Aichi 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. Force is in newtons, mass in kilograms, and acceleration in metres per second squared.

Conservation of energy

Energy is neither created nor destroyed, only transferred between stores. In a falling object, gravitational potential energy converts to kinetic energy, with some lost to heat and sound.

Momentum

Momentum equals mass times velocity, p = mv, measured in kilogram metres per second. In a closed system the total momentum before a collision equals the total after.

Friction

A force opposing relative motion between surfaces in contact. Static friction adjusts up to a maximum before sliding starts; kinetic friction then acts at roughly constant size.

Ohm's law

For a conductor at constant temperature, the current through it is proportional to the potential difference across it, so V = IR. Resistance is measured in ohms.

Series and parallel resistance

In series, resistances add directly. In parallel, the reciprocals add, so total resistance is less than the smallest individual resistance.

Electromagnetic induction

A changing magnetic field through a coil induces a voltage in it. Generators use this effect, and the induced voltage increases with faster movement or more coil turns.

Wave equation

Wave speed equals frequency multiplied by wavelength, v = fλ. Frequency is fixed by the source, while speed and wavelength change when the wave enters a different medium.

Sound in a vacuum

Sound is a longitudinal wave of compressions and rarefactions and needs a material medium. It cannot travel through a vacuum, which is why space is silent.

Distillation

A separation method that boils a mixture and condenses the vapour. It separates liquids with different boiling points, such as ethanol and water, or components of petroleum.

Chromatography

A separation technique where a solvent carries dissolved substances up paper or another medium. Substances travel different distances depending on solubility, producing separate spots.

Diffusion

The net movement of particles from high to low concentration caused by random motion. It is faster in gases and at higher temperatures because particle kinetic energy is greater.

Impurity and melting point

A pure substance melts at a sharp, fixed temperature. Adding an impurity lowers the melting point and raises the boiling point, and the melting range becomes broader.

Neutralisation

The reaction of an acid with a base to give a salt and water. In ionic terms, hydrogen ions and hydroxide ions combine to form water molecules.

Oxidation and reduction

Oxidation is loss of electrons and an increase in oxidation number. Reduction is gain of electrons. The two always occur together in a redox reaction.

pH scale

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

Precipitation reaction

A reaction in which two soluble salts exchange ions to form an insoluble solid. Silver chloride and barium sulfate are common precipitates used in identification tests.

Meiosis

Cell division producing four haploid gametes from one diploid cell. It halves the chromosome number and creates new allele combinations through crossing over and independent assortment.

Dominant and recessive alleles

A dominant allele is expressed even when only one copy is present. A recessive trait is only shown when both alleles are recessive, so carriers show the dominant phenotype.

Natural selection

Individuals with inherited traits suited to their environment survive and reproduce more successfully. Over generations, those favourable alleles become more common in the population.

Mitosis

Cell division producing two genetically identical diploid daughter cells. It is used for growth, repair and asexual reproduction, and chromosome number is maintained.

Alveoli

Tiny air sacs in the lungs where gas exchange occurs. Their large total surface area, thin walls and rich blood supply allow efficient diffusion of oxygen and carbon dioxide.

Xylem and phloem

Xylem vessels carry water and dissolved minerals upward from the roots. Phloem tubes transport sugars made by photosynthesis from leaves to other parts of the plant.

Photosynthesis

The process in chloroplasts using light energy to convert carbon dioxide and water into glucose and oxygen. Chlorophyll absorbs the light, and the glucose stores chemical energy.

Energy in food chains

Energy passes from producers to consumers, but only about ten percent transfers to the next trophic level. The rest is lost as heat, movement and waste.

Transpiration

The loss of water vapour from leaves through stomata. It draws water up the xylem, is faster in warm, dry, windy, bright conditions, and can wilt plants if excessive.

Seismic waves

P-waves are longitudinal and pass through solids and liquids; S-waves are transverse and cannot pass liquids. Their behaviour reveals Earth's liquid outer core.

Plate boundaries

Places where tectonic plates meet: divergent boundaries form ridges, convergent boundaries cause subduction and mountains, and transform boundaries produce earthquakes along faults.

Superposition principle

In undisturbed sedimentary layers, deeper layers were deposited earlier and are therefore older. This allows relative dating of rock strata and their fossils.

Rock types

Igneous rock forms when magma or lava cools. Sedimentary rock forms from compacted deposits. Metamorphic rock forms when existing rock is altered by heat and pressure.

Seasons

Seasons result from Earth's axial tilt of about 23.4 degrees, which changes the angle and duration of sunlight through the year, not from changing distance to the Sun.

Air pressure and wind

Air moves from high pressure to low pressure, producing wind. Uneven solar heating creates pressure differences, and the greater the pressure gradient, the stronger the wind.