 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth. Unlike a bar magnet, however, Earth's magnetic field changes over time because it is generated by a geodynamo (in Earth's case, the motion of molten iron alloys in its outer core).
a celestial body (planet or star) with rotating, convecting, and electrically conducting fluids at its core, can maintain a magnetic field.
Geological timescale - we live in the...
Phanerozoic eon, Cenozoic era, Quaternary period, Holocene epoch
Note: 88% of geological time is before the Cambrian period.
Phanerozoic eras in order
Paleozoic, Mesozoic, Cenozoic
At sea level, air density is around 1.2 kg m-3
Air density decreases with altitude
the cumulative effect of the push exerted by each molecular collision on its surroundings
Pressure is a force distributed over an area. The unit of Pressure is N m-2, or Pascal
Relationship between density, pressure and temperature
p = R r T
p is pressure,
r (Greek rho) is density
T is temperature (in degrees Kelvin),
R is the specific gas constant, which varies from gas to gas.
For dry air, R is 287 J K-1 kg-1.
This very important relationship is known as the Equation of State
Equation of State
(1) for constant density, pressure increases with temperature (that is, if the molecules have a higher average kinetic energy, they exert a greater push on their surroundings);
(2) for constant temperature, pressure increases with density (the more molecules per unit volume, the greater the push exerted by collisions);
(3) for constant pressure, temperature and density are inversely related (that is, if there are fewer molecules in a given volume, they need to be traveling at a greater average speed to exert the same pressure).
Note: if we heat a mass of air, we increase its pressure, if the air is allowed to expand to equalise the pressure difference with the surrounding air, the density will decrease. When this happens, it will be lighter than the same volume of surrounding air, and will rise
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