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Red Cabbage Indicator: Check Notes & Experiments

Red Cabbage Indicator Notes: Chemical substances called indicators can be added to an acidic, basic, or neutral solution. A purple-coloured solution called  the red cabbage indicator  determines if a product is acidic or basic. Red cabbage, commonly found in homes, can make a pH indicator solution. The pigment molecule flavin or anthocyanin found in cabbage changes colour based on the solution’s acidity. When the purple solution reacts with something acidic, it turns red, and when it reacts with something basic, it turns green. If a substance does not change its colour, it is neutral. Let’s try a red cabbage indication experiment to see what happens.

In this article, we have provided detailed notes on the red cabbage indicator. Students can read the notes and learn all important topics included in the red cabbage indicator. Continue reading this article to learn about red cabbage indicators, olfactory indicators examples etc.

Red Cabbage Indicator Notes: Indicators

An indicator is a ‘dye’ that changes colour when put into an acid or a base. An indicator gives different colours in acid and base. Thus, an indicator tells us whether the substance we are testing is an acid or a base by its colour change.

There are three types of indicators:

• i. Natural indicators
• ii. Synthetic indicators
• iii. Olfactory indicators

CLEAR YOUR CONCEPTUAL DOUBTS ON RED CABBAGE INDICATOR

Natural Indicators

Natural indicators are indicators derived from natural sources such as vegetables and fruits. Litmus, turmeric, red cabbage, China rose, and other natural indicators are commonly used to determine whether a product is acidic or basic.

Learn Exam Concepts on Embibe

The hydrogen ions \(\left({{{\text{H}}^ + }} \right)\) and hydroxyl ions \(\left({{\text{O}}{{\text{H}}^ – }} \right)\) in a solution are detected using these natural indicators. Some changes in the natural indicator are given as below:

Study Acids and Bases Concepts

Synthetic Indicators

Synthetic indicators are those that have been created in a laboratory. Phenolphthalein, methyl orange, and other synthetic markers are synthetic indicators. Another example of a synthetic indicator is litmus paper.

Methyl orange shows red colour in acidic solution and yellow colour in basic solution. Phenolphthalein turns colourless in acidic solution and pink in the basic solution.

Olfactory Indicators

Olfactory indicators help identify whether the given solution is acidic or basic by changing its smell instead of colour.

Onion, vanilla and cloves are examples of olfactory indicators.

Importance of Indicators

The nature of a material is important in Biology, Chemistry, Engineering, Water Purification, Agriculture, Forestry, Food Industry, Environment, Water Treatment, Medicine, Nutrition, and other fields.

Practice Exam Questions

Red Cabbage Indicator

The natural pH indicator in red cabbage juice changes colour based on the solution’s acidity. Flavin is the pigment in red cabbage that produces the red colour shift (an anthocyanin). Apple skins, plums, and grapes contain flavin, a water-soluble pigment. The indicator turns red when exposed to very acidic solutions, purple when exposed to neutral solutions, and greenish-yellow when exposed to basic solutions.

Red Cabbage Experiment

Let’s perform the Red Cabbage experiment now

Materials Required for Red Cabbage Experiment

• i. A red cabbage
• ii. A sharp knife
• iii. A pot of boiling water
• iv. Household liquids to test (vinegar, baking soda, juices, soaps, bleach, ammonia)
• v. Glass bowl 
• vi. Something to stir

The aim is to create a natural indicator using red cabbage.

Red Cabbage Experiment Procedure

• 1. Cut around \(2 – 3\) cups of red cabbage.
• 2. Boil the red cabbage pieces in a kettle of water for a few minutes. Turn off the heat and let it sit for \(10\) minutes after it has boiled.
• 3. Strain the water and set it aside to cool in a glass bowl.
• 4. Pour some into transparent cups or glasses once it has cooled and experimented with different liquids.
• 5. Gently stir or swirl the solution to see how it changes.
• 6. It will be noticed that the colour of the substance will change depending on whether it is acidic or basic.

Observation

Acidic chemicals turn the solution purple to red or pink in appearance. The purple solution becomes blue when neutral chemicals are added. The purple solution turns green or yellow when basic chemicals are added.

Hence, red cabbage is a natural indicator.

Making \({\text{pH}}\) paper

Red cabbage can also be used to make \({\text{pH}}\) paper strips in addition to the solution. We can use a filter paper (or a coffee filter) dipped in the concentrated red cabbage solution.

Soak it for a while, then remove the paper and dry it. After it has dried, cut the paper into little strips, which can then be used to test the \({\text{pH}}\) of various liquids; see what colour you get by putting a drop of liquid on the test strip. Depending on whether the strip is acidic or basic, it turns red or green.

Red Cabbage \({\text{pH}}\) Indicator Colour Chart

Below given is the table which indicates the colour according to the \({\text{pH}}\) of the liquids:

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Disadvantages of Using Red Cabbage Juice as an Indicator

• i. Slower than litmus paper.
• ii.It contaminates the solution.
• iii.It does not tell acid strength.
• iv. It requires more solutions than litmus paper.
• v. If the solution is dark, the colour change is not visible.

