Warm air rising at the equator and cold air sinking at the poles is an example of…

atmospheric circulation

Explanation:

Atmospheric circulation occurs  because the Sun heats the Earth more at the equator than at the poles.

Warm air is known to rise at the tropics which lies closer to the equator and moves towards the poles. Atmospheric circulation is driven by the rotation of the earth.

The air cools and flows back towards the Equator to be warmed up again. A sort of convection current is thereby set up.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.