Ph Levels Lab

Activity 5-1b: Properties of acids and bases

Purpose:
To determine the acidity and pHevels of various substances using various pH indicators

Materials:

Equipment:

1. Eye dropper
2. Spot plate

Substances and indicators

1. Methyl orange
2. Indigo carmine
3. Bromothymol
4. Red litmus paper
5. Blue litmus paper
6. Magnesium ribbon
7. Substance A
8. Substance B
9. Substance C
10. Substance D

Procedure: 

See page 230 in the BC Science 10 textbook.

(But basically test Substance A through D using each of the pH indicators and record your results)

Observations

See the table below

Discussion

(Analyze questions are answered in conclusion)
Conclude and Apply
1)  a) A solution with pH 3 would have turned red in methyl orange, yellow in bromothymol blue, blue in indigo carmine and would not have changed colour in phenolpthalein. Litmus paper put in it would have turned red.
      b) A solution with pH 10 have turned yellow in methyl orange, blue in bromothymol blue, blue in indigo carmine and pink in phenolpthalein. Litmus paper put in it would have turned blue.
2) If I were to make a kit of pH indicators, I would pick litmus paper, phenolpthalein and methyl orange. This way, I would use a two step process with every substance I encountered. First, I would test the substance with litmus paper to determine if it was acid or base. If it was acidic, I would use the methyl orange, to determine whether it was mildly or acidic or strongly acidic. If the substance was basic, I would use the phenolpthalein to determine if it was strongly basic or mildly basic.
3) Lichen squished up and put in vinegar would be red.
4) Seawater tested with bromothyl blue would turn blue.
5) a) The areas of the oceans most affected by pH increase are the north Atlantic Ocean between North America and Europe, as well as between the lower tip of South America and Africa.
    b) The areas of the oceans least affected by pH increase are the Gulf of Mexico and Northern Australia.
 

 Conclusions

Guaging by the colours that each indicator turned, I can conclude that Substance A and C were acids, substance B was a base and substance D was neutral.The magnesium ribbon allowed me to verify which substances were acidic and which were basic because it is a metal. When a metal reacts with an acid, it releases hydrogen gas, which we can see in the form of bubbles in the substance, as I did in substance A and C. These bubbles were not, however, present in either B or D.  In order from most acidic to most basic, they were A, C, D, B. I know substance D was neutral because both the red litmus paper and the blue litmus paper which I dipped into it turned purple, right in between red and blue, which represent acid and base. In the Bromothymol blue, Indigo carmine and methyl orange, the indicators always put substance D in the middle range. I know that substance A was significantly more acidic than C, since A turned red in the methyl orange test, suggesting that it was under pH 4, while C did not turn red, suggesting it was over pH 4.

To have improved this experiment, I would also have tested the chemicals using phenolpthalein, in order to have more specific data and be able to narrow down the chemicals pH levels more specifically.