This article studied how indicators change their colour or characteristic smell to detect that the given substance is acidic or basic. We also studied that the red cabbage indicator is a natural indicator and changes to red in acidic solutions, purple in neutral solutions and greenish-yellow in basic solution. We now know how to execute an experiment to make red cabbage a natural indication.

PRACTICE QUESTIONS RELATED TO RED CABBAGE INDICATOR

FAQs on Red Cabbage Indicator

Q.1: How does the red cabbage indicator work? Ans: When red cabbage is treated with an acid or a base, it produces anthocyanin, a water-soluble pigment that changes colour. In acidic situations with a \({\text{pH}}\) less than \(7,\) the pigment turns red, and in alkaline (basic) environments with a \({\text{pH}}\) of more than \(7,\) the pigment turns bluish-green.

Q.2: Is red cabbage a good indicator? Ans: Red cabbage is a good indicator, but it has its disadvantages which are as follows: It is slower than litmus paper, it contaminates the solution, it does not tell about the acidic or basic strength, it requires more solutions than litmus paper, and if the solution is dark, the colour change is not visible.

Q.3: How long does the red cabbage indicator last? Ans: Over time, the red cabbage indicator solution will acquire an odour and mould. Red cabbage indicator solution that has not been used can be kept refrigerated for up to one week in a stoppered flask.

Q.4: Why is the red cabbage indicator called an acid-base indicator? Ans: The red cabbage indicator is called an acid-base indicator because in acidic situations with a \({\text{pH}}\) less than \(7,\) the pigment turns red, and in alkaline (basic) environments with a \({\text{pH}}\) of more than \(7,\) the pigment turns bluish-green.

Q.5: How to make the red cabbage a \({\text{PH}}\) indicator? Ans: The red cabbage can be made a \({\text{pH}}\) indicator by following these steps: i. Take a red cabbage and cut off about \(2 – 3\) cups. ii. Boil the pieces of red cabbage in a pot of water for a couple of minutes. After it is boiled, turn the heat off and let it sit for ten minutes. iii. Strain the water in a glass bowl and let it cool. iv. Once it is cooled, pour some into clear cups or glasses and experiment with different liquids. v. Stir or swirl the solution gently and observe the changes. It will be observed that the colour of the substance will change according to its acidic or basic characteristics.

We hope this detailed article about the red cabbage indicator will be helpful to you. If you have any queries related to the article, or in general, about the red cabbage indicator, please ping us through the comments section, and we will get back to you at the earliest.

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Red Cabbage Science Experiment

I’m not a big fan of cabbage except for when it’s used for science! Food science is super cool and is awesome for kids. This isn’t the sweetest-smelling science experiment we have done, but once you get past the smell this cabbage science experiment is fascinating chemistry . Find out how to test pH with red cabbage!

HOW TO MAKE RED CABBAGE INDICATOR

RED CABBAGE PH INDICATOR

There are tons of fun pH science experiments for kids, but one of the most thrilling and satisfying is the cabbage pH indicator science experiment.

In this experiment, kids learn how cabbage can be used to test liquids of varying acid levels. Depending on the pH of the liquid, the cabbage turns shades of pink, purple, or green! It’s incredibly cool to watch, and the kids love it!

Read more about the pH Scale here and look for a free printable!

This makes a great middle school and elementary age science activity (and up!), but adult supervision and assistance are still required!

WATCH THE RED CABBAGE EXPERIMENT VIDEO:

WHAT IS AN INDICATOR IN CHEMISTRY?

pH stands for power of hydrogen . The pH scale is a way to measure the strength of an acid or base solution, and is numbered from 0 to 14.

Distilled water has a pH of 7, and is considered a neutral solution. Acids have a pH lower than 7 and bases have a higher pH higher than 7.

If you ask the kids about what types of things around the house are acidic, they might say vinegar or lemons. An acid is usually recognized as something with a sour or sharp taste.  Baking soda is an example of a base.

An indicator is one way to work out the pH of a solution. Good indicators give a visible sign, usually a color change, when they come into contact with acids or bases. Like our red cabbage indicator below.

Why can red cabbage be used as an indicator to test pH?

Red cabbage contains  anthocyanin, which is a water-soluble pigment. This pigment changes color when mixed with an acid or a base. Redder when mixed with an acid and greener when mixed with a base.

TIP: Here’s a simple pH scale for kids with a little extra information. Plus it gives you a few more items to test once you have made your red cabbage pH indicator!

Click here to get your printable science experiment worksheets!

RED CABBAGE EXPERIMENT

Let’s make an indicator and test it out on common household solutions!

Grab a head or two of red cabbage and let’s get started! Even if your kids swear they hate cabbage, they will be loving it (at least for science sake) after this awesome cabbage chemistry experiment.

