Science exam 2.0

current

What is predation?

A biological interaction where one organism hunts; kills; and consumes another organism for energy. It acts as a major population control mechanism in ecosystems.

What is symbiosis?

A close long-term relationship between two different species living together. It includes mutualism; commensalism; and parasitism.

What is the biosphere?

The thin life-supporting zone of the Earth that includes all living organisms interacting with the physical environment spanning from the deepest ocean trenches to the lower atmosphere.

What is the role of nuclear fusion in ecosystems?

The process powering the Sun where hydrogen atoms fuse into helium under extreme heat and pressure. This releases massive light and thermal energy which serves as the ultimate source of energy for almost all life on Earth.

What is photosynthesis?

The chemical process used by plants and algae to convert light energy; carbon dioxide; and water into chemical energy and oxygen gas. Equation: 6CO2 + 6H2O + Light Energy -> C6H12O6 + 6O2.

What is a trophic level?

The specific feeding position or level that an organism occupies in a food chain or ecological pyramid such as producer; primary consumer; or secondary consumer.

What is sustainability?

The ability of an ecosystem to maintain its structural balance; biodiversity; and processes over time without depleting resources or collapsing due to environmental pressures.

What is a producer?

An autotrophic organism that produces its own food using energy from the Sun through photosynthesis forming the base of all food chains.

What is a primary consumer?

A herbivorous or omnivorous animal that gets its energy by feeding directly on primary producers.

What is a secondary consumer?

A carnivorous or omnivorous animal that gets its energy by feeding on primary consumers.

What is a tertiary consumer?

An apex predator that sits at the top of the food chain and gets its energy by feeding on secondary consumers.

What is cellular respiration?

The chemical process by which cells break down glucose using oxygen to release usable energy for survival producing carbon dioxide and water as waste. Equation: C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP Energy.

What are greenhouse gases?

Atmospheric gases like carbon dioxide; methane; nitrous oxide; and water vapor that trap heat energy radiated from the Earth surface keeping the planet warm via the greenhouse effect.

What is an ecological niche?

The complete role and position a species has in its environment including its habitat; what it eats; what eats it; and how it behaves and interacts with biotic and abiotic factors.

What is biodiversity?

The variety of life found in a particular ecosystem or on the entire planet usually measured by genetic diversity; species diversity; and ecosystem diversity.

What is extinction?

The permanent disappearance of a species from Earth when the very last individual of that species dies.

What does endangered mean?

A status given to a species that is facing an exceptionally high risk of extinction in the wild in the near future due to rapid population drop or habitat loss.

What is captive breeding?

The practice of breeding endangered species in controlled human-managed environments like zoos or sanctuaries to increase their numbers and eventually reintroduce them into the wild.

What is eutrophication?

The process where a body of water becomes overly enriched with nutrients causing massive algae blooms that block sunlight; consume oxygen when they decompose; and suffocate aquatic life.

What are the roles of producers consumers predators and decomposers in food chains?

Producers capture solar energy to make food. Consumers eat other organisms to transfer energy up the chain. Predators control the populations of prey to prevent overgrazing. Decomposers break down dead organic matter to recycle nutrients back into the soil.

How do you identify producers primary consumers and secondary consumers in a food chain?

Look at the direction of the arrows which show energy flow. In [Grass -> Cricket -> Frog] Grass is the producer; Cricket is the primary consumer; and Frog is the secondary consumer.

How are ecosystem relationships represented by food chains and food webs?

A food chain is a single direct path showing who eats whom. A food web is a network of many interconnected food chains which more realistically represents the complex feeding relationships in an ecosystem.

How does the length of a food chain relate to the amount of energy available?

Food chains are short because only about 10% of energy is passed from one trophic level to the next. The other 90% is lost as heat or used up by the organism for survival leaving too little energy to support higher levels.

How do energy and nutrients flow differently through an ecosystem?

Energy flows in a one-way path through an ecosystem entering from the Sun and eventually leaving as waste heat. Nutrients are limited and must be constantly recycled over and over through biogeochemical cycles.

How do photosynthesis and cellular respiration compare using equations?

