Describe how detergents (e. g. washing powder) are able to remove greasy stains from our clothes.
The water in Gothenburg is "soft". What is meant by soft water and why do we need
to use less detergent in soft water areas and more detergent in hard water areas.

a polar bond is formed when electrons are shared unevenly between atoms

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.