Scaffolded notes
Build the idea
The surface heats unevenly
Sunlight reaches Earth by radiation. Dark soil, vegetation, pavement, water, and clouds absorb and reflect different amounts. Sun angle also varies by latitude, season, and time of day. These differences create temperature contrasts.
Warm air becomes less dense
Air touching a warm surface gains energy by conduction. Its particles move faster and spread out, lowering density. In surrounding cooler, denser air, the warmer parcel experiences an upward buoyant force. Cooler air moves in to replace it.
Convection transfers energy
The repeating movement of warmer fluid rising and cooler fluid sinking is convection. Atmospheric convection can produce local winds, build clouds, and redistribute thermal energy. The cycle continues while an energy difference remains.
Stop and explain
Check your thinking
1. Why is warmer air often less dense?
Possible response: Its particles move faster and spread farther apart.
2. What maintains a convection current?
Possible response: A temperature and density difference with continued energy transfer.
Interactive challenge
Try the science
Order the events in an atmospheric convection current.
- Warm air rises as cooler air moves in
- Air expands and becomes less dense
- Surface warms nearby air
- Surface absorbs solar energy
Before you leave
Exit ticket
Explain convection using energy, particle spacing, and density.