If an atom gains an electron it is known as what ? and has a negative charge

If an atom gains an electron and gets a negative charge because of it, it is a negatively charge ion AKA an anion.

False, as a substance changes from a solid to a liquid and from a liquid to a gas the molecules get farther apart from each other

You would be correct, boiling water does disinfect contamination.    the property of disinfecting means to kill  germs, bacteria and other pathogens or contamination  that might cause an infection or cause a person to become sickly. a couple methods of disinfecting are using soap, other cleaning supplies or by simply "boiling" the contaminate.  the reason why boiling water disinfects certain attributes is because some cells cannot survive the heat and pressure.