Page 12 - ..Science E-book Prim.6 2024-2025 1st term part2_Neat - Copy
P. 12
Convection: the transferring of
thermal energy through liquid or
gas by the movement of
molecules.
“Hot molecules, less density,
rise up”
“Cold molecules, high density
fall down”
Thermal energy transfers through the space to
the earth’s atmosphere by radiation
It also transfers through the atmosphere by
convection as convection current.
By heating liquid or gas, it expands
(molecules far away) and become
low in density so it rises up.
By cooling liquid or gas, it contracts
(molecules close) and become high in density so
it falls down and replace the warm molecules.
Hot molecules move up and cold
molecules move down.
This movement occurs by the help of gravity and form a cycle of
convection currents.
This movement of air molecules leads to formation of wind.
Convection current in the atmosphere helps in:
1- Water vapor movement.
2- Formation of wind and ocean currents.
3- Determining the regional climate.
10
Second Term
