Objective: To learn about air currents and wind and how they relate to each other.
Standards: Structure of the Earth System (atmospheric composition and properties at different elevations; global circulation patterns and influence on local weather), Energy in the Earth System (heating of earth’s surface and atmosphere drives weather), and Properties and Changes in Matter (substance density).
Materials: talcum powder and unshaded lamp.
(1) While the lamp is turned off and cooled, sprinkle some talcum powder above it.
(2) Observe what happens.
(3) Light the lamp and let it warm up for a few minutes.
(4) When the lamp becomes hot, sprinkle more talcum powder above it (you may want to turn off the light to see the full effect).
(5) Observe what happens.
Science Behind It: When the lamp is heated, the powder rises up from the lamp because the bulb is producing heat and causing the air above it to rise and carry the powder with it. This represents convection, where the warmer air pushes upward because it is less dense and the molecules in the air are farther apart from each other. Before the lamp was hot, the talcum powder sank down along with the colder and denser air around the lamp. As the warm air rises, the cooler air flows in and sinks to occupy its place. Vertical movement of air is known as an air current, while horizontal movement of air on the same level is known as wind. The speed of air currents and wind is typically determined by the temperature difference between adjacent regions. The wind’s direction also depends on the location of these regions or areas.