In the SI system the unit of heat is the joule. The calorie was defined so that the heat capacity of water was equal to one.The heat capacity of a substance is the amount of heat required to raise the temperature of a defined amount of pure substances by one degree.
Number #3 is Endothermic
Why? I can't explain. I Just left class where they were just explaining that.
The population will continue to grow but as we grow so does pollution. Some would need vaccines to cure simple diseases like the flu but what if there would not be enough?