Fukuoka Entrance Science flashcards

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

Newton's second law

The net force on an object equals its mass times its acceleration (F = ma). Doubling the net force doubles acceleration; doubling the mass halves it for the same force.

Weight versus mass

Mass is the amount of matter in kilograms and does not change with location. Weight is the gravitational force on that mass, W = mg, measured in newtons.

Balanced forces

When all forces on an object cancel, the net force is zero. The object stays at rest or continues at constant velocity; this is equilibrium, not necessarily rest.

Kinetic energy

The energy of motion, calculated as one-half mass times velocity squared (KE = ½mv²). Because velocity is squared, doubling speed multiplies kinetic energy by four.

Conservation of energy

In an isolated system, energy is never created or destroyed, only converted between forms. A falling ball converts potential energy into kinetic energy and heat.

Power

The rate at which energy is transferred or work is done, measured in watts. One watt equals one joule per second; power = energy ÷ time.

Ohm's law

For a conductor at constant temperature, voltage equals current times resistance (V = IR). Increasing resistance reduces current for a fixed voltage.

Series circuit

A circuit with a single path. Current is the same through every component, voltages add to the source voltage, and total resistance is the sum of individual resistances.

Parallel circuit

A circuit with branching paths. Voltage is equal across each branch, branch currents add to the total, and total resistance is smaller than the smallest branch resistance.

Wave equation

Wave speed equals frequency multiplied by wavelength (v = fλ). Frequency is determined by the source, so it stays constant while wavelength changes with medium speed.

Sound in a vacuum

Sound is a longitudinal mechanical wave that needs particles to vibrate, so it cannot travel through a vacuum. Light can, which is why space is silent but bright.

Refraction of light

Light bends when crossing between media because its speed changes. Entering a denser, slower medium it bends toward the normal; leaving it bends away from the normal.

Convex lens images

A converging lens forms a real, inverted image when the object is beyond the focal point, and a virtual, upright, magnified image when the object is closer than the focal point.

Pure substance versus mixture

A pure substance is an element or compound with fixed composition. A mixture contains two or more substances combined physically and separable by filtration, distillation, or similar methods.

Distillation

A separation method that boils a liquid mixture and condenses the vapor. It separates liquids with different boiling points, such as water and ethanol.

Exothermic reaction

A chemical reaction that releases energy to the surroundings, usually as heat. Combustion and neutralization are exothermic; the surroundings become warmer during the reaction.

Catalyst

A substance that speeds up a reaction by lowering its activation energy but is not consumed. It does not change the overall energy released by the reaction.

Atomic number

The number of protons in an atom's nucleus, which identifies the element. In a neutral atom it also equals the number of electrons.

Isotopes

Atoms of the same element with different numbers of neutrons. They share chemical properties but have different mass numbers, such as carbon-12 and carbon-14.

pH scale

A scale from 0 to 14 measuring hydrogen ion concentration. Below 7 is acidic, 7 neutral, above 7 basic; each unit represents a tenfold change.

Neutralization reaction

An acid reacting with a base to produce a salt and water. For example, hydrochloric acid plus sodium hydroxide gives sodium chloride and water.

Balancing equations

Adjusting coefficients so each kind of atom appears in equal numbers on both sides, obeying conservation of mass. Subscripts inside formulas must never be altered to balance.

State symbols

Letters in parentheses after formulas in an equation: (s) solid, (l) liquid, (g) gas, (aq) dissolved in water. They describe the physical state of each substance.

Mitosis versus meiosis

Mitosis produces two identical diploid cells for growth and repair. Meiosis produces four genetically varied haploid gametes, halving the chromosome number before fertilization.

Photosynthesis

The process in chloroplasts where plants use light energy to convert carbon dioxide and water into glucose and oxygen. It stores energy and forms the base of most food chains.

Dominant and recessive alleles

A dominant allele is expressed even when only one copy is present. A recessive allele is expressed only when two copies are present, so it can be hidden in carriers.

Natural selection

Individuals with inherited traits suited to their environment survive and reproduce more successfully, so those traits become more common in later generations.

Energy in food chains

Only about ten percent of energy passes from one trophic level to the next, because organisms use most energy for life processes and release it as heat.

Decomposers

Organisms such as bacteria and fungi that break down dead organisms and waste, releasing nutrients like nitrogen and carbon back into the soil and atmosphere.

Plate tectonics

The theory that Earth's lithosphere is divided into rigid plates that move over the mantle. Their collisions, separations, and slides cause earthquakes, volcanoes, and mountain building.

Igneous rock

Rock formed when magma or lava cools and solidifies. Slow cooling underground produces large crystals; rapid cooling at the surface produces fine-grained rock such as basalt.

Greenhouse effect

Gases such as carbon dioxide and water vapor trap outgoing infrared radiation, warming Earth's surface. Without it Earth would be far colder than it is now.