Heat and Temperature Concepts

Heat and Temperature

• Heat is kinetic energy; faster particle movement equals higher heat.
• Temperature is the average kinetic energy of particles in a system, measured in Celsius, Kelvin, or Fahrenheit.
• Water's freezing point (Celsius 0°C, Kelvin 273.15°K, Fahrenheit 32°F) and boiling point (Celsius 100°C, Kelvin 373.15°K, Fahrenheit 212°F) are key temperature references.
• Absolute zero (no particle motion) is -273.15°C, 0°K, -459.67°F.
• Heat transfer occurs from hotter to colder areas, through conduction, convection, or radiation.
• Cold is the absence of heat, not a substance.

Heat Transfer Mechanisms

• Conduction: Direct contact transfer of heat between objects, until thermal equilibrium is reached. (e.g., metal rod in a fire).
• Convection: Heat transfer via movement of matter (liquids or gases), driven by density differences caused by thermal expansion. (e.g., boiling water).
• Radiation: Heat transfer as electromagnetic radiation. (e.g., heat from a fire).

Heat and Energy Transformations

• Heat is a form of energy and can be transformed from/to other types, e.g., chemical to heat, kinetic energy to heat, electromagnetic radiation to heat.
• Heat engines, like car engines, transform heat energy into mechanical work.

Laws of Thermodynamics

• First Law: Energy (heat) in an isolated system remains constant. It can change form but not be created or destroyed.
• Second Law: Heat cannot spontaneously move from a colder to hotter object. Entropy (disorder) increases in isolated systems over time, moving toward thermal equilibrium.
• Third Law: As entropy approaches a constant value, a system's temperature approaches absolute zero. This theoretical limit is never actually achieved.

Heat Properties

• Specific Heat: The amount of energy needed to raise the temperature of a unit of mass by 1 degree Celsius. Different substances have different specific heats.
• Thermal Expansion: Materials expand as they heat, and contract as they cool.
• Latent Heat: The energy absorbed or released by a substance during a phase change (solid to liquid, liquid to gas, etc.) without a change in temperature.

Heat Engines

• Heat engines convert heat energy into mechanical energy, such as those in cars and other machines.