Which of these is evidence that an unbalanced force is acting on an object? The motion of the object is changing

The mass of the object is changing.

The object continues moving in a straight line

The object remains at rest.

The motion of the object is changing

Explanation:

Objects will only change their motion (direction, speed) if there is an unbalanced force of some kind acting on them. Balanced forces result in no change in the object's state of motion.

Magnesium and Hydrochloric acid or Mg and HCl.

The reactants in a reaction are the elements or compounds doing the actual reacting. In this word problem, you can identify this with the keyword reacts. It states, "Magnesium reacts with hydrochloric acid." Thus, you can also infer that the products are what are produced.

Hope this helps!