Lab: Household pH’s
Using a natural indicator and pH scale, your lab group will identify the pH of household substances and whether they are acidic, basic, or neutral.
Wear aprons as the indicator (cabbage juice) may stain!
Procedure:
1. Obtain 9 beakers (100 mL size). Pour 25 mL of the prepared natural indicator solution, cabbage juice (anthocyanin), into the beakers.
2. Make a row of white paper across the lab table and number it from 1 to 14, forming a pH scale.
3. To a beaker, use a dropper to add several drops of vinegar (CH3COOH) and swirl to mix. Place the beaker at the number 3 on the paper.
4. To a beaker, add a pinch of baking soda (NaHCO3), swirl to mix. Place the beaker at number 9 on the paper.
5. To a beaker, use a dropper to add several drops of ammonia (NH3), swirl to mix. Place the beaker at number 11 on the paper.
6. You should refer to these colored solutions as reference points to identify the pH of the following solutions.
7. To a beaker, use a dropper to add several drops of shampoo. Swirl or stir to mix. Observe the color change that occurs. Record your observations in the table attached. Place it on your pH scale where you think the color belongs according to the reference solutions. Label the beaker with the name of the substance added.
8. Repeat step 7 with each substance (laundry detergent, milk of magnesia, mouthwash, carbonated beverage, and dish soap) and the remaining beakers.
9. When all the substances have been added and placed along the pH scale, record their pH’s in the table and placements on the pH scale below.
3 9 11
Data Collection:
|
Substance |
Color |
Approximate pH |
|
Cabbage Juice, anthocyanin indicator |
|
|
|
Vinegar (CH3COOH) |
|
|
|
Ammonia (NH3) |
|
|
|
Baking Soda (NaHCO3) |
|
|
|
Shampoo |
|
|
|
Dish Soap |
|
|
|
Laundry Detergent |
|
|
|
Mouthwash |
|
|
|
Milk of Magnesia |
|
|
|
Carbonated Beverage |
|
|
Analysis and Conclusions:
1. Which substances are acids?
2. Which substances are bases?
3. A flowering plant, hydrangea, has flowers that contain anthocyanin. A single plant may produce flowers that are pink, purple, or blue, depending on pH levels of its environment. What conditions do you think may cause the production of pink flowers?