IGCSE Physics: Thermal Properties and Temperature

A complete set of vocabulary flashcards covering thermal expansion, internal energy, specific heat capacity calculations, and the mechanisms of state changes from IGCSE Physics.

Thermal Expansion

The process where materials expand as heat is added, causing molecules and atoms to move more quickly and push each other further apart.

Bimetallic Strip

A strip consisting of two metals that expand at different rates, bending by a predictable amount at a given temperature to operate temperature-activated switches.

Internal Energy

The total energy stored inside a system by its particles, composed of the sum of their kinetic energy (due to motion) and potential energy (due to relative positions).

Specific Heat Capacity ($c$)

The amount of energy required per unit mass per unit temperature increase of a substance.

Specific Heat Capacity of Copper

$$390\,J/kg\,^\circ C$$

Specific Heat Capacity of Aluminium

$$910\,J/kg\,^\circ C$$

Specific Heat Capacity of Water

$$4200\,J/kg\,^\circ C$$

Specific Heat Capacity Formula

$c = \frac{\Delta E}{m \Delta \theta}$, where $\Delta E$ is the change in thermal energy, $m$ is mass, and $\Delta \theta$ is the change in temperature.

Thermal Energy Calculation ($E$)

$E = IVt$, where $I$ is current in Amperes ($A$), $V$ is potential difference in Volts ($V$), and $t$ is time in seconds ($s$).

Melting Point

The specific temperature at which a pure substance changes from a solid to a liquid; it is the same temperature as the freezing point.

Boiling Point

The specific temperature at which a pure substance changes from a liquid to a gas.

Fixed Points of Pure Water

Standard reference temperatures where ice melts at $0\,^\circ C$ and pure water boils at $100\,^\circ C$ at standard atmospheric pressure.

State Change Temperature Rule

While a substance is changing state, the temperature remains constant because energy is used to weaken or overcome intermolecular forces (potential energy) rather than changing kinetic energy.

Vaporisation

The process in which a liquid becomes a gas at its boiling point as additional thermal energy overcomes intermolecular forces.

Condensation

The process in which a gas turns back into a liquid as particles lose kinetic energy, move closer together, and can no longer overcome intermolecular forces of attraction.

Solidification

The process in which a liquid turns into a solid as particles lose kinetic energy until they can only vibrate about their fixed positions.

Evaporation

A change of state from liquid to gas that occurs at the surface of a liquid at any temperature when high-energy molecules escape.

Cooling Effect of Evaporation

The reduction in a liquid's temperature as the most energetic molecules escape, leaving behind molecules with lower average kinetic energy.

Factors increasing Evaporation Rate

Increases in temperature, larger surface area, and increased air movement (draughts).

Boiling vs. Evaporation

Boiling occurs throughout the liquid only at the boiling point, whereas evaporation occurs only from the surface at any temperature.