Important of each part of Bunsen burners

chimney helps to allow the air and gas to mix before they burn at top

collar helps to allow to open and close the air hole

air tube helps to allow air to enter in the Bunsen burner

jet helps to allow the gas to rush out from the gas supply

base helps to support the Bunsen burner

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.