Why is the law of gravity an example of a universal law?
gravity exists for masses in a closed system only
o gravity exists only on the earth and moon.
gravity exists between small masses in an open system only.
gravity exists between any two masses in the universe.
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wher is the rest of the question

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.