NSEJS flashcards

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

SI unit of force

The newton (N); one newton is the force that gives a 1 kg mass an acceleration of 1 m/s², so 1 N = 1 kg·m/s².

Newton's third law

For every action force there is an equal and opposite reaction force on a different body; the two forces act on different objects, so they never cancel each other.

Conservation of momentum

In an isolated system with no external net force, total momentum before a collision equals total momentum after; this holds for both elastic and inelastic collisions.

Archimedes' principle

The buoyant force on a body immersed in fluid equals the weight of fluid displaced; a body floats when its weight is less than or equal to this buoyant force.

Ohm's law

At constant temperature, current through a conductor is directly proportional to potential difference across it: V = IR, where R is resistance in ohms.

Snell's law

When light crosses a boundary between media, n₁ sin θ₁ = n₂ sin θ₂, where n is refractive index and angles are measured from the normal.

Lens power

Power of a lens is the reciprocal of focal length in metres: P = 1/f, measured in dioptres (D); converging lenses have positive power.

Specific heat capacity

Heat needed to raise 1 kg of a substance by 1 K: Q = mcΔT. Water's high specific heat makes it a good coolant and stabiliser of climate.

Latent heat of fusion

Heat absorbed per unit mass to change a solid to liquid at its melting point without temperature change: Q = mL_f, for example about 334 J/g for ice.

Refractive index

Ratio n = c/v, comparing light speed in vacuum to that in the medium; also equals sin i / sin r for light entering the medium from air.

Mole

Amount of substance containing 6.022×10²³ (Avogadro's number) particles; one mole of any gas at STP occupies about 22.4 litres.

Molar mass

Mass in grams of one mole of a substance, numerically equal to its formula mass in atomic mass units; used to convert mass to moles via n = m/M.

Empirical formula

Simplest whole-number ratio of atoms in a compound; obtained by dividing each element's mole ratio by the smallest value, and may differ from the molecular formula.

Limiting reagent

The reactant that is completely consumed first and therefore determines the maximum amount of product formed; other reactants remain in excess.

pH scale

pH = −log[H⁺]; values below 7 are acidic, 7 is neutral at 25 °C, and above 7 is basic. Each unit change means a tenfold change in hydrogen ion concentration.

Oxidation number

A formal charge assigned to an atom assuming bonds are ionic; oxidation is an increase and reduction a decrease in this value, tracking electron transfer.

Ideal gas equation

PV = nRT relates pressure, volume, moles and absolute temperature, with R = 8.314 J/(mol·K); valid for gases at low pressure and high temperature.

Electronegativity

Tendency of an atom to attract shared electrons in a bond; it increases across a period and up a group, and large differences favour ionic bonding.

Ionisation energy

Energy required to remove the most loosely bound electron from a gaseous atom; it increases across a period and decreases down a group as atomic size grows.

Displacement reaction

A reaction in which a more reactive element displaces a less reactive one from its compound, for example zinc displacing copper from copper sulphate solution.

Aerobic respiration

Breakdown of glucose using oxygen to release energy, producing carbon dioxide and water; yields far more ATP than anaerobic respiration, roughly 36–38 per glucose.

Photosynthesis equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, driven by light energy absorbed by chlorophyll; light reactions occur in thylakoids and the Calvin cycle in the stroma.

Mitochondria

Membrane-bound organelles with folded inner cristae where aerobic respiration and ATP synthesis occur; often called the powerhouse of the cell.

Xylem and phloem

Xylem transports water and dissolved minerals upward from roots, driven by transpiration pull; phloem transports sugars bidirectionally from leaves to other plant parts.

Monohybrid cross ratio

Crossing two heterozygotes for one gene gives a 3:1 phenotypic ratio in offspring and a 1:2:1 genotypic ratio, assuming complete dominance.

Test cross

Crossing an individual of unknown genotype with a homozygous recessive partner; offspring showing the recessive trait reveal the unknown parent was heterozygous.

Nephron

Functional unit of the kidney that filters blood at the glomerulus, then reabsorbs useful substances such as glucose and water along the tubule.

Stomata

Pores mainly on leaf surfaces, opened and closed by guard cells, that allow carbon dioxide intake and oxygen release while controlling water loss by transpiration.

Arteries vs veins

Arteries carry blood away from the heart in thick elastic walls without valves; veins return blood to the heart and contain valves preventing backflow.

Enzyme specificity

Each enzyme has an active site fitting a particular substrate, like a lock and key; enzymes are biological catalysts that lower activation energy and are not consumed.

Osmosis

Net movement of water across a semipermeable membrane from lower to higher solute concentration; plant cells become turgid in hypotonic solutions and flaccid or plasmolysed in hypertonic ones.

Blood glucose regulation

Insulin from the pancreas lowers blood glucose by promoting uptake and storage as glycogen; glucagon raises it by releasing glucose, forming a negative feedback loop.