testing for acidity and alkalinity (chem lab)

Acidic vs. Alkaline
Introduction: Potential of hydrogen, or pH, is a scale used to express the acidity or alkalinity of a solution. The scale ranges from 0 to 14, below seven represents acidity, seven is neutral, and more than seven is basic. Acid-base indicators show whether the solution is acidic or alkaline. They do this by reacting with the solution, seen as a color change, as the concentration of hydrogen (H+) or hydroxide (OH-) ions changes in an aqueous solution. Different indicators change different colors depending on what they are mixed with and the acidity or alkalinity of that solution. In the Reference Tables for Physical Setting/CHEMISTRY, table M shows the name of the indicator, the approximate pH range color, and different color change possibilities.

Materials:
1. Depression plate
2. Sharpie marker
3. Dropper bottles: 1M hydrochloric acid, 1M sodium hydroxide, ammonia, vinegar, distilled water
4. pH indicator dropper bottles: bromothymol blue, red litmus paper, methyl orange, phenolphthalein
Procedure:
1. Number the wells in the depression plate form 1-6 with the sharpie.
2. Into each well on the depression plate, add 10 drops of the following substances:
a. Well 1: 1M hydrochloric acid
b. Well 2: 1M sodium hydroxide
c. Well 3: distilled water
d. Well 4: milk
e. Well 5: vinegar
f. Well 6: ammonia
3. Test each well with bromothymol blue. Record the color each well turned.
4. Rinse out the depression plate in the sink and then with distilled water from a wash bottle.
5. Repeat steps 2-4 with each different indicator.
Results: (results may vary based on the concentration of the indicators)
Substance
Bromothymol blue
Red litmus paper
Methyl orange
Phenolphthalein
pH range
1M hydrochloric acid
Yellow
Red
Red
Clear
Less than 3.1
1M sodium hydroxide
Blue
Blue
Yellow
Pink
More than 9
Distilled water
Yellow
Red
Red
Clear
Less than 3.1
Milk
Yellow
Purple
Yellow
Clear
4.5 - 6.0
Vinegar