121 terms

8th grade science, Virginia SOL key concepts, part 1

Potential energy
Potential energy is energy that is not "in use" and available to do work.
Kinetic energy
Kinetic energy is energy that is "in use" — the energy a moving object has due to its motion. For example, moving water and wind have kinetic energy.
Chemical energy
The chemical energy in fossil fuels is potential energy until it is released.
What are fossil fuels?
Solar energy from the ancient past is stored in fossil fuels, such as coal, petroleum, and natural gas. Fossil fuels are rich in the elements carbon and hydrogen. These sources of energy take very long periods of time to form and once depleted, are essentially nonrenewable.
Is nuclear power renewable or non-renewable?
Nuclear power is also a source of nonrenewable energy.
What are renewable energy sources?
Many of Earth's energy resources are available on a perpetual basis. These include solar, wind, water (hydropower, tidal and waves), biofuels and geothermal energy. Some energy sources can be replenished over relatively short periods of time. These include wood and other biomass. All are considered renewable.
Secondary sources of energy
Sources of energy, such as electricity, that are used to store, move, and deliver energy easily in usable form. Hydrogen is also a secondary source of energy, also called an energy carrier.
Conversion of energy
Thermal and radiant energy can be converted into mechanical energy, chemical energy, and electrical energy and back again.
Role of the sun on earth
Earth receives only a very small portion of the sun's energy, yet this energy is responsible for powering the motion of the atmosphere, the oceans, and many processes at Earth's surface.
Solar radiation is made up of what different types of radiation?
infrared, visible light, and ultraviolet.
Greenhouse effect
Incoming solar radiation is in close balance with the energy that leaves the atmosphere; otherwise Earth would heat up or cool down. Excess carbon dioxide and other gases may disrupt this balance, creating a greenhouse effect.
What happens to the sun's incoming energy when it reaches the earth?
About one-third of the sun's incoming energy is reflected back out to space. About one-half of the energy striking Earth is absorbed by Earth's surface.
Is the earth's surface heated equally or unequally?
Earth's surface is heated unequally.
What happens when air or water is heated?
The molecules move faster and farther apart, reducing their density and causing them to rise.
What happens when air or water is cooled?
Cooler air or water molecules move more slowly and are denser than warm air or water.
Warm air or water rising coupled with cooler air or water descending forms a cyclic rising/falling pattern called convection.
What transfers the earth's thermal energy?
Radiation and convection from Earth's surface transfer thermal energy. This energy powers the global circulation of the atmosphere and the oceans on our planet.
How do clouds form?
As bodies of water (oceans, lakes, rivers, etc.) absorb thermal energy, the water evaporates causing the air to be warm and moist. Warm, moist air is less dense than cold, dry air, so it rises relative to colder, drier air. As warm, moist air rises, it gives off some thermal energy as the moisture condenses, forming clouds. Clouds are not gaseous water vapor; rather they are minute, condensed water particles.
How do thunderstorms form?
Some thunderstorms are formed where the land is strongly heated.
How do hurricanes form?
Hurricanes form over warm, tropical water and are fed by the energy of that water.
What are the main components of an atom?
The basic structural components of a typical atom are electrons, protons, and neutrons.
What are the main components of the nucleus?
Protons and neutrons comprise the nucleus of an atom.
An element is a form of matter made up of one type of atom. The atoms of an element are basically alike, though the number of neutrons may vary.
How do elements differ?
The atoms of one element differ from those of another element in the number of protons.
Elements can be represented by
chemical symbols.
Two or more atoms of different elements may combine to form a compound.
Chemical symbols
Each different element in the compound is represented by its unique symbol. The number of each type of element in the compound (other than 1) is represented by a small number (the subscript) to the right of the element symbol.
Chemical equations
can be used to model chemical changes, illustrating how elements become rearranged in a chemical reaction.
What elements form the largest portions of the earth's matter?
A limited number of elements, including silicon, aluminum, iron, sodium, calcium, potassium, magnesium, hydrogen, oxygen, nitrogen, and carbon, form the largest portion of Earth's crust, living matter, the oceans, and the atmosphere.
Why do water molecules "stick together"?
Among water's unique properties is that one side of each water molecule is slightly negative and the other is slightly positive. Individual water molecules, therefore, attract other water molecules like little magnets as the slightly positive portion of a water molecule is attracted to the slightly negative portion of an adjacent water molecule. In this way, water molecules "stick together."
Why is water called the universal solvent?