They are chemical opposites. Photosynthesis stores energy by turning carbon dioxide and water into glucose and oxygen (6CO2 + 6H2O + Light -> C6H12O6 + 6O2). Cellular respiration releases energy by breaking down glucose and oxygen into carbon dioxide and water (C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy).

How do you explain a predator-prey relationship graph?

The graph shows two cycling lines where the predator population peaks slightly after the prey population. When prey increases; predators get more food and increase later; when predators get too high; they eat too many prey causing the prey to crash which soon causes the predator population to crash due to starvation.

What is an ecological footprint and how do human activities leave one?

An ecological footprint measures how much land and water area a human or population requires to produce the resources they consume and absorb their waste. Activities like driving cars; burning coal; clearing forests; and creating plastic garbage expand our footprint.

How are invasive species introduced and how can they be controlled?

They are introduced to new areas intentionally or accidentally. They can be controlled through physical removal; chemical treatments; or biological control.

How does burning fossil fuels cause climate change?

Burning fossil fuels releases large amounts of stored carbon dioxide into the atmosphere. This excess CO2 increases the concentration of greenhouse gases trapping more heat in the atmosphere and causing global temperatures to rise.

What is an element?

A pure substance made up of only one type of atom that cannot be broken down into simpler substances by chemical means.

What is a compound?

A pure substance made of two or more different types of elements that are chemically bonded together in fixed proportions.

What is density?

A physical property of matter that describes how much mass is packed into a specific volume. Formula: Density = Mass / Volume.

What is a positive charge?

The electrical charge held by protons or the overall charge of an atom that has lost electrons.

What is a negative charge?

The electrical charge held by electrons or the overall charge of an atom that has gained electrons.

What is a proton?

A positively charged subatomic particle found inside the nucleus of an atom with a relative mass of 1.

What is a neutron?

A neutral subatomic particle found inside the nucleus of an atom with a relative mass of 1.

What is an electron?

A negatively charged subatomic particle that orbits outside the nucleus in electron shells with an extremely tiny negligible mass.

What is atomic mass?

The total average mass of an atom calculated by adding the number of protons and neutrons together in the nucleus.

What is an atomic number?

The number of protons in the nucleus of an atom which uniquely identifies what element it is.

What is a chemical symbol?

A one- or two-letter abbreviation used to represent an element on the periodic table.

What are isotopes?

Atoms of the same element that have the same number of protons but a different number of neutrons giving them a different atomic mass.

What are subatomic particles?

The smaller pieces of matter that make up an atom: protons; neutrons; and electrons.

What is the periodic table?

An organized chart of all known chemical elements arranged by increasing atomic number so that elements with similar properties fall into vertical columns.

What are metals?

Elements on the left and center of the periodic table that are typically shiny; malleable; ductile; and good conductors of heat and electricity.

What are non-metals?

Elements on the upper right side of the periodic table that are typically dull; brittle as solids; and poor conductors of heat and electricity.

What is a period on the periodic table?

A horizontal row of elements. All elements in the same period have the same number of electron shells.

What is a group on the periodic table?

A vertical column of elements. Elements in the same group share similar chemical properties because they have the same number of valence electrons.

What are valence electrons?

The electrons located in the outermost shell of an atom that are involved in forming chemical bonds.

What is an ionic bond?

A chemical bond formed when a metal atom transfers one or more electrons to a non-metal atom creating oppositely charged ions that attract each other.

What is a covalent bond?

A chemical bond formed when two non-metal atoms share pairs of valence electrons to achieve a full outer shell.

What is an ionic compound?

A compound made of metal and non-metal ions held together by strong ionic bonds in a crystal lattice structure.

What is a covalent compound?

A compound formed when non-metal atoms are held together by shared electrons in covalent bonds.

What is a molecule?

A neutral group of non-metal atoms bound tightly together by covalent bonds representing the smallest unit of a covalent compound.

What is an ion?

An atom that has gained or lost valence electrons giving it a net positive or negative electrical charge instead of being neutral.

What are the main principles of the particle theory of matter?

1 All matter is made of tiny particles. 2 All particles of a pure substance are identical. 3 There are spaces between particles. 4 Particles are always moving. 5 Particles attract each other.

