Year 9 Science: Energy, Heat, and Waves Revision

Practice vocabulary flashcards for the Year 9 Science revision test covering the conservation of energy, energy transformations, efficiency, sound wave propagation, and heat transfer mechanisms.

Law of Conservation of Energy

A fundamental scientific law stating that energy cannot be created or destroyed, but can only be transferred between objects or transformed from one form to another.

Vacuum

A space devoid of matter, such as outer space, through which sound waves cannot travel because there are no particles present to transmit mechanical vibrations.

Speed of Sound

The rate at which sound waves propagate through a medium, which travels slowest in colder gases (such as air at $0^\circ\text{C}$), faster in warmer gases (air at $20^\circ\text{C}$), faster in liquids (water at $20^\circ\text{C}$), and fastest in solids (glass at $0^\circ\text{C}$).

Waste Energy

Energy produced during an energy transformation or transfer that is not utilized for the system's intended useful output, such as the sound energy produced when bouncing a basketball.

Kinetic Energy

The energy possessed by an object due to its motion, which depends on both its speed and mass; for example, a bus travelling at $100\,\text{km/h}$ has significantly more kinetic energy than a car or motorcycle travelling at the same speed due to its larger mass.

Solar Panel

An invention designed to capture sunlight (radiant energy) and convert it directly into electrical energy.

Chemical Potential Energy

A form of potential energy stored within the chemical bonds of substances such as petrol or food, which is released when these substances undergo chemical reactions.

Energy Efficiency

The percentage of total input energy converted into useful energy output by a system, calculated as $\left(\frac{\text{Useful Energy Output}}{\text{Total Energy Input}}\right) \times 100\%$.

Elastic Potential Energy

Energy stored in an elastic object as a result of deformation or stretching, such as the energy held in a drawn bowstring before being transferred into the kinetic energy of an arrow.

Sankey Diagram

A specialized flow diagram that visualizes the distribution of energy in a system, using proportional arrow widths to represent total input energy, useful output energy, and waste energy.

Longitudinal Wave

A type of wave, characteristic of sound, in which the particles of the transmitting medium vibrate back and forth parallel to the direction in which the wave is traveling.

Compression and Rarefaction

The alternating regions of a longitudinal sound wave: compressions (indicated by the bottom pointer) are areas where particles are pushed tightly together at higher pressure, while rarefactions (indicated by the top pointer) are areas where particles are spread apart at lower pressure.

Thermal Conduction

The transfer of heat through direct particle-to-particle contact within a solid, occurring significantly faster through good conductors like aluminium compared to poor conductors like glass.

Thermal Conductor

A material that easily and rapidly transmits heat through itself; for example, metals are good conductors that quickly transfer thermal energy to the skin on hot days, whereas insulators like wood do not.

Convection

The transfer of heat in fluids (liquids and gases) through bulk particle movement, such as when warmer, less dense air at $30^\circ\text{C}$ from outdoors flows into an air-conditioned room at $18^\circ\text{C}$.