Sound, Energy & Heat Transfer

• Describe the difference between heat and temperature.

• Know that energy is conserved, meaning it cannot be created or destroyed, only transferred or changed from one form to another.

• Know that thermal energy will always transfer from hotter regions or objects to colder ones

• Describe how some energy including heat is dissipated and becomes less useful during energy transfer

• Describe thermal transfer by the processes of conduction, convection and radiation.

• Explain cooling by evaporation.

• Describe sound waves as the vibration of particles

• Draw and interpret a waveform’s amplitude, wavelength, peak, trough, frequency

• Link loudness and amplitude, pitch and frequency.

• Use waveforms to show how sound waves interact to reinforce or cancel each other.

Heat vs Temperature

• Heat: A form of energy transfer that moves between objects due to a difference in temperature. Measured in joules (J). It depends on the material, mass, and temperature difference.

• Temperature: A measure of the average kinetic energy of particles in a substance. Measured in degrees Celsius (°C) or Kelvin (K).

  
  🔑 Key difference: Heat is energy in transit, while temperature is a measure of how hot/cold something is.

Conservation of Energy

• Energy cannot be created or destroyed, only transferred or transformed.

• Example: In a kettle, electrical energy → thermal energy → some dissipated as sound and heat to surroundings.

Thermal Energy Transfer Direction

• Heat always flows from hotter → colder objects or regions, until thermal equilibrium is reached.

• Example: A hot cup of tea cools because heat transfers into the colder air.

Dissipation of Energy

• Some energy becomes spread out into the surroundings and is less useful (often as wasted heat, sound, or light).

• Example: Car engine → kinetic energy → but some lost as heat, friction, and noise.

Thermal Transfer Processes

1. Conduction (solids, especially metals):

   • Particles vibrate and pass on energy to neighbours.

   • Metals are good conductors (free electrons transfer energy quickly).

   • Insulators (wood, plastic) are poor conductors.

2. Convection (liquids & gases):

   • Warm, less dense fluid rises; cooler, denser fluid sinks → convection currents.

   • Explains heating in a room or boiling water.

3. Radiation (no medium needed):

   • Heat transfer by infrared waves.

   • Can travel through a vacuum (e.g., Sun’s heat reaching Earth).

   • Dark, matte surfaces absorb well; shiny, light surfaces reflect.

Cooling by Evaporation

• Fast-moving molecules at the surface escape into the air as gas.

• The average kinetic energy of remaining particles decreases → temperature drops.

• Example: Sweat evaporating cools the body.

Sound Waves

• Sound is a longitudinal wave caused by vibrations of particles in a medium (solid, liquid, gas).

• Requires a medium → cannot travel in a vacuum.

Waveform Features

• Amplitude: Maximum displacement (height of wave) → linked to loudness.

• Wavelength (λ): Distance between two peaks or troughs.

• Frequency (f): Number of waves per second (Hz) → linked to pitch.

• Peak: Top of wave.

• Trough: Bottom of wave.

Loudness & Pitch

• Loudness ↔ Amplitude: Larger amplitude = louder sound.

• Pitch ↔ Frequency: Higher frequency = higher pitch.

Wave Interference

• Constructive Interference (reinforcement): Waves meet in phase (peaks align with peaks, troughs with troughs) → larger amplitude.

• Destructive Interference (cancellation): Waves meet out of phase (peak + trough) → reduce or cancel sound.

• Example: Noise-cancelling headphones use destructive interference.