Due to water's polar nature, a large number of substances will "dissolve" in water. For this reason, water is often called the universal solvent.
Unique properties of water
Water is the only compound that commonly exists in all three states (solid, liquid, gas) on Earth. The unique properties of water are a major factor in the ability of our planet to sustain life. Additional properties of water are its high surface tension and the large range of temperature (0-100 degrees Celsius) in which it can be found in the liquid state, as well as the fact that, unlike other substances, solid water is less dense than liquid water.
How do large bodies of water make the climate more mild?
Water is able to absorb thermal energy without showing relatively large changes in temperature. Large bodies of water act to moderate the climate of surrounding areas by absorbing thermal energy in summer and slowly releasing that energy in the winter. For this reason, the climate near large bodies of water is slightly milder than areas without large bodies of water.
How has water shaped our environment?
Water (rain, ice, snow) has shaped our environment by physically and chemically weathering rock and soil and transporting sediments. Freezing water can break rock without any change in the minerals that form the rock (physical weathering). This usually produces small particles and sand. Water with dissolved gases and other chemicals causes the minerals in rocks to be changed, leading to the deterioration of the rock (chemical weathering).
Proportion of salt water to fresh water on earth?
Most of Earth's water is salt water in the oceans (97 percent). Nonfrozen, fresh water makes up less than 1 percent of the water on Earth.
Why is water essential for agriculture.
Crops watered by reliable irrigation systems are more productive and harvests more dependable.
Why is water is an important resource used in power generation.
Hydroelectric power plants make use of the kinetic energy of water as it flows through turbines. Water is also heated in power plants and turned to steam. The steam is used to turn turbines, which generate electricity.
Role of water in disposing of human waste
In the past, streams and rivers were often used to dispose of human waste, and open sewers were common. During the mid-1800s, public health officials recognized the connection between disease outbreaks and contamination of public wells and drinking water. Advances in water treatment and sanitary sewers have helped eliminate diseases associated with human waste.
Why is it important to conserve water resources?
Due to water's importance in power generation, agriculture, and human health, it is important to conserve water resources.
What is air?
Air is a mixture of gaseous elements and compounds. These include nitrogen, oxygen, water, argon and carbon dioxide. Nitrogen makes up the largest proportion of air.
Relationship between altitude and air pressure
Air pressure decreases as altitude increases. Temperature decreases as altitude increases in the lowest layer of the atmosphere.
Moisture in the air is called humidity.
What are the layers of the atmosphere?
The atmosphere is made up of layers (troposphere, stratosphere, mesosphere, and thermosphere) that have distinct characteristics.
Where is most of the air found?
Most of the air that makes up the atmosphere is found in the troposphere (the lowest layer). Virtually all weather takes place there.
What affects the earth's atmosphere?
Forest fires and volcanic eruptions are two natural processes that affect Earth's atmosphere. Many gaseous compounds and particles are released into the atmosphere by human activity. All of the effects of these materials are not yet fully understood.
What determines weather conditions?
The amounts of thermal energy and water vapor in the air and the pressure of the air largely determine what the weather conditions are.
Where are clouds found?
Clouds are important indicators of atmospheric conditions. Clouds are found at various levels within the troposphere.
Three major types of clouds are
cumulus, stratus, and cirrus.
A form of oxygen, can form near the surface when exhaust pollutants react with sunlight. This pollutant can cause health problems. Naturally occurring ozone is also found in the upper atmosphere and helps to shield Earth from ultraviolet radiation.
Maintaining good air quality is a crucial goal for modern society
It is everyone's responsibility to work toward it.
What do weather maps show?
Weather maps show much useful information about descriptive air measurements, observations, and boundaries between air masses (fronts). The curved lines showing areas of equal air pressure and temperature are key features of weather maps. Weather maps are important for understanding and predicting the weather.
An ecosystem is made up of...
the biotic (living) community and the abiotic (nonliving) factors that affect it. The health of an ecosystem is directly related to water quality.
Abiotic factors
determine ecosystem type and its distribution of plants and animals as well as the usage of land by people. Abiotic factors include water supply, topography, landforms, geology, soils, sunlight, and air quality/O2 availability.
How can human activities alter abiotic components and thus accelerate or decelerate natural processes.
For example, people can affect the rate of natural erosion. Plowing cropland can cause greater erosion, while planting trees can prevent it. Flood protection/wetland loss is another example.
A watershed
The land that water flows across or through on its way to a stream, lake, wetland, or other body of water. Areas of higher elevations, such as ridgelines and divides, separate watersheds.
