Answer the following :
(i) Why is the use of aspartame limited to cold foods and drinks ?
(ii) How do antiseptics differ from disinfectants ?
(iii) Why do soaps not work in hard water ?

Explanation

(i) Aspartime becomes unstable at cooking temperature . This is the reason why its use is limited to cold and drinks . Aspartame is a methyl ester fo the aspartic acid/phenylalanine dipeptide.
(ii) Antiseptics are antimicrobial substance that are applied to LIVING tissue/skin to reduce the possibility of infection, sepsis, or putrefaction.
(ii) Hard water is water that has positively charged calcium, magnesium and iron ions dissolved in it. Any solvent such as water can disssolve only so much of any substance . For instance , if we add salt to water, it will dissolve. Eventually, the water will reach a point where it can't dissolve more salt. Soap has negatively and positively charged ions. Both the negatively and positvely charged ions have to go into solution for the soap to dissolve.
Because hard water already has positively charged ions , it has less of a tendency to dissolve any more positively charged ions compared to water that is not hard. The positive ions in the soap can't go into solution very easily, so the soap doesn't dissolve as well as it would in normal water.