Heat and Temperature Quiz

Heat and Temperature

• Heat is the transfer of energy due to a temperature difference.
• Heat flows from hotter to colder objects.
• Temperature is the average kinetic energy of particles in a substance.
• The unit of heat is the Joule (J).
• Temperature is measured in Celsius (°C) or Kelvin (K).

Thermal Energy Transfer

• Conduction: Heat transfer by direct contact (e.g., a metal spoon in hot water).
• Convection: Heat transfer through the movement of fluids (liquids and gases). Warm fluids rise, cool fluids sink (e.g., boiling water).
• Radiation: Heat transfer via electromagnetic waves (e.g., the sun's heat reaching Earth).

Specific Heat Capacity

• Specific heat capacity is the heat required to raise the temperature of 1 kg of a substance by 1°C.
• Formula: Q = mcΔT
  • Q = heat energy (J)
  • m = mass (kg)
  • c = specific heat capacity (J/kg°C)
  • ΔT = change in temperature (°C)

States of Matter and Phase Changes

• Matter exists in three primary states: solid, liquid, and gas.
• Heat causes phase changes:
  • Melting: Solid to liquid (endothermic).
  • Freezing: Liquid to solid (exothermic).
  • Boiling: Liquid to gas (endothermic).
  • Condensation: Gas to liquid (exothermic).
• During phase changes, temperature does not change.

Latent Heat

• Latent heat is the energy required for a phase change without a temperature change.
• Latent heat of fusion: Energy to melt a solid.
• Latent heat of vaporization: Energy to boil a liquid.

Thermal Expansion

• Most materials expand when heated and contract when cooled.
• This is due to increased particle movement.
• The coefficient of expansion describes the material's expansion with temperature.

The Laws of Thermodynamics

• Zeroth Law: If two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
• First Law (Conservation of Energy): Energy cannot be created or destroyed, only transferred or transformed.
• Second Law: Heat naturally flows from hot to cold.
• Third Law: As temperature approaches absolute zero, entropy (disorder) approaches a minimum.

Applications

• Insulation: Materials with low thermal conductivity are used to reduce heat transfer (e.g., thermos, jackets).
• Engines and Refrigerators: Use thermodynamic principles to convert heat to work or move heat against its natural flow.

Exam Tips

• Understand the formulas.
• Be prepared to explain thermal processes (conduction, convection, radiation).
• Pay close attention to units, converting when necessary.