Instructables
Picture of Testing the Water



Observation: When I was rinsing out my bowl of red cabbage soup the water turned green.


 
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Step 1: Hypothesis: I believe the cabbage in the cabbage soup changes color to green when it comes in contact with certain other substances. I also believe there must have been traces of one of these substances in my water.

Picture of Hypothesis: I believe the cabbage in the cabbage soup changes color to green when it comes in contact with certain other substances. I also believe there must have been traces of one of these substances in my water.

Step 2: Supplies:

Picture of Supplies:

you will need:
- 9 plastic cups
- a red cabbage
- a pot
- distilled water
- paper towls
- gloves
- a plastic spoon
- a dropper
Test Items:
-distilled water
-tap water
- vinegar
- bleach
- salt
- baking soda
- soap
- a clear soft drink

Step 3: Step 1. Preparing for Soup:

Picture of Step 1. Preparing for Soup:

Important note: Be sure to use DISTILLED WATER not tap water.

I gently wiped out the pot with a dry towel. I poured some distilled water into the pot and made circular motion with the pot to clean it. I dumped it and repeated the water step once more to ensure that nothing was left behind. It is not necessary to rinse the red cabbage.

Step 4: Step 2. Making The Soup:

Picture of Step 2. Making The Soup:
temp_1860490422.jpg

I added a cup and a half of distilled water to the pot. I heated it to just barely boiling. Next I added about three leaves and cooked them for three to five minutes until they lose their color. Look at the picture that compares faded to fresh. Then I fished them out and added more leaves. I repeated this until I had used about ten full leaves.

Notes: I made a small batch of soup. It might be a good idea to make more soup depending on the size of the cups you intend to use.

Step 5: Step 3. Preparing To Mix:

Picture of Step 3. Preparing To Mix:

I started by lining up the test items on a table in no partcular order. I placed a layer of paper towels across the table in front of the test items and lined up one cup across from each item. I wrote the corresponding abbreviation on it. Example: On the one across from the vinegar I wrote, vin. Then I filled each cup with an equal amount of soup.

broregret8 months ago

i suggest using less baking soda in your cabbage soup next time you cook. ;-)

awesomechik8 months ago
we do this as a science experiment with kids: put a few cabbage leaves in a microwave safe bowl and nuke for a couple of minutes until juice starts appearing in the dish; fry an egg in the cabbage juice to get a green egg, serve with ham!
dropkick8 months ago

The stock that comes from cooking a red cabbage can be used to tell if other substances are acidic or alkaline/base. When I was a kid I used to make litmus paper by soaking a neutral white paper in in red cabbage stock and then drying it.

My greatest memory of using it was when I used it to check the volcanic dust that had settled over everything after Mt. Saint Helens blew. The news kept saying it might be acidic and not to wash it off. I found that it was slightly alkaline. We washed off the cars and house.

yoda333 (author)  dropkick8 months ago
Thats really cool
Nostraquedeo8 months ago

That was a very good demonstration of the scientific process.

yoda333 (author)  Nostraquedeo8 months ago
Thak you
hammer98768 months ago

I wish I had you as a chemistry teacher.

shadowjfaith8 months ago

Tap water is often treated with bleach as well as chlorine during the sanitation process.

The chlorine in water supplies is typically in the form of chloramine. It is more stable and takes longer to off-gas.

yoda333 (author)  shadowjfaith8 months ago
That makes sense. Thanks for sharing!

Here's some information if your interested regarding the disinfection process dealing with chlorine and it's off shoots

http://water.epa.gov/drink/contaminants/basicinfor...

nanaverm8 months ago

Commercial vinegars (like Heinz distilled white vinegar) are changed to have 5% acidity. But an interesting experiment!

owlsquest8 months ago

I do this as an entry acid/base lab for Grade 10 students, but solution is not boiled. I put half a head of red cabbage, cut up in chunks into a blender and then add one cup of distilled water. Blend to a puree and strain the liquid off. We use round filter paper at school and soak it in the liquid for up to 10 minutes and then hang the filter paper in the fume hood to dry. I have also done this with my nephews and nieces using coffee filters and then hanging them to dry outside. Gets fairly smelly so I recommend the outdoor hanging. Once dry, filters can be either stored in Ziploc bags in the freezer or used right away. Students (or my kids) fold the paper in half, half again and then half again twice more -- makes 8 pie wedges. Label the circular edge with whatever substance you are testing the pH for, grab some droppers (have used plastic spoons in a pinch) and start adding your testers. Cheap way to introduce acid /base.

omnibot8 months ago
Nice experiment. I've come across cabbage as a PH indicator in old chemistry books but never tried it myself. I think salt is considered not to have a PH which is why it wouldn't change the colour.
yoda333 (author)  omnibot8 months ago
It would make sense that salt doesn't have a PH. Thanks for pointing this out.

pH is actually a measure of the activity of a hydrogen ion, and salts do have an effect on this.

On the spit and saliva front, they as substances tend to be near enough neutral which shows green on the pH scale(this is of course affected by what you eat and drink so not always).
yoda333 (author)  ClockworkPheonix8 months ago
Good to know.
jmwells8 months ago
Salt is neutral Ph. What you found is the original litmus test. Good work. Be sure to wash the cabbage if you eat it.
yoda333 (author)  jmwells8 months ago
I'll take your word on salt being a neutral. It was very hard to tell salt and the two water samples. Even though I labled salt as a base it was almost exactly the same as the distlled water. Thanks for posting!
GinaT8 months ago
well done! i have an 8 yr old that is developing an interest in science and i am going to do this with her this weeks
yoda333 (author)  GinaT8 months ago
Please do, and if you do don't skip the "More Fun Before Cleaning Up." When I did it I showed it to my 8 year old brother and he got a real kick out of it!
nightmare_man8 months ago
You don't need to go through such hassle to create red cabbage ph indicator. No need to boil the water, just put your cabbage and water in a blender, liquify then strain and collect your indicator juice. The active ingredient (flavin an anthocyanin) is water soluble.
yoda333 (author)  nightmare_man8 months ago
I didn't try blending the cabbage but it really doesn't take long too boil. I will try blending next time I do this. Thanks!
GinaT yoda3338 months ago
our 8 yr old and i will boil our cabbage... and then eat it:)
yoda333 (author) 8 months ago
I must say. If you do this experiment, you have to do the last part. It looks really cool!!!
Kiteman8 months ago
Nice job!
yoda333 (author)  Kiteman8 months ago
Thank you Kiteman.
pmn93938 months ago

So, you have urine or saliva in your tapwater. Might wanna get a purification filter for that.

yoda333 (author)  pmn93938 months ago
Are you sure this means I have urine or saliva in my tap water? Shadowjfaith seems to have a more pleasant explanation. How would they get in my tap water anyways?
carlos66ba8 months ago

The fact that red cabbage is a pH indicator is well known, but in any case I like your instructable: you set-up a clear experiment and proceed to conclusions.

yoda333 (author)  carlos66ba8 months ago
Thanks you.