Why is chemistry a science but alchemy was not?

What are the resulting coefficients when you balance the chemical equation for the combustion of ethane, c2h6? in this reaction, ethane is burned in the presence of oxygen (o2) to form carbon dioxide (co2) and water (h2o). (g)+(g)→(g)+(g)

Compare and contrast physical changes with chemical changes.

Asubstance is a good conductor of electricity which of the following best explains a probable position of the substance in a periodic table