Nara Public High School Entrance Examination - Science flashcards

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

Velocity

A vector quantity: speed in a stated direction. Two objects can have equal speeds but different velocities, and a round trip has average velocity of zero.

Newton's second law

The net force on an object equals its mass times its acceleration (F = ma). Acceleration points in the direction of the net force, and larger mass means smaller acceleration.

Terminal velocity

The constant speed reached by a falling object when upward air resistance exactly balances its weight. Net force becomes zero, so acceleration stops and speed stays steady.

Pressure

Force per unit area, measured in pascals (N/m²). A given force produces greater pressure when applied over a smaller area, which is why sharp edges cut easily.

Kinetic energy

Energy of motion, calculated as ½mv². Doubling the speed multiplies kinetic energy by four, so braking distance grows much faster than speed.

Wave equation

Wave speed equals frequency multiplied by wavelength (v = fλ). Frequency is fixed by the source, so wavelength shortens when a wave slows in a denser medium.

Ohm's law

Current through a conductor is proportional to voltage across it (V = IR). Resistance rises with longer, thinner, or hotter wires and falls when the cross-section is larger.

Series and parallel

In series, current is identical everywhere and voltages add. In parallel, voltage is identical across branches and branch currents add, giving lower total resistance.

Electrical power

Rate of energy transfer, P = VI = I²R = V²/R, measured in watts. Energy consumed equals power multiplied by time, often billed in kilowatt-hours.

Pure substance versus mixture

A pure substance melts and boils at fixed temperatures. A mixture melts over a range, its components keep their own properties, and it can be separated by physical methods.

Chemical change

A change producing new substances with different properties. Evidence includes gas release, precipitate formation, unexpected colour change, heat release, or light emission.

Distillation

Separation by boiling point. The liquid with the lower boiling point vaporises first and is condensed and collected, leaving less volatile substances behind in the flask.

Neutralisation

Reaction of an acid with a base producing a salt and water. Hydrogen ions and hydroxide ions combine, so the pH moves toward neutral and temperature usually rises.

Atomic number

The number of protons in an atom's nucleus. It defines the element and equals the electron count in a neutral atom; in ions, electrons differ but protons do not.

Ion formation

Atoms gain or lose electrons to gain a full outer shell. Metal atoms lose electrons forming positive ions; non-metal atoms gain electrons forming negative ions.

Balancing equations

Adjusting coefficients so each element has equal atoms on both sides, respecting conservation of mass. Subscripts inside formulas must never be altered to balance.

The mole

Amount of substance containing 6.0 × 10²³ particles. Its mass in grams equals the molar mass, the sum of atomic masses in the formula.

Exothermic reaction

A reaction releasing heat to the surroundings, so the mixture's temperature rises. Combustion and neutralisation are examples; the products hold less chemical energy than the reactants.

Food chain energy loss

Only about ten percent of energy passes to the next trophic level. Most is lost as heat through respiration, so food chains rarely exceed four or five links.

Decomposers

Organisms such as fungi and bacteria that break down dead bodies and waste. They release minerals back into the soil, recycling matter while energy flows one way.

Mutualism

A symbiotic relationship in which both species benefit, such as a bee gaining nectar while pollinating a flower. Neither partner is harmed by the association.

Carrying capacity

The maximum population an environment can sustain. Limited food, space, water, and predators set the limit, and growth slows as the population approaches it.

Photosynthesis

Carbon dioxide plus water, using light energy and chlorophyll, produces glucose and oxygen in chloroplasts. It stores light energy as chemical energy in organic molecules.

Cellular respiration

Glucose plus oxygen yields carbon dioxide, water, and usable energy in mitochondria. It occurs in all living cells continuously, including in darkness.

Mitosis versus meiosis

Mitosis makes two genetically identical body cells for growth and repair. Meiosis makes gametes with half the chromosome number, creating genetic variation.

Xylem and phloem

Xylem vessels carry water and dissolved minerals upward from roots to leaves. Phloem tubes carry sugars made in leaves to growing and storage tissues.

Plate boundaries

Divergent boundaries form mid-ocean ridges; convergent boundaries form mountains, trenches, and volcanoes; transform boundaries produce earthquakes as plates slide past.

Igneous rock

Rock formed when magma or lava cools and solidifies. Slow cooling underground gives large crystals; rapid cooling at the surface gives fine crystals or glass.

Cold front

The leading edge of advancing cold air pushing under warm air. It brings brief heavy rain, gusty winds, and a sharp temperature drop as it passes.

Causes of seasons

Earth's axis tilts about 23.4° from vertical. As Earth orbits, each hemisphere receives sunlight at a steeper angle and for longer in its summer.

Control group

The comparison group in an experiment that receives no treatment or a standard treatment. It shows what would happen without the independent variable.

Independent variable

The factor deliberately changed by the experimenter. It is plotted on the horizontal axis, while the dependent variable, which is measured, goes on the vertical axis.