Name: _____________________
Period:______
Date:______
ACID BASE LAB
Introduction
Acids are materials that have certain properties in common. Bases (also called alkalis) are other substances with
a different set of properties. The most striking property of both acids and bases is their ability to change the
color of certain vegetable materials. A common vegetable whose color responds to acids and bases is red
cabbage.
The acidity of a solution can be expressed using the pH scale. Acidic solutions have pH values less than 7,
basic solutions have pH values greater than 7, and neutral solutions have a pH value equal to 7.
In this experiment, you will investigate some of these properties with materials that are found around your
home. In addition, you will learn how chemists use the pH scale to identify acids and bases.
A pH indicator is a substance that has a different color when added to acid or base. In this experiment a pH
indicator is made from red cabbage.
PROCEDURE
CAUTION: Do not eat or drink in the laboratory!
1. Line up the 7 test tubes in a test tube rack so that they can hold solutions from # 1 – 7 as shown in the data
chart. This helps to remember which solution is in which test tube and avoid a mixup.
2. Measure about 1 mL of each of the 7 solutions into the 7 lined up test tubes. (1 mL  width of your pinky
finger
Part 1 – Litmus Paper
3. Obtain a strips each of blue and red litmus paper for each of the 7 solutions. In all you will need 7 blue
litmus papers and 7 red litmus papers.
4.
Place these strips on a small piece of paper towel and use a stirring rod to transfer one drop of solution # 1
to the blue litmus paper and one drop to the red litmus paper. Record the color of each dot in the data table.
5. Wash and dry the stirring rod.
6. Repeat step 3 with the remaining solutions. Be sure to clean and dry the stirring rod after each solution.
Part 2 – Red Cabbage Juice Indicator
7. After completing Part 1, add about 1 mL of red cabbage juice indicator to each of the 7 test tubes using the
pipette provided. Record the color of each solution in the data table by comparing with the chart below.
Highly Acidic
approximate pH:
2
color of extract:
red
Neutral
4
6
8
10
Highly basic
12
purple
violet
blue
blue-green
Green
8. Clean up your lab station. Wash the test tube contents down the sink with plenty of water. Rinse the test
tubes with tap water. Do one final rinse with distilled water and allow them to drain in the test tube rack.
Discard litmus paper and paper towels in the trash.
OBSERVATIONS
Test
Solution
Tube
1
vinegar
2
ammonia
3
lemon juice
4
Club soda
5
baking soda
solution
6
antacid
7
Ivory soap
Blue Litmus
Red Litmus
Red Cabbage
Juice
pH
CONCLUSIONS Questions
1) Is there a pattern in how the litmus paper changes color? Yes/No
_______ turn red litmus blue and ________ turn blue litmus red. ( ACID/BASE)
2) What color is the cabbage indicator when neutral?
3) What color is the cabbage indicator with a base?
4) What color is the cabbage indicator with an acid?
5) Describe how the color of the red cabbage juice indicator changes as you move from highly acidic to highly
basic solutions.
6) Which of the household solutions are acids? How did you determine this?
7) Which of the household solutions are bases? How did you determine this?
8) Discuss the advantages and disadvantages of litmus paper and red cabbage juice. Which indicator do you
think is better? WHY?