An experiment is performed on a puck on a level air hockey table, where friction is negligible. a constant horizontal force is applied to the puck, and the puck's acceleration is measured. now the same puck is transported far into outer space, where both friction and gravity are negligible. the same constant force is applied to the puck (through a spring scale that stretches the same amount), and the puck's acceleration (relative to the distant stars) is measured. what is the puck's acceleration in outer space?

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.