8th Grade Science Quiz

Photosynthesis and Cellular Respiration

• Photosynthesis is the process by which certain organisms convert light energy into chemical energy stored in glucose.

• The word equation for photosynthesis is: Carbon dioxide + Water + Light energy → Glucose + Oxygen.

• The reactants for photosynthesis are carbon dioxide, water, and light energy.

• The products of photosynthesis are glucose and oxygen.

• Cellular respiration is the process by which organisms break down glucose to release energy (ATP).

• The word equation for cellular respiration is: Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP).

• The reactants for cellular respiration are glucose and oxygen.

• The products of cellular respiration are carbon dioxide, water, and ATP.

• Photosynthesis and cellular respiration are related in a cycle. The products of photosynthesis (glucose and oxygen) are used as reactants in cellular respiration. Conversely, the products of cellular respiration (carbon dioxide and water) are used as reactants in photosynthesis. This cycle maintains the balance of gases and energy in the atmosphere.

• Photosynthesis occurs in plants, algae, and some bacteria.

• Cellular respiration takes place in all living organisms, including plants, animals, fungi, and bacteria.

Trophic Levels

• Producers are organisms that create energy-rich compounds via photosynthesis (e.g., plants, algae).
• Primary consumers are herbivores that feed on producers (e.g., rabbits, deer).
• Secondary consumers are carnivores or omnivores that feed on primary consumers (e.g., snakes, foxes).

Types of Interactions

• Parasitism: One organism benefits, the other is harmed (e.g., ticks on deer).
• Mutualism: Both organisms benefit (e.g., bees and flowers).
• Competition: Organisms compete for resources (e.g., food, habitat).
• Predation: One organism preys on another (e.g., lions hunting zebras).
• Commensalism: One organism benefits, and the other is unaffected (e.g., barnacles on whales).

Population Dynamics

• Exponential Growth: Rapid population increase under ideal conditions (J-shaped curve).
• Carrying Capacity: The maximum sustainable population size in an environment (S-shaped curve).

Invasive Species

• Invasive Species: Non-native species that disrupt ecosystems by outcompeting native species.
• Examples: Zebra mussels, kudzu vine, cane toads.

Biogeochemical Cycles

• Nitrogen Cycle: Converts nitrogen between the atmosphere, soil, and living organisms.
• Key processes include nitrogen fixation, nitrification, and denitrification.
• Phosphorus Cycle: Movement of phosphorus through rocks, soil, water, and organisms; there is no atmospheric component.

Carbon Cycle

• The carbon cycle involves the exchange of carbon among the atmosphere, oceans, soil, and living organisms via processes like photosynthesis and respiration.

Water Cycle

• The water cycle describes the continuous movement of water between the atmosphere, oceans, land, and living organisms through processes such as evaporation, condensation, precipitation, and infiltration.

Conserving Biodiversity

• Protecting habitats, establishing protected areas (national parks), reducing pollution, promoting sustainable practices, and controlling invasive species are crucial for conserving biodiversity.

Earth's Spheres

• Biosphere: All living organisms on Earth.
• Atmosphere: Gaseous layer of the Earth.
• Hydrosphere: Water bodies (oceans, lakes, rivers).
• Lithosphere: Earth's crust and landforms.

Eutrophication

• Excess nutrients (nitrogen and phosphorus) in water bodies can cause algal blooms, depleting dissolved oxygen and harming aquatic life.

Bioaccumulation and Biomagnification

• Bioaccumulation is the build-up of toxins in an organism over time, and biomagnification is the increase in toxin concentration as the toxins move up the food chain.

Biodiversity and Climate Change

• Loss of species due to habitat destruction, pollution, and climate change negatively impacts ecosystems, food security, and global health.

Restoration and Sustainability

• Initiatives like pesticide bans, recycling programs, reforestation, and renewable energy methods are examples of restoration and sustainability efforts.

Electrostatic Series

• A list of materials organized based on their tendency to gain or lose electrons.

Calculating Appliance Costs and Efficiency

• Appliance cost calculation formula: Cost=Power (kW)×Time (h)×Rate ($/kWh)
• Appliance efficiency formula: Efficiency (%) =(Total Energy Input/Useful Energy Output)×100

Ohm's Law and Circuits

• Ohm's law is expressed as V=IxR where V = Voltage, I = Current, and R = Resistance.
• Resistance means the opposition to the flow of electrons in a circuit.
• In a series circuit, current is the same throughout the circuit, while voltage is divided across different components in the circuit.
• In a parallel circuit, voltage is the same across each branch, while current divides across the branches.

Ways to Save Energy

• Use more energy-efficient appliances.
• Unplug devices when not in use.

Renewable and Non-Renewable Energy Sources

• Renewable energy sources include solar, wind, hydroelectric, geothermal, and biomass energy.
• Non-renewable energy sources include coal, oil, natural gas, and nuclear energy.

Law of Electric Charges

• Like charges repel, and opposite charges attract.
• Electric charges can induce or transfer charges to neutral objects.

Charging an Electroscope and Grounding

• Charging an electroscope involves transferring electrons to, or from, charged objects.
• Grounding an object allows excess charge to flow to or from the Earth.