• Red cabbage
• Several jars or small containers
• Lemons (grab a few for a couple of extra science activities you will find below)
• Baking soda
• Other acids and bases to test (see more items to test below)
• pH test strips (optional but older kids will enjoy the added activity)

STEP 1. S tart by cutting the red cabbage roughly into small pieces.

The cabbage indicator can be prepped ahead of time but I love when you can involve kids in the whole process!

STEP 3. Place your cut up cabbage in a medium saucepan and boil for 5 minutes.

STEP 3. After the 5 minutes, cover and let it rest for 30 minutes.

STEP 4. Go ahead and carefully pour the liquid into the jars. This is your acid-base indicator! ( You can dilute the cabbage juice and it will still work )

USING RED CABBAGE PH INDICATOR

Now it’s time to test the pH of different items. We have a few common acids and bases for you to start with. This experiment is set up so that you add some of the acid or base to the jar of red cabbage juice, and observe the color change.

Please take care when mixing different items into your cabbage pH indicator. Adult supervision is recommended at all times. This NOT an edible science experiment!

You can find even more solutions to test out! Depending on your kid’s interest levels and needs, you could turn this into a huge science experiment. This red cabbage experiment also makes a terrific science fair project !

Before your kids start testing each one, have them make predictions about what color change they will see. Remember, red color is acidic and green color is basic.

Here are a few acids and bases to test…

1. LEMON JUICE

Squeeze lemon juice into one of the jars. What color did it change to?

What else can you do with lemons? We have a couple of fun ideas for exploring fun chemistry with this fruit!

• Erupting Lemon Volcano
• Make Fizzing Lemonade

2. BAKING SODA

Put a teaspoon of baking soda into a cabbage juice jar. Notice what happens! What color did the indicator change to?

If you have ever experimented with baking soda and vinegar, your kids may already know that baking soda is a base and vinegar is an acid. Vinegar is also a great liquid to use to test with your red cabbage indicator!

EXPERIMENT WITH: Baking Soda and Vinegar Science

4. BLACK COFFEE

Coffee is a common drink for many people. But is it an acid or a base?

EXTEND THE ACTIVITY

Test other liquids to compare whether they are acids or bases. To extend the activity, use pH test strips to determine the exact pH of each liquid. If you dissolve them in water or the indicator, you can also test the pH of solids, like sugar or salt .

DIY: Make your own pH strips by soaking coffee filters in the cabbage juice and hang to dry, cut in strips!

Kids will have a blast testing a variety of kitchen pantry ingredients with their cabbage juice pH indicator science project! You may even need to buy more red cabbage the next time you go to the store. Simple chemistry is cool! Check out 65 chemistry experiments for kids for more ideas!

USE THE SCIENTIFIC METHOD

This cabbage PH science experiment is a fantastic opportunity to use the scientific method and start a journal using the free mini pack above. You can read about incorporating the scientific method here , including more information on the independent and dependent variables .

The first step in the scientific method is asking a question and developing a hypothesis. What do you think will happen if_______________? I think the_________ will___________if___________. This is the first step to diving deeper into science with kiddos and making connections!

SCIENCE FAIR PROJECTS

You can also easily turn your cabbage science experiment into a fantastic presentation along with your hypothesis. Check out the resources below to get started.

• Easy Science Fair Projects
• Science Project Tips From A Teacher
• Science Fair Board Ideas

More Fun With Acids and Bases

Printable Science Projects For Kids

If you’re looking to grab all of our printable science projects in one convenient place plus exclusive worksheets and bonuses like a STEAM Project pack, our Science Project Pack is what you need! Over 300+ Pages!

• 90+ classic science activities  with journal pages, supply lists, set up and process, and science information.  NEW! Activity-specific observation pages!
• Best science practices posters  and our original science method process folders for extra alternatives!
• Be a Collector activities pack  introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
• Know the Words Science vocabulary pack  includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
• My science journal writing prompts  explore what it means to be a scientist!!
• Bonus STEAM Project Pack:  Art meets science with doable projects!
• Bonus Quick Grab Packs for Biology, Earth Science, Chemistry, and Physics

This is an awesome experiment to do, even for older kids! It shows them that chemistry is very much a part of our lives and are closer to us than we think! I’m sure kids would love it 🙂

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• Acids, Bases and Salts
• Red Cabbage Indicator

Red cabbage Indicator

Red cabbage indicator is a purple-coloured solution that is used to test whether substances are acid or base . Red cabbage that is often found in homes can be used to prepare a solution that acts as a pH indicator. The cabbage basically contains a pigment molecule called flavin or anthocyanin that changes colour depending on the acidity of the solution.

Normally, the purple solution turns red in colour when it combines with something acidic and it turns bluishg-green in colour when it combines with a base. If the substance does not cause the colour to change then it is mostly neutral.