Where do the three major regional watershed systems in Virginia lead to?
The Chesapeake Bay, the North Carolina sounds, or the Gulf of Mexico.
River systems
They are are made up of tributaries of smaller streams that join along their courses. Rivers and streams generally have wide, flat, border areas, called flood plains, onto which water spills out at times of high flow.
Rivers and streams carry and deposit sediment.
As water flow decreases in speed, the size of the sediment it carries decreases.
they form the transition zone between dry land and bodies of water such as rivers, lakes, or bays.
What is the function of wetlands?
Both tidal and nontidal wetlands perform important water quality functions, including regulating runoff by storing flood waters; reducing erosion by slowing down run-off; maintaining water quality by filtering sediments, trapping nutrients, and breaking down pollutants; and recharging groundwater. They also provide food and shelter for wildlife and fish and nesting and resting areas for migratory birds.
What is the function of Estuaries?
Estuaries perform important functions, such as providing habitat for many organisms and serving as nurseries for their young.
The Chesapeake Bay
An estuary where fresh and salt water meet and are mixed by tides. It is the largest estuary in the contiguous United States and one of the most productive.
Water quality monitoring
the collection of water samples to analyze chemical and/or biological parameters. Simple parameters include pH, temperature, salinity, dissolved oxygen, turbidity, and the presence of macroinvertebrate organisms.
The solar system consists of...
the sun, moon, Earth, other planets and their moons, meteors, asteroids, and comets. Each body has its own characteristics and features.
Difference between outer and inner planets
The distance between planets and sizes of the planets vary greatly. The outer, "gas" planets are very large, and the four inner planets are comparatively small and rocky.
A force that keeps the planets in motion around the sun. Gravity acts everywhere in the universe.
What revolves around what in space?
Planets revolve around the sun, and moons revolve around planets. A planet rotates upon an axis.
A dwarf planet
revolves around the sun, and can maintain a nearly round shape as planets do, but it cannot move other objects away from its orbital neighborhood.
What causes day and night?
As Earth rotates, different sides of Earth face toward or away from the sun, thus causing day and night, respectively.
What causes the phases of the moon?
The phases of the moon are caused by its position relative to Earth and the sun.
Main characteristics of earth.
Earth is a rocky planet, extensively covered with large oceans of liquid water and having frozen ice caps in its polar regions. Earth has a protective atmosphere consisting predominantly of nitrogen and oxygen and has a magnetic field. The atmosphere and the magnetic field help shield Earth's surface from harmful solar radiation. Scientific evidence indicates that Earth is about 4.5 billion years old.
What causes seasons?
Seasons are caused by a combination of the tilt of Earth on its axis, the curvature of Earth's surface and, thus, the angle at which sunlight strikes the surface of Earth during its annual revolution around the sun.
What causes tides?
Tides are the result of the gravitational pull of the moon and sun on the surface waters of Earth.
Whose ideas contributed to our understanding of the solar system?
The ideas of Ptolemy, Aristotle, Copernicus, and Galileo contributed to the development of our understanding of the solar system.
Why has our knowledge of the solar system has increased substantially?
With the development of new technology over the last half-century,
What does life depend on?
People, as well as other living organisms, are dependent upon the availability of clean water and air and a healthy environment.
What role doe local, state, and federal governments have with respect to the environment?
They have significant roles in managing and protecting air, water, plant, and wildlife resources.
Modern industrial society is dependent upon
Fossil fuels
the major sources of energy in developed and industrialized nations and should be managed to minimize adverse impacts.
What is sustainable development?
Renewable resources should be managed so that they produce continuously. Sustainable development makes decisions about long-term use of the land and natural resources for maximum community benefit for the longest time and with the least environmental damage.
What helps conserve resources and protect the environment?
Regulations, incentives, and voluntary efforts help conserve resources and protect environmental quality.
Conservation of resources and environmental protection begin with...
individual acts of stewardship.
Use of renewable (water, air, soil, plant life, animal life) and nonrenewable resources (coal, oil, natural gas, nuclear power, and mineral resources) must be considered in terms of
their cost/benefit tradeoffs.
Environmental Preventive measures do what?
such as pollution prevention or thoughtfully planned and enforced land-use restrictions, can reduce the impact of potential problems in the future.
Pollution prevention and waste management are...
less costly than cleanup.
Division of labor within a cell is...
essential to the overall successful function of the cell.
