What are the properties of warm air?

Objective: To demonstrate the properties of air when it is warmed.

Standards: Structure of the Earth System (atmospheric composition and properties at different elevations), Energy in the Earth System (heating of Earth’s surface and atmosphere drives weather and ocean currents; convective circulation), Properties of Objects and Materials (object properties: temperature), Transfer of Energy (energy types, characteristics, and transfer properties; heat flows from warmer objects to cooler until equilibrium is reached), Structure and Properties of Matter (properties of gases), Light, Heat, Electricity, and Magnetism (ways to create heat – what is conduction?), and Conservation of Energy and Increase in Disorder (heat consists of random vibrations and motion of atoms and molecules).

Materials: a large, empty plastic pop bottle with its cap.

Procedure:

(1) Wet the cap of the pop bottle.

(2) Place the cap upside down on the top of the bottle.

(3) Lightly put your hands around the bottle.

(4) Hold the bottle but do not squeeze it.

Science Behind It: The cap will eventually “jump” or pop off of the bottle. This happens because when your hands are placed around the bottle, they cause the air inside the bottle to be warmed. As the air warms, the molecules of the air expand, and begin vibrating at a higher rate in an attempt to leave the bottle. The wet cap serves as a seal to the bottle at first, but eventually as the air becomes warmer and warmer, some of it will escape or vibrate against the cap so much that it causes the cap to “move” or fall off the bottle.

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