Cabbage Juice Lab

Purpose:To test the pH of different solutions

using cabbage juice.

Why use cabbage juice?

• By boiling the red cabbage leaves, we extracted a class of pigment molecules called anthocyanins into solution. Anthocyanin molecules will change their color depending upon the pH of their environment and can indicate the pH of a solution.

What is pH?

• The pH scale measures how acidic or basic a substance is.

• It ranges from 0 to 14. • A pH of 7 is neutral. • A pH less than 7 is

acidic, and a pH greater than 7 is basic.

What should SOIL pH be to help plant growth?

Most soils for plant growth should be around 6 to 7 (slightly acidic to neutral) for optimal growth. If it is too acidic, lime can be added to raise the pH level.

If the pH of the soil is too acidic, this may slow down the decomposition process of bacteria.

Investigation

• Identify each solution as either an acid, base, or neutral.

Procedure1. Read first page of Acid and Bases Lab Report2. Answer Pre-Lab Questions– Circle your prediction of each substance; acid, neutral or

base3. Obtain a watch glass, eye dropper and a 50 mL beaker of

cabbage juice4. Place a small amount of the household substances being tested

on watch plate slowly add cabbage juice with eye dropper5. Record color change and pH for each household substance in

chart on page 3 of your lab report6. Be sure to wash off and dry your watch plates between tests7. Complete lab report including all charts and concept questions8. Clean lab materials and return them to the back of the room

Hand Sanitizer

Hand Sanitizer

pH: 7 (neutral)

Lemon Juice

Lemon Juice

pH: 2-3 (acid)

Apple Juice

Apple Juice

pH: 3 (acid)

Vinegar

Vinegar

pH: 3-4 (acid)

Baking Soda

Baking Soda

pH: 8-9 (base)

Shampoo

Shampoo

pH: 5.5 (acid)

Conditioner

Conditioner

pH: 7 or 8(base)

Antacid

Antacid

pH: 9 or 10(base)