Answer:
A chemical reaction between Mg metal and oxygen that produced magnesium oxide (white powder).
Step-by-step explanation:
Solid magnesium (Mg metal) can react with
when it is lit. This produces magnesium oxide which is whitish in color. The balanced equation for the chemical reaction is shown below:
⇒

In the reaction above, Mg is the solid magnesium and MgO is the magnesium oxide which is a white powder.