Glossary
Conduction
Heat transfer through direct physical contact between objects or within a material, primarily via molecular collisions. It is most efficient in solids.
Example:
Holding a metal skewer over a campfire causes the end in your hand to get hot due to conduction along the metal.
Convection
Heat transfer through the movement of fluids (liquids or gases) caused by density differences. Warmer, less dense fluid rises, while cooler, denser fluid sinks, creating currents.
Example:
The circulation of air in a room heated by a radiator, where warm air rises and cool air sinks, is an example of convection.
Electromagnetic Waves
Waves that consist of oscillating electric and magnetic fields, capable of transferring energy through a vacuum, which is the mechanism for heat transfer by radiation.
Example:
The warmth you feel from the sun on your skin is carried by electromagnetic waves traveling through the vacuum of space.
Fluid Movement
The bulk motion of liquids or gases driven by density differences, which is the underlying mechanism for heat transfer by convection.
Example:
The rising and falling of water in a boiling pot, creating a rolling boil, is a clear demonstration of fluid movement facilitating heat transfer.
Heat
The transfer of thermal energy between objects or systems due to a temperature difference. It always flows from a warmer area to a cooler area.
Example:
When you place a cold spoon into a hot cup of coffee, heat transfers from the coffee to the spoon, warming the spoon.
Molecular Collisions
The primary mechanism by which kinetic energy is transferred between particles in direct contact, leading to heat transfer via conduction.
Example:
When a hot iron is placed on a cold shirt, the rapid molecular collisions at their interface quickly transfer energy, warming the fabric.
Radiation
Heat transfer through electromagnetic waves, which does not require a medium and can travel through a vacuum. All objects emit and absorb thermal radiation.
Example:
Feeling the warmth of a bonfire from a distance, even without touching it, is due to radiation.
Specific Heat
The amount of heat energy required to raise the temperature of one kilogram of a substance by one degree Celsius (or Kelvin). It is a material property.
Example:
Water has a high specific heat, which is why it takes a lot of energy to boil and why it's used in car cooling systems to absorb excess heat.
System
A defined region or collection of matter being studied, whose energy changes are tracked, often in relation to its surroundings.
Example:
In a calorimetry experiment, the water and the object placed within it together form the system for which heat exchange is calculated.
Temperature Difference
The variation in temperature between two objects or regions, which is the driving force for heat transfer. Heat always flows from higher to lower temperature.
Example:
A significant temperature difference between the inside and outside of a house on a cold day causes heat to escape through the walls and windows.
Thermal Energy
The total internal energy of a system, including the kinetic and potential energy of its particles. Heat is the transfer of this energy.
Example:
A large iceberg contains a vast amount of thermal energy even though its temperature is low, due to the sheer number of water molecules it contains.
Thermal Equilibrium
The state where two or more objects in contact have reached the same temperature, and there is no net transfer of heat between them.
Example:
When a cold drink is left out on a warm day, it eventually reaches thermal equilibrium with the surrounding air, becoming room temperature.