What is the activity series of metals?

Can someone me with these questions plz.

If the density of water is 1.0 g/cm3, which of these materials would float in water, based on their densities? check all that apply. aluminum cork iron lead wax

1) which of the following is the best example of a physical change? a) sugar dissolving in tea b) firefly glowing 2) in the combustion of ethane, what is/are the reactants? c2h6 + o2 ==> co2 + h2o a) c2h6 and o2 b) co2 and c2h6