When methanol is burned and leaves a residue is this a chemical or pyhsical change?
When methanol burns completely it should not leave any residue.
There are two possible explanations for a residue:
The methanol was contaminated with a substance that won't burn. In this case there is a physical change: a mixture was separated by burning off one of the compounds, i.e. tha methanol.
The burning was not complete by lack of oxygen. In that case the burning reaction would be like (no coefficients):
And the carbon would be the residue. This is a chemical change.