Red Cabbage Indicator pH Colours

Below are the different pH levels and the colours that are obtained during the red cabbage indicator test.

Let us conduct an experiment and observe the results.

To determine which chemicals are bases and which are acids.

Apparatus Required

• Red cabbage leaves
• Lemon juice
• Soda(baking soda)
• Glass jars of a similar size
• Cut the cabbage leaves into small pieces.
• Boil separate cups of water as they will be required to submerge your pieces later on.
• Place the cabbage pieces into a bowl and pour the water in the bowl. Keep it for several minutes so that the cabbage pieces get soaked. You can also use a mixer to grind the leaves and obtain a solution.
• If you are not using the mixture then separate the juice from the leaves.
• Take glass jars and place them about two inches apart. Pour every chemical (lemon juice, vinegar, detergent and soda) into each jar.
• Now to determine whether the substance is a base or an acid pour the cabbage juice into each jar. Here, if the mixture turns pink or red the chemical is an acid and if it turns bluish-green the chemical is usually a base.

This experiment can easily be conducted even in the house and can be used to test different substances which are easily available.

Safety Tips

•  Since the chemical indicator is used to test acids and bases it is always advised to use safety goggles and gloves especially while dealing with strong or concentrated chemicals.
• Chemicals can be washed down the drain safely with water.
• A neutralisation experiment can also be done along with the test.

Making pH Paper

In addition to the solution, pH paper strips can also be created using red cabbage using the steps given below: 1. Firstly, use a filter paper (or coffee filter) and dip it in the concentrated solution obtained from red cabbage.

2. Soak it for some time and later take the paper and dry it.

3. Once it is dried, cut the paper into small strips and they are ready to be used for testing the pH of different solutions.

4. Pour a drop of liquid on the test strip and see what colour is obtained. The strip also turns either red or green depending on whether it is acidic or basic.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

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January 26, 2012

Cabbage Chemistry--Finding Acids and Bases

A colorful chemistry challenge from Science Buddies

By Science Buddies

Key concepts Chemistry Acids Bases Light

Introduction You might have done experiments with well-labeled acids and bases in school, but have you ever wondered whether a certain food or chemical around the house is an acid or a base? You can find out using a red cabbage to make an indicator solution.

When two or more ingredients are entirely dissolved in one another, you have a solution. For example, mixing salt with water creates a clear solution, even though the salt is there and the solution tastes salty. When mixed with water, whether a chemical "donates" a charged particle (called an ion) to the solution—in this case, a hydrogen ion—or "accepts" one from it determines whether it's an acidic or basic solution. An indicator changes color when exposed to such a mixture, depending on whether the solution is acidic or basic.

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Background Acids are solutions that lose hydrogen ions and usually taste sour. Some very common household solutions are acids, such as citrus fruit juices and household vinegar. Bases are solutions that pull hydrogen ions out of solution and onto themselves, "accepting" them, and usually feel slippery. Bases have many practical uses. For example, "antacids" like TUMS are used to reduce the acidity in your stomach. Other bases make useful household cleaning products.

To tell if something is an acid or a base, you can use a chemical called an indicator. An indicator changes color when it encounters an acid or base. There are many different types of indicators, some that are liquids and others that are concentrated on little strips of "litmus" paper. Indicators can be extracted from many different sources, including the pigment of many plants. For example, red cabbages contain an indicator pigment molecule called flavin, which is a type of molecule called an anthocyanin. Very acidic solutions will turn an anthocyanin red whereas neutral solutions will make it purplish and basic solutions will turn it greenish-yellow. Consequently, the color an anthocyanin solution turns can be used to determine a solution's pH—a measure of how basic or acidic a solution is.

