How to Make pH Strips

Learning about acids and bases is a fun project for kids to do at home or at school. Chemistry becomes magic when kids can make a piece of paper change color, and with inexpensive homemade pH strips, they can test everything in the house. These pH strips are made with red cabbage, so they're even safe for kids to test on their tongues.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Distilled or bottled water
• Red cabbage
• Blender
• Saucepan
• Paper coffee filters
• Scissors
• Toothpick

1. Boil 1 cup distilled or bottled water in a saucepan.

2. Chop the red cabbage into small enough pieces to fit into the blender.

3. Add just enough water to make the cabbage blend easily. Don't add too much water or the colored solution will be too weak to work well.

4. Blend the cabbage and dump it into the boiling water. Remove the pan from the heat, and allow it to sit until it's cool enough to touch.

5. Use a coffee filter to strain the cabbage from the water. Discard the cabbage.

6. Soak some coffee filters in the cabbage water until they're completely and deeply colored. Set the filters out to dry on a ceramic or metal surface that won't absorb the dye and stain.

7. When the coffee filters are dry, cut them into strips.

8. Use the strips to test pH either by dipping them into a liquid, or by dipping a toothpick into a liquid and smearing it on the strip. Acids will make the strip turn red and bases will turn it blue or green. If the strip doesn't change color, it is pH neutral.

Tips & Warnings

• Soak a piece of drawing paper in the cabbage water. When it's dry, use a toothpick dipped in an acidic or basic material (such as vinegar or soap) to write or draw on the paper. Use metal tongs to dip the coffee filters into the cabbage water if you don't want to dye your fingers.

Resources

• Acids and Bases Science Project Ideas
• Image of Red Cabbage pH scale