How did atomic models change over time?

Dalton imagined atoms as solid indivisible billiard balls. Thomson discovered electrons. Rutherford discovered a tiny dense positive nucleus using the gold foil experiment. Bohr added that electrons orbit the nucleus in specific energy paths. The modern model views electrons in a probability cloud.

How do particles behave in solids liquids and gases during state changes?

Solids have a fixed shape and volume because particles vibrate closely in place. Liquids have a fixed volume but fluid shape because particles can slide past each other. Gases have random shape and volume because particles are far apart and move rapidly. Heating adds kinetic energy causing melting or vaporization; cooling removes energy causing condensation or freezing.

How do you solve density problems?

Use the formula Density = Mass / Volume ($D = m / V$). To find mass use $m = D \times V$. To find volume use $V = m / D$. Always make sure units line up like grams and milliliters.

How do you test for oxygen hydrogen carbon dioxide and water gases?

Oxygen: Collect oxygen in a test tube, hold glowing splint to the neck if oxygen it present, splint re-lights splint.

Hydrogen: Put hydrogen in a test tube, light a wooden splint and place it near the neck. If hydrogen is present it makes a loud pop sound.

Carbon Dioxide: Collect co2 in a balloon, mix co2 with limewater, if co2 is present clear limewater will turn cloudy

Water: breath onto a piece of coblat chloride paper. If water is present cobalt chloride paper turns pink.

How do you draw Bohr-Rutherford and Lewis-dot models for elements and ions?

Bohr-Rutherford models show the nucleus with proton and neutron counts inside surrounded by rings showing all electrons. Lewis-dot models show only the element symbol surrounded by dots for its valence electrons. For ions change the electron count and put the symbol in square brackets with the charge outside.

How do you find the number of protons neutrons and electrons in an atom or ion?

Protons = Atomic Number. Electrons = same as protons if neutral. Neutrons = Atomic Mass minus Atomic Number. For ions add or subtract electrons based on the net electrical charge.

What is the difference between metals metalloids and non-metals?

Metals are on the left side; shiny; bendable; and conduct electricity. Non-metals are on the right side; dull; brittle; and insulate. Metalloids lie along the staircase line between them and share properties of both acting as partial conductors.

How do elements behave within groups and periods?

Elements in the same group behave similarly because they have the same number of outer valence electrons. Elements in the same period have their outer electrons in the same number of energy levels changing gradually across the row.

What are the characteristics of the 4 main groups of the periodic table?

Group 1 (Alkali Metals): extremely reactive soft metals. Group 2 (Alkaline Earth Metals): reactive light metals. Group 17 (Halogens): highly reactive toxic non-metals. Group 18 (Noble Gases): completely unreactive stable gases with full outer shells.

What are the trends for elements going across a period and down a group?

Going down a group atoms get larger because they add electron shells making outer electrons easier to lose. Going across a period left to right the nucleus gets more positive pulling electron shells closer.

How do atoms obtain chemical stability?

Atoms achieve stability by getting a full outer electron shell which usually means having 8 valence electrons. They do this by losing; gaining; or sharing electrons with other atoms.

What is the role of valence electrons in the reactivity of an element?

The closer an atom is to having a full outer shell the more reactive it is. Elements with 1 or 7 valence electrons are highly reactive because they only need to transfer one electron while elements with full shells are completely unreactive.

How do ionic and covalent bonds form?

Ionic bonds form when a metal atom transfers its valence electrons to a non-metal atom creating positive and negative ions that lock together by electric attraction. Covalent bonds form when two non-metal atoms both pull on shared valence electrons to fill their outer shells together.

How do ionic and covalent compounds compare in state solubility and conductivity?

Ionic compounds are brittle solid crystals at room temperature; dissolve easily in water; and conduct electricity when dissolved or melted. Covalent compounds can be solids; liquids; or gases; often do not dissolve well in water; and do not conduct electricity at all.

What is a solar eclipse?

An astronomical event that happens when the Moon passes directly between the Sun and the Earth casting a shadow on Earth surface and blocking out the Sun light.

What are celestial bodies?