Similarities and differences in plants and animals are...
evident at the cellular level. Plant and animal cells contain some of the same organelles and some that differ.
The original cell theory includes what components:
all living things are composed of cells; cells are the smallest unit (structure) of living things that can perform the processes (functions) necessary for life; and living cells come only from other living cells.
The development of the original cell theory can be attributed to...
the major discoveries of many notable scientists. The development of the cell theory has been dependent upon improvements in the microscope and microscopic techniques throughout the last four centuries. Continuing advances in microscopes and instrumentation have increased the understanding of cell organelles and their functions. Many of these organelles can now be observed with a microscope (light, electron).
What is the cell cycle.
The phases of the cell cycle are interphase, mitosis, and cytokinesis.
The purpose of mitosis is
to produce new cells for growth and repair that are identical to the parent cell. The purpose of meiosis is to produce reproductive (sex) cells that carry half the genetic material of the parent.
Relationship between cells, tissues and organs
Cells that have the same function group together to form tissues. Tissues that have the same function group together to form organs. Organs with similar functions group to work together in an organ system.
Unicellular organisms
made of only one cell.
Multicellular organisms
made of many cells.
Multicellular organisms exhibit...
a hierarchy of cellular organization. They are complex in that there is a division of labor among the levels of this hierarchy for carrying out necessary life processes.
Cells perform what functions and processes?
cellular respiration, waste breakdown and removal, growth and division, and cellular transport.
the passive transport of water molecules across a cell membrane.
the passive transport of substances other than water across a cell membrane.
Living things carry out what life processes?
Ingestion, digestion and removal of waste, stimulus response, growth and repair, gas exchange, and reproduction.
How are living things categorized?
Information about physical features and activities is arranged in a hierarchy of increasing specificity. The levels in the accepted hierarchy include domain, kingdom, phylum, class, order, family, genus and species.
Current classification systems now generally recognize the categorization of organisms into what three domains?
Archaea, Bacteria and Eukarya.
Some important animal groups (phyla) are
the cnidarians, mollusks, annelids, arthropods, echinoderms, and chordates.
Four important plant groups (divisions) are
the mosses, ferns, conifers, and flowering plants.
A species
A group of similar-looking organisms that can interbreed under natural conditions and produce offspring that are capable of reproduction defines a species.
A chemical in chloroplasts that can absorb or trap light energy.
The necessary life process that transforms light energy into chemical energy. It involves a series of chemical reactions in which the light energy is used to change raw materials (carbon dioxide and water) into products (sugar and oxygen). The energy is stored in the chemical bonds of the glucose (sugar) molecules.
Function of plants
Plants convert the sugars they produce into other raw materials that are used by plants and animals for growth, repair, and energy needs.
Why are photosynthesizing organisms called producers?
Photosynthesizing organisms obtain their energy from the sun and are often called producers because of their ability to produce glucose (sugar). photosynthesizing organisms are the foundation of virtually all food webs.
What do decomposers do?
Materials are recycled and made available through the action of decomposers.
Describe how energy passes through a food web?
Energy enters an ecosystem through the process of photosynthesis and is passed through the system as one organism eats and is, in turn, eaten. This energy flow can be modeled through relationships expressed in food webs.
Energy pyramid for foodwebs
The amount of energy available to each successive trophic level (producer, first-order consumer, second-order consumer, third-order consumer) decreases. This can be modeled through an energy pyramid, in which the producers provide the broad base that supports the other interactions in the system.
How do individual members of a population interact with each other?
These interactions include competing with each other for basic resources, mates, territory, and cooperating with each other to meet basic needs.
The establishment of a social order in a population may ensure...
that labor and resources are adequately shared.
The establishment of a territory ensures that...
members of a population have adequate habitat to provide for basic resources.
Interdependent communities
Organisms or populations that rely on each other for basic needs form interdependent communities.
Energy resources of a community are shared through...
the interactions of producers, consumers, and decomposers.
predator-prey relationship
The interaction between a consumer that hunts for another consumer for food.
Relationship between organisms, population and community
Organisms may exist as members of a population; populations interact with other populations in a community.
How do populations interact in a community?
Populations of one species may compete with populations of other species for resources. Populations of one species may also cooperate with populations of other species for resources.
Symbiotic relationship
A relationship between two or more organisms of different species when they live and work together.
Types of symbiotic relationships include...
mutualism (in which both organisms benefit), commensalism (in which one organism benefits and the other is unaffected), and parasitism (in which one organism benefits and the other is harmed).