Conductors vs. Insulators

• Conductors allow electrons to flow freely, whereas insulators restrict electron flow.

Factors Affecting Resistance

• Material, length, thickness, and temperature affect resistance in a circuit.

Static Electricity vs. Current Electricity

• Static electricity involves buildup of charges, while current electricity involves continuous flow of charge through a conductor.

Atomic Theory and Key Scientists

• John Dalton proposed that atoms are indivisible.
• J.J. Thomson discovered electrons using cathode ray tubes.
• Ernest Rutherford performed the gold foil experiment, discovering the nucleus.
• Niels Bohr developed the Bohr model of the atom.

Bohr-Rutherford Diagrams

• Bohr-Rutherford diagrams show the arrangement of subatomic particles (protons, neutrons, electrons) in an atom.
• The nucleus contains protons and neutrons, and electrons orbit the nucleus in specific energy levels.

Counting Atoms in a Compound

• Standard atomic notation is used to represent atoms and molecules.

Determining Atomic Details

• Atomic number represents the number of protons in an atom.
• Mass number represents the sum of protons and neutrons.

Reactivity and Atomic Structure

• Reactivity of elements depends on their location in the periodic table, particularly in their groups and periods.

Particle Theory of Matter

• Matter is composed of tiny particles that are in constant motion and are attracted to one another.

Physical and Chemical Properties

• Physical properties are measurable (e.g., density, melting point), while chemical properties describe a substance's ability to react (e.g., flammability, reactivity with acid).

Subatomic Particles

• Protons are positively charged, neutrons have no charge, and electrons are negatively charged.

Families of Elements

• Alkali metals (Group 1), alkaline earth metals (Group 2), halogens (Group 17), and noble gases (Group 18) are families of elements with similar properties.

Ions and Their Formation

• Cations (positive ions) are formed when an atom loses electrons, and anions (negative ions) are formed when an atom gains electrons.

Classification of Matter

• Mixtures are combinations of two or more substances that retain their individual properties; they are either homogenous (uniform) or heterogeneous (not uniform).
• Pure substances have a fixed composition, are either elements or compounds.
• Elements are made of one type of atom, and compounds are made of two or more elements chemically bonded.

Density

• Density is defined as mass per unit volume. Mathematically, Density = Mass / Volume

Drawing Common Compounds

• Compounds are composed of atoms bonded chemically.
• Example of compounds is water (H₂O).

Pure Substances vs. Mixtures, Elements vs. Compounds

• Pure substances have uniform properties throughout and are either elements or compounds.
• Mixtures are combinations of substances that retain their individual properties.
• Elements are made of one type of atom, compounds are chemically bonded elements.

Importance of Earth's Tilt

• Earth's tilt on its axis causes seasonal variations in sunlight, resulting in different weather patterns around the planet.

Inner Planets vs. Outer Planets

• Characteristics of inner planets (Mercury, Venus, Earth, Mars) include small size, rocky surfaces and few, or no moons.
• Characteristics of outer planets (Jupiter, Saturn, Uranus, Neptune) include large size, gaseous composition, many moons, and are far from the Sun.

Canadian Contributions to Space Exploration

• Canadians have contributed significantly to space exploration, developing robotic arms (Canadarm, Canadarm2) and making contributions to satellite technology.

Why Pluto is Considered a Dwarf Planet

• Pluto does not meet current criteria for classifying an object as a planet, which requires clearing its orbit of other objects.

Challenges and Hazards Astronauts Face

• Astronauts face challenges such as microgravity, radiation, psychological stress, and health issues during space missions.

Definition of Celestial Object

• Celestial objects are natural objects found in space, such as stars, planets, moons, asteroids, comets, and galaxies.

Earth's Rotation and Revolution

• Earth rotates on its axis once every 24 hours causing day and night.
• Earth orbits the Sun every 365.25 days, and its tilted axis causes seasons.

Astronomical Unit

• An Astronomical Unit (AU) is a unit of measurement representing the average distance between Earth and the Sun.

Asteroid Belt

• The asteroid belt is located between Mars and Jupiter, containing rocky remnants from the early solar system, including planetesimals.

Constellations

• Constellations are patterns of stars in the night sky, which have significant importance in navigation, timekeeping, and cultural significance.

Why Ancient Cultures Studied the Skies

• Ancient cultures studied the sky for navigation, timekeeping, and religious or cultural reasons.

Lunar vs Solar Eclipse

• Lunar eclipses occur when Earth passes between the Sun and Moon, casting a shadow on the Moon, and solar eclipses occur when the Moon passes between the Sun and Earth, casting a shadow on the Earth.

Big Bang Theory vs Solar Nebula Theory

• The Big Bang Theory describes the origin and evolution of the universe.
• The Solar Nebula Theory explains the formation of our solar system.

Test your knowledge on various science concepts including solar system formation, chemical reactions, and properties of atoms. This quiz covers topics such as the distance from the Earth to the Sun, the reactivity of halogens, and the characteristics of different mixtures. Are you ready to challenge yourself?