A chemical change affects on the molecular level of matter, which makes it irreversible. Combustion is a pretty good exmple. Physical changes are reversible and dont alter the formula. Hope this helped!
B. Magnesium + Hydrogen Sulfide (Reactors) ----> Magnesium Sulfide + Hydrogen (Products)
Magnesium dichloride or Magnesium chloride
If I remember correctly, the answer is <span>Friction force.</span>