Any natural objects that exist in outer space outside of Earth atmosphere including stars; planets; moons; asteroids; and comets.

What is a planet?

A large celestial body that orbits a star; is spherical due to its own gravity; and has cleared its orbital path of other large debris.

What is the umbra?

The dark central inner part of a shadow where all light from the light source is completely blocked out.

What is the penumbra?

The lighter outer part of a shadow that surrounds the dark umbra where light from the source is only partially blocked.

What is a lunar eclipse?

An astronomical event that happens when the Earth passes directly between the Sun and the Moon casting Earth shadow across the Moon and making it look dark or reddish.

What is the solar system?

A gravity-bound system consisting of a central star along with all the planets; moons; asteroids; meteoroids; and comets orbiting around it.

What is a constellation?

A distinct group or pattern of stars in the night sky that has been given a traditional name based on a mythological figure; animal; or object.

What is a comet?

A small celestial object made of ice; dust; and rock orbiting the Sun in long oval paths. When close to the Sun the ice vaporizes creating a glowing atmosphere and long tail.

What is the geocentric model?

An ancient incorrect model of the universe that placed a stationary Earth at the very center with the Sun; Moon; and planets all orbiting around it.

What is the heliocentric model?

The correct model of the solar system developed by Copernicus which places the Sun at the center with Earth and other planets orbiting around it.

What is an astronomical unit (AU)?

A unit of measurement equal to the average distance from the center of the Earth to the center of the Sun which is about 150 million kilometers.

What is an asteroid?

A small rocky celestial object orbiting the Sun mostly found inside the wide asteroid belt located between Mars and Jupiter.

What is a meteoroid?

A small chunk of rock or metal debris moving through outer space varying in size from a grain of sand to a large boulder.

What is a meteor?

A meteoroid that enters Earth atmosphere at high speed and burns up due to friction with air molecules creating a bright streak of light across the sky.

What is a meteorite?

A piece of a meteoroid that survives its hot trip through Earth atmosphere and actually hits the ground.

What is the solar nebula theory?

The scientific theory that our solar system formed about 4.6 billion years ago from the gravitational collapse of a giant spinning cloud of interstellar gas and dust.

What is a nebula?

A massive interstellar cloud of gas and dust in space often acting as a stellar nursery where new stars are born.

What is a protostar?

A warm dense mass of gas inside a collapsing nebula that is gathering material to become a star before nuclear fusion begins in its core.

What is a star?

A massive glowing ball of hot plasma held together by its own gravity generating its own light and heat through nuclear fusion in its core.

What is luminosity?

The total amount of energy or light emitted by a star into space per second which measures its true brightness regardless of how far away it is from Earth.

What is an H-R (Hertzsprung-Russell) diagram?

A scatter plot graph for stars that compares their absolute brightness on the vertical axis against their surface temperature or color on the horizontal axis used to study stellar lifecycles.

What are main sequence stars?

Stars that are in the longest most stable stage of their life cycle actively fusing hydrogen into helium in their cores. The Sun is currently a main sequence star.

What is a white dwarf?

The hot dead dense core remnant left behind after a low-to-medium mass star sheds its outer layers at the end of its life cycle. It no longer undergoes fusion.

What is a red giant?

A large bright star with a cool surface that forms when a main sequence star runs out of hydrogen in its core causing the core to collapse and the outer layers to puff out and cool.

What is a supernova?

A cataclysmic incredibly bright explosion of a dying massive star triggered when its core collapses which scatters heavy elements across space.

What is a sunspot?

A temporary dark cooler region on the Sun surface caused by intense magnetic activity that blocks the upward flow of hot gas.

What is a neutron star?

The extremely tiny incredibly dense remnant core of a massive star that collapsed during a supernova composed entirely of tightly packed neutrons.

What is a black hole?

An object in space with a gravitational pull so incredibly strong that nothing can escape from it formed by the collapse of the most massive stars.

What is the Milky Way?

The large barred-spiral galaxy that contains our solar system along with hundreds of billions of other stars; dust; and gas clouds.

What is a galaxy?

A massive system holding billions of stars; gas; dust; and dark matter bound securely together by gravitational forces.