Chemistry › Acids and bases › pH scale and other indicators

Age level:  11-13

Questions

1. The pH of a creek in an industrial area was monitored by a class of students over a period of 4 weeks. The following data was obtained:

   Day	1	4	7	10	13	16	19	22	25	28
   pH	7.4	7.3	7.3	7.4	7.2	5.1	3.9	4.0	6.5	7.2

    

   a Plot this data on a graph.
   b A local factory had released acid into the creek accidentally.
      i During what period was this?
     ii Local authorities took action when they learnt of the spill. What do you suggest the authorities did? On what day did this happen?

   
   
   

2. a What is the function of an indicator?
   b In what situation would it be preferable to use:
       i litmus paper instead of universal indicator?
      ii universal indicator instead of litmus paper?

   
   
   

3. a Suggest why lemon juice tastes sourer than orange juice.
   b What would you expect the pH of grapefruit juice to be?

   
   
   

Answers