MCAS Grade 8 Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Speed formula

Speed equals distance traveled divided by time elapsed. It describes how fast position changes and does not include direction, unlike velocity.

Velocity vs. speed

Velocity is speed in a stated direction, so it is a vector quantity. A car going 30 km/h north and one going 30 km/h south have equal speeds but different velocities.

Acceleration

Acceleration is the rate of change of velocity, calculated as change in velocity divided by time. It occurs when an object speeds up, slows down, or changes direction.

Newton's first law

An object at rest stays at rest and an object in motion continues in a straight line at constant speed unless a net outside force acts on it. This is inertia.

Newton's second law

Net force equals mass times acceleration (F = ma). For the same force, a larger mass accelerates less; for the same mass, a larger net force produces greater acceleration.

Newton's third law

For every action force there is an equal and opposite reaction force. The two forces act on different objects, which is why they do not cancel out.

Mass vs. weight

Mass is the amount of matter in an object and stays constant. Weight is the gravitational force on that mass and changes when gravity changes, such as on the Moon.

Kinetic energy

Kinetic energy is energy of motion, calculated as one-half mass times speed squared. Because speed is squared, doubling speed increases kinetic energy four times.

Potential energy

Potential energy is stored energy due to position or arrangement. Gravitational potential energy increases with height and mass; a raised object gains it and releases it as it falls.

Conservation of energy

Energy cannot be created or destroyed, only transferred or transformed between forms. In real systems, friction converts some mechanical energy into thermal energy that spreads into the surroundings.

Wave speed relationship

Wave speed equals frequency multiplied by wavelength. For a wave traveling at constant speed through a medium, higher frequency means shorter wavelength and vice versa.

Series circuit

A circuit with a single path for current. Current is the same through every component, and if one component breaks or is removed, the entire circuit stops working.

Parallel circuit

A circuit with two or more separate branches. Current splits among branches, each branch can operate independently, and adding branches decreases total resistance and increases total current.

Electromagnet

A magnet created by current flowing through a coil of wire, often wrapped around an iron core. Its strength increases with more current, more coil turns, and a suitable core.

Conduction vs. convection

Conduction transfers thermal energy through direct contact between particles. Convection transfers thermal energy by movement of fluids, where warmer, less dense material rises and cooler material sinks.

Radiation

Radiation transfers energy by electromagnetic waves and does not require a medium. It is how energy from the Sun reaches Earth through the vacuum of space.

Reflection vs. refraction

Reflection is light bouncing off a surface at an angle equal to the incoming angle. Refraction is light bending as it passes between materials where its speed changes.

Law of superposition

In undisturbed sedimentary rock layers, older layers lie below younger layers. This principle lets geologists determine the relative ages of rock formations and fossils within them.

Plate tectonics

Earth's lithosphere is broken into plates that move over the mantle. Their interactions at boundaries cause earthquakes, volcanic activity, mountain building, and seafloor spreading.

Divergent boundary

A boundary where two plates move apart. Magma rises to fill the gap, forming new crust, as at mid-ocean ridges, and causing shallow earthquakes and volcanic activity.

Convergent boundary

A boundary where plates move toward each other. Oceanic crust may subduct beneath another plate, producing deep earthquakes, volcanoes, and mountain ranges like the Andes.

Transform boundary

A boundary where plates slide past each other horizontally. Crust is neither created nor destroyed, but stress builds and releases as earthquakes, as along the San Andreas Fault.

Rock cycle

The continuous process by which igneous, sedimentary, and metamorphic rocks change from one type to another through melting, cooling, weathering, erosion, compaction, and heat and pressure.

Weathering vs. erosion

Weathering breaks rock into smaller pieces in place through physical or chemical processes. Erosion is the transport of those pieces by water, wind, ice, or gravity.

Water cycle

The continuous movement of water among oceans, atmosphere, and land through evaporation, transpiration, condensation, precipitation, and runoff. Energy from the Sun drives the cycle.

Photosynthesis

Plants use light energy to convert carbon dioxide and water into glucose and oxygen. Chlorophyll in chloroplasts captures light, and the glucose stores chemical energy for growth.

Cellular respiration

Cells break down glucose with oxygen to release energy, producing carbon dioxide and water. This process supplies usable energy for life activities and complements photosynthesis.

Food web

A model showing feeding relationships among organisms in an ecosystem. Arrows point from the organism being eaten to the eater, tracing energy flow from producers to consumers.

Natural selection

Individuals with inherited traits better suited to their environment are more likely to survive and reproduce. Over generations, those favorable traits become more common in the population.

Adaptation

An inherited trait that improves an organism's chance of surviving and reproducing in its environment. Adaptations arise over many generations through natural selection, not by choice.

Biodiversity

The variety of living species and genetic variation in an ecosystem. Higher biodiversity generally makes an ecosystem more resilient to disturbances such as disease or environmental change.

Scientific investigation

A procedure testing a hypothesis by changing one independent variable while controlling others. Conclusions rest on repeated measurements and evidence, and results must be reproducible.