University of Virginia
Physics Department

Flower Indicators

A Physical Science Activity

Student Activity

Materials (for each lab group)

 

Procedure

  1. Prepare a table like the one shown below.
  2. Using a mortar and pestle, crush the petals of one of the flowers.
  3. Add 8 ml of alcohol to the mortal and continue to crush the flower petals.
  4. Use the medicine dropper to transfer one ml of the alcohol and crushed petal solution into a single well.  Continue adding the solution to six separate wells lined up vertically.
  5. Thoroughly rinse the mortar and pestle with tap water.
  6. Repeat steps 1-5 with each type of flower.
  7. Use a dropper to add one ml of  HCl to each of the wells in line #1.
  8. Use a dropper to add one ml of  vinegar to each of the wells in line #2.
  9. Use a dropper to add one ml of distilled water to each of the wells in line #3.
  10. Use a dropper to add one ml of ammonium hydroxide to each of the wells in line #4.
  11. Use a dropper to add one ml of sodium hydroxide to each of the wells in line #5.
  12. Use a dropper to add one ml of unknown acid or base to each of the wells in line #6.
  13. Draw a diagram showing the color change after adding the acid and base solutions.
  14. Determine relative pH of the unknown solution.
A
B
C
D
E
HCl
Vinegar
Distilled Water
NH4OH
NaOH
Unknown Solution

 

Flower Key:

  1. _________________
  2. _________________
  3. _________________
  4. _________________
  5. _________________

 

Extensions

Try making an indicator from boiled cabbage and compare it to the flower indicators you have already made.

 

Assessment

  1. What is the relative pH of the unknown solution?



  2. Which flowers made the best indicators?  Explain why.



  3. Could two flowers of different colors be used to indicate the same pH?  Explain your answer.