Materials •    A small red cabbage •    Pot of boiling water •    Strainer •    Two large bowls or pots •    Grater •    Tablespoon measurer •    Large spoon (optional) •    Three or more small, white paper cups (small, white paper drinking glasses or dishes will also work) •    Goggles or other protective eyewear •    Lemon or lime juice •    Vinegar •    Bleach-based cleaning product •    Other foods to test, such as clear soda pop, baking soda solution, egg whites, tomatoes, cottage cheese (optional) Preparation •    Grate a small red cabbage. If you do not want to grate the entire cabbage, grating half of a cabbage should be enough. Put the fine, pulpy grated cabbage into a large bowl or pot. •    Boil a pot of water. Use caution when handling the boiling water. Pour the boiling water into the bowl with the cabbage pulp until the water just covers the cabbage. •    Leave the cabbage mixture steeping, stirring occasionally, until the liquid is room temperature. This should take at least half an hour. The liquid will become red or purplish-red in color. •    Place a strainer over another large bowl or pot and pour the cabbage mixture through the strainer to remove the cabbage pulp. Press down on the pulp in the strainer, such as by using a large spoon, to squeeze more liquid out of the pulp. •    In the bowl, you should now have only liquid that will either be purple or blue in color. This will be your indicator solution, which you will use to test the pH of different liquids. •    Children should wear goggles or other protective eyewear and adults should supervise and use caution when handling bleach and vinegar, because they can irritate eyes and skin. Procedure •    Fill a small, white paper cup, drinking glass or white dish with one tablespoon of your cabbage-indicator solution. What is the color of your indicator solution? •    Add drops of lemon or lime juice to the indicator solution until you see the solution change in color. Gently swirl the solution and make sure the color stays the same. What color did the solution become? •    The color of the solution will change depending on its pH: Red color indicates the pH is 2; Purple indicates pH 4; Violet indicates pH 6; Blue indicates pH 8; Blue-green indicates pH 10; Greenish-yellow indicates pH 12. •     Based on its color, what is the pH of the lemon or lime juice solution? •    In another small, white paper cup, add one tablespoon of your original cabbage-indicator solution. Add drops of vinegar until you see the solution change color. What color did the vinegar solution become? What is the pH of the solution? •    In a third small, white paper cup, add one tablespoon of your original cabbage-indicator solution. Handling it with caution, add drops of the bleach cleaning product until you see the solution change color. What color did the bleach solution become, and what does this indicate about its pH? •    If you want to test the pH of other foods, again add one tablespoon of your original cabbage-indicator solution to a small, white paper cup and add drops of the food until you see the solution change color. If the food is not in liquid form, crush it or dissolve it in a small amount of water before adding it to the indicator solution. What color did the solution become, and what does this indicate about its pH? •     Extra: There are other vegetables and fruits that can be used to make pH indicators as well: red onion, apple skins, blueberries, grape skins and plums. Which different sources of pigment produce the best indicators? •     Extra: You can use an indicator solution to write secret messages. Just use full-strength lemon juice to write an invisible message on paper and let the message dry. To reveal the message, paint cabbage-indicator over the paper with a paintbrush. Observations and results Did the indicator solution change color when you added the lime or lemon juice, vinegar and bleach? Did the solution color indicate that the lime or lemon juice and vinegar were acidic (had a lower pH) and that the bleach was basic (with a higher pH)?

A solution with a pH between 5 and 7 is neutral, 8 or higher is a base, and 4 or lower is an acid. Lime juice, lemon juice and vinegar are acids, so they should have turned the indicator solution red or purple color. Bleach is a strong base, therefore it should have turned the indicator solution a greenish-yellow color.

How basic or acidic a solution is depends on the amount of hydrogen ions in it. A basic solution accepts hydrogen ions (or donates electron pairs as hydroxide ions) whereas an acidic solution donates hydrogen ions (or accepts electron pairs). An indicator, like anthocyanin, responds to the levels of hydrogen ions in the solution. Anthocyanin and other biological pigments absorb certain wavelengths of light and reflect others, and it is the reflected light we see that makes them appear a certain color. Depending on the levels of hydrogen ions in the solution, the indicator pigment undergoes a chemical reaction that changes its chemical structure, making it reflect a different wavelength of light and thereby change color.

Cleanup Dilute the bleach solution with water before pouring it down a drain. (Remember to keep your goggles on when you do this.)

More to explore "Experiments with Acids and Bases" from Fun Science Gallery "Acids and Bases Are Everywhere" from Rader's Chem4Kids.com "Acids, Bases, and the pH Scale" from Science Buddies "Cabbage Chemistry" from Science Buddies This activity brought to you in partnership with Science Buddies

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How to make a red cabbage pH indicator

September 24, 2021 By Emma Vanstone Leave a Comment

Red cabbage indicator is a simple way to tell whether a substance is an acid or alkali .

Acids can be found in the food we eat, in our bodies and around the home. Some acids, especially those found in cleaning products, can be very harmful, so take care when using them and always read their hazard labels.

Alkalis are a group of chemicals that react with acids. Substances such as soap are alkalis and bicarbonate of soda, which we use in baking, and also harmful things like bleach are alkalis.

You can make a straightforward red cabbage pH indicator to determine whether a substance is an acid or alkali. This activity is a great way to introduce the pH scale to kids !

What is a pH indicator?

We use a substance called an indicator to test the pH of something. An indicator will change colour in the presence of an acid or alkali. The pH scale goes from 0 to 14. A substance with a pH of 0 is a strong acid, pH 14 is a strong alkali, and pH 7 is neutral.

You can make an indicator using red cabbage.

What you need to make a red cabbage indicator

• Red cabbage – chopped
• Cups or small containers
• Different substances to test – baking soda, vinegar, lemon juice and lime juice all work well.

Place the chopped cabbage into the pan and cover it with water.

Simmer for 10 minutes.

Sieve the water and cabbage into a jug – you will notice that the cabbage liquid is very purple.

Leave to cool for about 30 minutes.

Add a small amount of each test substance to a separate cup or container, and try to keep the amount of test substance the same.

Use a pipette to drop about 20ml of red cabbage indicator into each cup and record the colour the indicator changes to.

