⚡ ENERGY, WORK, UNITS & TRANSFORMATION

ENERGY

Capacity to supply heat or do work; property of a system

WORK (w)

Action of force moving object through distance; energy in transit; done by system when transferring energy to surroundings

POTENTIAL ENERGY

Energy from position, configuration, or relative arrangement of matter; includes gravitational, electrical, elastic forms

KINETIC ENERGY

Energy of motion; formula KE = ½mv²

INTERNAL ENERGY

Sum of all kinetic and potential energies of atoms/molecules within a substance; associated with molecular motion and interparticle forces

CHEMICAL ENERGY

Potential energy stored in chemical bonds; released when bond formation energy exceeds bond-breaking energy during reactions

RADIANT ENERGY

Electromagnetic energy; light/solar energy; ultimate source of most planetary energy resources

MECHANICAL ENERGY

Energy of macroscopic object movement

THERMAL ENERGY

Molecular-level kinetic energy from random motion of atoms and molecules; distinct from temperature

ELECTRICAL ENERGY

Energy from charge movement (typically electrons)

NUCLEAR ENERGY

Potential energy from proton/neutron arrangement in atomic nuclei; released via fission or fusion

TEMPERATURE

Quantitative measure of hot/cold; proportional to average molecular kinetic energy; absolute zero = theoretical minimum where molecular motion ceases

ABSOLUTE ZERO

Coldest theoretical temperature; atoms/molecules have zero kinetic energy

THERMOMETER

Device measuring temperature via thermal expansion/contraction of material

Bimetallic Thermometer

Two bonded different-metal strips (brass & steel); differential expansion/contraction causes deflection indicating temperature

HEAT (q)

Thermal energy transfer between bodies due to temperature difference; flows spontaneously from higher to lower temperature; stops at thermal equilibrium

THERMAL EQUILIBRIUM

State where two bodies in contact reach same temperature; net heat flow ceases

EXOTHERMIC PROCESS

Reaction/change releasing heat; q < 0; surroundings warm; example: combustion

ENDOTHERMIC PROCESS

Reaction/change absorbing heat; q > 0; surroundings cool; example: cold pack ammonium nitrate dissolution

PRESSURE-VOLUME WORK (PV-WORK)

Mechanical work done by expanding gas against external pressure; common in chemical processes (combustion in engines)

JOULE (J)

SI energy/work unit; 1 J = 1 kg·m²/s²

CALORIE (cal)

Energy unit; heat to raise 1 g water 14.5°C to 15.5°C; 1 cal = 4.184 J

NUTRITIONAL CALORIE (Cal)

Food energy unit; capital C; 1 Cal = 1 kcal = 1000 cal = 4184 J

BRITISH THERMAL UNIT (BTU)

Engineering energy unit; heat to raise 1 lb water by 1°F