Is the dissolution of sodium chloride in water a physical or chemical change?
It is a physical change. When the NaCl dissolves, the Na and Cl ions do break apart. It is not a chemical change because no new chemical bonds are formed. It can also be considered a change of state.
NaCl(s) -> NaCl(aq)
It is a very common misconception that this process is a chemical change. According to data from AAAS 21% of high school students believe that dissolving is a chemical change. I know an AP Chem teacher who teaches that it is a chemical change, I've tried to explain to him why it is a physical change to no avail. :(
You can see info about this misconception and others at the following website under the topic "Many substances react chemically in predictable ways..."