Safety note

Wear safety goggles if using strong acids/bases.

An adult should help with the chopping and heating of the cabbage.

Red Cabbage Indicator pH Colours

Universal Indicator pH colours

Notice that the colours for acids and alkalis are different when using a universal indicator.

When using the red cabbage indicator, the colour of the liquid will change from purple to red if it is an acid and from purple to green if it is an alkali. The different shades of colour will depend on the strength of the acid or alkali. The substance is said to be neutral if there is no colour change.

How does the pH indicator work?

Acids and bases are opposites; acids have a low pH, and bases have a high pH.

Red cabbage contains a pigment called anthocyanin, which is what changes colour.

More Red Cabbage Indicator Experiments

Make colour changing fizzy potions !

Make your pH test strips by soaking filter paper in red cabbage indicator and leaving it to dry. Once dry, cut the filter paper into strips and dip it into test substances. Try testing milk, fizzy drinks or soap. Can you predict their pH before testing?

Try using beetroot juice instead of red cabbage; which works best?

You could also try blowing into the indicator. What happens?

A pH indicator can also be made from red poinsettia leaves !

What happens when you blow into the red cabbage indicator?

The indicator should turn red as the carbon dioxide you breathe out reacts with the water to form carbonic acid.

Last Updated on October 16, 2023 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

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Chem lab 2 - LAB REPORT

Organic chemistry i (chem 3323), texas a&m university-kingsville.

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Red cabbage ph indicator, october, 2019, peter isibor k, in this experiment a ph indicator using the anthocyanidin compounds in red cabbage will be, made. a colorimetric ph indicator is a chemical compound added in small amounts to a, solution, so the ph of the solution can be determined visually. these indicators are frequently, employed in titrations in analytical chemistry and biology. anthocyanins can be employed as, colorimetric compounds because they change color at different ph values. the anthocyanidin, motif exhibits subtle structural changes dependent on fluctuation in ph. in an acidic, environment with a ph less than 7 the compound takes on the form. while in a neutral, environment with a ph equal to 7 it is purple. because of these color changes at different ph, values, it is possible to determine the ph of a solution based on the color that this indicator, turns. ph indicators such as anthocyanidin are added to solutions in minute quantities because, it exhibits strong chromophores to begin with. this quality along with the ability to achieve, structural change at different ph values establishes them as superior colorimetric ph indicators., in plants, anthocyanins are found in many flowers and fruits of plants and may serve a, protective role against extreme temperatures. the absorbance pattern responsible for the red, color of anthocyanins may be complementary to that of green chlorophyll in, photosynthetically-active plant tissues..

deionized water wasn’t used. In this case, attempt the procedure again more diligently. After extracting the anthocyanidins into the water, remove the solid cabbage pieces via vacuum filtration using either a Buchner or Fritted Funnel vacuum filtration. Make sure to use a course frit for the fritted funnel if employing this method of filtration. For this experiment we are interested in keeping the liquid and discarding the solid remains into the trash. Label seven test tubes with the following information and place them in a test tube rack. Be sure to add the specific amount described to each test tube and place them in a test tube rack, using a 10 ml graduated cylinder for precision being sure to read to the bottom of the meniscus. Employ an analytical balance for weighing the solids. To each test tube ad 3 ml of the red cabbage extract. Make sure to stir each solution with a glass rod to ensure complete dissolution and consistency with color throughout the test tube. The acid-base reaction between the chemical compounds and the anthocyanidins in the cabbage juice occurs very rapidly. Describe detailed observations of color changes in the lab notebook. Using rubber stoppers, thoroughly mix the 5 ml of 1. M acetic acid with the 0 grams of sodium acetate. Add 3 ml of the red cabbage extract to test tubes 8 and 9. Be sure to swirl the test tubes to mix thoroughly and record the observations. Next add 3 drops of 12 M Hydrochloric acid to both test tubes. Test tube 8 should have changed color within the addition of a few drops of the HCl. Test tube 9 should require more HCl before a color change is noted. Continue to add the 12 M hydrochloric acid 3 drops at a time to test tube 9 until a distinct color change is seen. Record observations. Do not add more than 30 drops

Test Tube No. and Substance Amount Color 1 M Hydrochloric acid 1 ml Pinkish red 1 M Acetic Acid 1 ml Pink Ascorbic acid (Vitamin C) .111 g Hot Pink Nothing (non buffer) N/A Purple Sodium Bicarbonate ( Anhydrate, Carbonate)

