Cosmology, Motion, Evolutionary Change, and Energetics Review

Practice vocabulary flashcards covering key terms and concepts across Cosmology, Motion, Evolutionary Change, and Energetics.

Isotope

Atoms of the same element containing the same number of protons but a different number of neutrons, such as Carbon-12.

Alpha Particle

A helium nucleus composed of 2 protons and 2 neutrons ($^4_2\text{He}$) with low penetration (stopped by paper) and high ionizing ability.

Beta Particle

A high-speed electron ($^0_{-1}e$) emitted from a nucleus when a neutron decays into a proton, having medium penetration (stopped by $5\,\text{mm}$ of metal).

Gamma Ray

High-energy electromagnetic radiation emitted from an unstable nucleus that has no mass, low ionizing ability, and high penetration requiring lead to block.

Half-Life

The time required for half the radioactive nuclei in a sample to decay, calculated using the fraction remaining formula $(\frac{1}{2})^n$, where $n = \frac{\text{time}}{\text{half-life}}$.

Nuclear Fission

A nuclear process where a heavy nucleus absorbs a neutron and splits into smaller nuclei, additional neutrons, and energy, driving a chain reaction in power plants.

Nuclear Fusion

A nuclear process where light nuclei join together under extreme heat and pressure to form a heavier nucleus and release energy ($E = mc^2$), powering stars.

Cobalt-60

A radioisotope used in medical radiotherapy for cancer treatment and for sterilizing medical equipment.

Americium-241

An alpha-emitting radioisotope utilized in industrial smoke detectors.

Thallium-204

A beta-emitting radioisotope used in industry inside thickness gauges.

Tritium

A radioisotope utilized in environmental science for tracing water movement and pollution.

Astronomical Unit (AU)

A unit of length defined as the average distance between the Earth and the Sun, utilized for distances inside the solar system.

Light Year

A unit of astronomical distance defined as the distance light travels in one year, used for measurements between stars and galaxies.

Main Sequence

The diagonal band on a Hertzsprung-Russell diagram containing approximately $90\%$ of stars, where gravitational collapse is balanced by core hydrogen fusion.

Hubble's Law

The observation that distant galaxies are moving away from Earth with a recession velocity proportional to their distance ($v = H_0 d$), showing that the universe is expanding.

Cosmic Microwave Background Radiation (CMBR)

A uniform microwave radiation signal arriving from all directions, discovered by Penzias and Wilson in 1963 as leftover thermal radiation from the early universe.

Planck Time

The earliest time boundary ($5 \times 10^{-44}\,\text{s}$ after the Big Bang) before which modern physics cannot describe events because the four fundamental forces were unified.

CRAAP Test

An evaluative checklist used to assess the validity of online claims and content based on Currency, Relevance, Authority, Accuracy, and Purpose.

Scalar

A physical quantity that has magnitude only and no direction, such as distance, speed, time, mass, and energy.

Vector

A physical quantity that possesses both magnitude and direction, such as displacement, velocity, acceleration, and force.

Displacement

A vector quantity representing the straight-line distance and direction from an object's initial position to its final position.

Instantaneous Velocity

The velocity of an object at a specific single point in time, given by the gradient of a displacement-time graph.

Acceleration

The rate of change in velocity over time, measured in $\text{m/s}^2$ and represented by the gradient of a velocity-time graph.

Newton's First Law

The principle stating that an object remains at rest or travels at a constant velocity unless acted upon by unbalanced net forces.

Net Force

The overall vector sum of all individual forces acting upon an object, where opposing forces subtract from each other.

Newton's Second Law

The law stating that unbalanced forces cause acceleration proportional to the net force and inversely proportional to the object's mass.

Newton's Third Law

The principle stating that when object A exerts a force on object B, object B exerts an equal and opposite force on object A, acting on different objects.

Weight

The gravitational force acting upon an object's mass, calculated as a vector quantity using $\text{Weight} = \text{mass} \times g$ and measured in newtons ($\text{N}$).

Adaptation

A structural, physiological, or behavioural trait that enhances an organism's survival and reproductive success in its environment.

VERA

An acronym summarizing natural selection: Variation (heritable population differences), Environmental pressure (differential survival), Reproduction (passing favourable traits), and Adaptation (gradual species change).

Wallace's Line

A faunal boundary line drawn in Southeast Asia by Alfred Wallace separating distinct Asian and Australian animal groups.

Speciation

The evolutionary process occurring when isolated populations diverge under differing selection pressures to form distinct new species.

Lamarckism

The disproven hypothesis stating that traits acquired or modified through use or disuse during an organism's lifetime can be inherited by its offspring.

Homologous Structures

Anatomical structures derived from a common ancestor that share the same basic skeletal layout despite having different functions, such as the pentadactyl limb.

Transitional Form

A fossil organism exhibiting anatomical traits common to both an ancestral group and its derived descendant group, such as Archaeopteryx or Tiktaalik.

Germline Mutation

A genetic mutation occurring in reproductive gametes that creates new alleles and can be inherited by offspring.

Endothermic Reaction

A chemical change that absorbs thermal energy from the surroundings, associated with bond breaking and a positive enthalpy change ($\Delta H > 0$).

Exothermic Reaction

A chemical change that releases thermal energy into the surroundings, associated with bond formation and a negative enthalpy change ($\Delta H < 0$).

Enthalpy Change ($\Delta H$)

The net heat energy absorbed or released per mole of a reacting substance, expressed in units of $\text{kJ}\,\text{mol}^{-1}$.

Activation Energy

The minimum kinetic energy barrier that colliding particles must possess in order to separate bonds and undergo a chemical reaction.

Collision Theory

The model stating that a chemical reaction requires reactant particles to collide with the correct spatial orientation and energy exceeding the activation energy.

Catalyst

A chemical substance that accelerates reaction rate by providing an alternative reaction pathway with lower activation energy without being consumed.