Red Cabbage pH Indicator Investigation

Good afternoon scientists! We had fun exploring pH today. Help your little one explore with this simple yet powerful investigation.

MaterialsRed Cabbage pH Indicator Investigation (2)

Red Cabbage (It looks purple)

Cutting Board and Knife (Adults Only)

Vinegar

Baking Soda and Spoon

At Least 3 Clear Containers or Cups (We used condiment containers)

Slotted Spoon

Large Pot (To Boil Cabbage)

Optional but recommended: Large Measuring Cup (Made it a lot easier to fill our containers with the cabbage juice)

Investigation

  1. Cut the bottom off the cabbage (You can regrow this if you choose, link coming soon). Cut the cabbage into at least four wedges. Place in a large pot with water and boil for 15-30 minutes.

2. Allow your cabbage to cool down in the pot, then remove the cabbage and set aside to eat later. Reserve all of the liquid. We let ours boil for about 30 minutes and it was very dark. I ended up adding some water to make our cabbage juice a little lighter purple color. Pour the cooled purple juice into the three clear containers about 3/4 of the way up.Red Cabbage pH Indicator Investigation (55) 3. Pour a spoonful of baking soda into one of the containers. Watch the reaction.Red Cabbage pH Indicator Investigation (48) 4. Pour Vinegar into one of the containers. Watch the reaction.Red Cabbage pH Indicator Investigation (58) 5. Read the talking points below and test other substances to find out if they are acids, bases, or neutral.

Talking Points

Acids have a pH of less then 7, and often have a sour taste. Neutral is 7. Bases have a pH higher then 7, and often have a bitter taste. 

A pH indicator is a substance that you can use to determine another substance’s pH. Red Cabbage juice is a low budget pH indicator, it can determine if a substance is an acid, base, or neutral. If a substance is an a acid the cabbage juice turns red. Vinegar is an acid. If the substance is neural the cabbage juice stays purple. If the substance is a base it turns the cabbage juice blue. The baking soda is a base.

If you have a pool then you might be familiar with pH strips they work in the same way as our indicator but give you more data then simply acid, base, or neutral. Litmus Paper is another example of a pH Indicator.

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