.108 g Olive Green

1 M Ammonia 1 ml Green Control # 4 + Di H2O 5 ml Lavender 1 M Acetic Acid + Sodium Acetate

5 ml + 0 g Light Pink; 8 drops

Calculations

None for this lab

Once 10-15 grams of red cabbage was obtained and washed, the red cabbage was torn into small pieces and placed into a large beaker with 150 ml of deionized water. The large beaker is then put onto a hot plate and the solution is then brought to a boil. The solution is boiling until the water is a dark purple color. Once the dark purple color is reached the beaker is carefully removed from the hot plate and allowed to cool. Then 8 test tubes are labeled, and the specific amount of each compound/chemical is put into its designated test tube. In test tube one, 1 ml of 1 M Hydrochloric acid mixed with the red

cabbage juice turned a pinkish red. In test tube two, 1 ml of 1 M Acetic Acid mixed with the red cabbage juice turned Pink. In test tube three, 0 g of Ascorbic acid mixed with the red cabbage juice turned Hot Pink. In test tube four, the red cabbage juice was put in the test tube because it was the non- buffer and since it was only the red cabbage juice in the test tube it was Purple. In test tube five, 0 g of Sodium Bicarbonate (Anhydrate) mixed with red cabbage juice turned an olive-green color. In test tube six, 1 ml of 1 M Ammonia plus the red cabbage juice turned green. In test tube seven, the control (test tube 4) plus 5 ml of distilled water turned lavender. In test eight, 5 ml of 1 M Acetic Acid and 0. g of sodium Acetate was mixed with 3 ml of the red cabbage extract it turned a light pink with 8 drops of HCl. Observations were recorded.

Organic Chemistry I Chem 3123 laboratory Manual Jason Abrams

Pre-Lab Questions

• Coumarin Isocoumarin Chromone
• The components in the solution
• Phenol Red, Cresol Red, m-Nitropheno, Thymol blue

by Unknown Author is licensed under

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Course : Organic Chemistry I (CHEM 3323)

University : texas a&m university-kingsville.

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From kitchen to classroom

• 1 Introduction
• 2 Separation techniques
• 3 Red cabbage rainbows
• 4 Making bath bombs
• 5 How to make butter
• 6 Tricking taste buds with toothpaste
• 7 Kitchen roll chromatography
• 8 Investigating surface tension with milk
• 9 Chalky spinach
• 10 How to purify water

Red cabbage rainbows

Five out of five

In this activity, learners create rainbows using drops of red cabbage indicator homemade indicator paper using items you can find in the kitchen cupboard 

In this video,  education coordinator  Rosie demonstrates how you can make red cabbage indicator, a dark purple liquid which changes colour when it comes into contact with an acid or an alkali, and use it to create rainbows. This simple activity can be set for learners to try at home with a responsible adult or used as a classroom experiment.

Equipment list

• Red cabbage
• Paper and plastic wallet
• Kitchen roll
• Lemon juice (acid)
• Soda bicarbonate (alkali)
• Washing powder (alkali)
• Pots and pans
• Paint brush

Health and safety

• If this activity is set for the students to try at home it is important that a responsible adult is present at all times.
• Take care when using knives and boiling water.
• Do not drink the red cabbage indicator.
• Remember that some household substances can be harmful – make sure you read any warnings on the bottle or packet before you decide whether or not to use it.

Activity instructions

Preparing the red cabbage indicator and the homemade indicator paper.

• Take three leaves of the red cabbage and chop them into small pieces.
• Put the chopped up red cabbage into a pan, add enough water so the cabbage is just covered. Boil the cabbage for about ten minutes. Another way to make the indicator is by blending the leaves or leaving them to soak overnight. But if you boil the cabbage, then you can make indicator and have cabbage for your tea!
• Once the red cabbage and the water is cool, put a couple of pieces of kitchen roll in a sieve and drain the red cabbage through it, collecting the water in a bowl underneath. The red cabbage will have dyed the water purple creating indicator, and will also stain the kitchen roll to make the indicator paper.
• Leave the dyed kitchen roll to dry.

Preparing the acids and alkalis you find in the kitchen

• When using liquids, such as lemon juice, pour a small amount into a container.
• When using powders such as washing powder or bicarbonate of soda, mix a small amount with some water in a container.

Creating rainbows using drops

• Draw a rainbow onto a piece of paper and put it inside a poly pocket.
• Use a paintbrush to drop the red cabbage indicator onto the rainbow.
• Use a separate paintbrush to add some acids and alkalis that you can find in your kitchen to the drops of red cabbage indicator. Watch as some of the colours of the rainbow appear. 

Creating rainbows using homemade indicator paper

• Once your homemade indicator paper is dry you can paint a rainbow onto the paper using the acids and alkalis that I’ve found in the kitchen.
• Add an acid or an alkaline onto your paintbrush and then paint it directly on the indicator paper. You should see that the paper instantly changes from purple to a colour – the colour will depend on which acid or alkali is used.

Explanation

Red cabbages contain anthocyanins, these change colour when they come into contact with an acid or an alkali. For example, acidic lemon juice turn the red cabbage indicator line, alkaline washing powder turns it green and alkaline bicarbonate of soda turns it blue. Have a go with your learners and discover what other acids and alkalis you can find in the kitchen cupboard. 

