When you drop things into bodies of water, some things sink and some things float. What determines this?

how dense the object is and if it has air in it.

Explanation:

Density determines the situation.

The denser the body than water, it sinks in water

The less dense the body than water, it floats on water.

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.