Why can't chemical changes be undone? Because of the chemical properties. Because Mark is an idiot. Because they need energy. Because new substances are formed.

Because new substances are formed.

Explanation: A chemical property is any of a material's properties that becomes evident during, or after, a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity.  Once a chemical change occurs it cannot be undone due to the change in chemical identity.  The creation of a new substance is not reversible.  

the answer is yes

it has kinetic energy

reason

an object has kinetic energy when you stop the force carrying it, the object will stay in motion.

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