- Convection in gasses is the upward and downward movement of a heated gas.

- Convection is caused by differences in air densities, which are in turn caused by differences in temperature.

- Hotter air is less dense than cooler air, so it rises (see image blow).

- Convection causes objects to heat and cool unevenly, and is an important component of weather systems.

Mechanisms:

- Convection occurs when a portion of a gas becomes hotter than the surrounding gas, causing a difference in density.

- The hotter air rises and expands, displacing the surrounding cooler air, which then sinks.

- This cycle continues, transferring thermal energy from the bottom to the top of a fluid body, and is what we typically think of as convection.

- Convection is a crucial process in many environmental and industrial applications such as:

- Heating and Cooling of Buildings: Most homes use forced convection to distribute heated or cooled air throughout the house using forced-air systems (i.e. HVAC).

- Weather and Atmospheric Circulation: Weather and climate are in part driven by the convection currents in the atmosphere. When sunlight heats the Earth's surface, this heat is absorbed by the air near the surface causing the air to expand and become less dense, driving convection currents that affect weather.

- Oceanic Currents: The oceans also exhibit convection currents that help distribute heat and influence climate and weather patterns globally.

- Industrial Processes: Many industries use convection to transfer heat or cool materials, including:

- Metal Working: forging, casting, and heat treatment

- Food Processing: pasteurization, sterilization, and drying

- Chemical Manufacturing: distillation and crystallization