Additional activities and lesson notes

Try making a pH ‘rainbow wand’ and find context and guidance for using these experiments in the classroom, during open days and for public events. Explore the additional resources at the bottom of this page and check out the lesson notes below for more information.

Skills development

Children will develop their working scientifically skills by:

• Drawing conclusions and raising further questions to be investigated, based on their data and observations
• Asking their own questions about scientific phenomena
• Grouping and classifying things

Learning outcomes

Children will:

• Group substances according to whether they are acidic, neutral or alkaline
• Compare and group together everyday materials on the basis of their properties

Concepts supported

Children will learn:

• That substances can be acidic, neutral or alkaline, and that tests can be performed to determine which of the three a substance is

Suggested activity use

You can use the activities described in the ‘Rainbow cabbage’ and ‘Red cabbage indicator experiments’ handouts for a whole-class investigation, allowing children to group substances into acids and alkalis. They will provide opportunity for discussion and questioning.

Alternatively, you could use this resource as part of a science week or at a science club.

Practical considerations

The red cabbage juice indicator can be prepared the prior to any lesson, which will save time.

A range of different substances to test will be required.

Also check out

• Download the Rainbow cabbage handout , originally designed to be shared with children and their parents or guardians during the Cambridge Science Festival 2013. It provides simple instructions for making and testing red cabbage indicator paper, and includes a colour comparison chart.
• Download the ‘Red cabbage indicator experiments’ handout as a PDF or editable Word document for guidance on how to do the ‘rainbow wand’ experiment using red cabbage juice, plus further background information about pH, acids and alkalis.
• More simple experiments using everyday equipment which your learners can try at home or you can bring to the classroom on our  YouTube playlist .
• Read the CLEAPSS guidance on practical activities for pupils at home during extended periods of school closure,  GL339 .
• Read the SSERC guidance for  primary home learning . 

Red cabbage rainbows - teacher notes

Rainbow cabbage handout, red cabbage indicator experiments.

Introduction

Separation techniques

Making bath bombs

How to make butter

Tricking taste buds with toothpaste

Kitchen roll chromatography

Investigating surface tension with milk

Chalky spinach

How to purify water

• Practical experiments
• Practical skills and safety
• Acids and bases
• Applications of chemistry
• Making predictions
• Observing and measuring

Specification

• C6.1.4 recall that relative acidity and alkalinity are measured by pH including the use of universal indicator and pH meters
• C3.3k describe techniques and apparatus used to measure pH
• Titration is used to determine, accurately, the volumes of solution required to reach the end-point of a chemical reaction. An indicator is normally used to show when the end-point is reached. Titre volumes within 0.2 cm³ are considered concordant.
• Indicators are weak acids for which the dissociation can be represented as: HIn(aq) + H₂O(l) ⇌ H₃O⁺(aq) + In⁻(aq)
• An indicator is normally used to show when the end-point is reached.
• The pH scale is an indication of the hydrogen ion concentration and runs from below 0 to above 14.
• Acidic solutions have a higher concentration of H⁺(aq) ions than OH⁻(aq) and have a pH below 7.
• Alkaline solutions have a higher concentration of OH⁻(aq) ions than H⁺(aq) ions and have a pH above 7.
• 8. Investigate reactions between acids and bases; use indicators and the pH scale

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8: Acid, Bases and pH (Experiment)

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• Page ID 95543

• Santa Monica College

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• To set up and show how to use a pH indicator
• To determine the pH of common solutions
• To understand pH differences of acids and bases
• To learn to use a laboratory pH meter
• To understand relationship between pH and H+ ion concentration

A pH value is a number, usually between 0 and 14, that represents the acidity or basicity of a solution. The “pH” is always written with a lowercase “p” and an uppercase “H”, which stands for “power of hydrogen.” pH values are related to hydrogen ion (\(\ce{H^+}\)) concentrations.

The mathematical relationship between pH and \(\ce{H^+}\) is described by the equation

\[pH = - \log(\ce{H^+})\]

There is an inverse relationship between pH and \(\ce{H^+}\) ion concentration (in brackets, expressed in units of molarity , M). As the \(\ce{H^+}\) concentration decreases, the pH value increases, and vice versa. When the pH value is a whole number (e.g. pH 7), the number is equal to the negative exponent of the \(\ce{H^+}\) ion concentration.

\[\text{pH value} = X \ce{->} [\ce{H^+}] = 10^{-X} M\]

So for pH 7, the \(\ce{H^+}\) ion concentration is 10 -7 M.

The pH values of everyday chemicals typically range from pH 0 to pH 14. Values between 0 and 7 indicate an acidic solution. Values between 7 and 14 indicate a basic solution. A pH of exactly 7 indicates that a solution is neutral, neither acidic or basic. Pure water is usually pH 7.

The pH scale is shown below.

The lower the pH value, the more acidic the solution; the higher the pH value, the more basic the solution. Basic solutions are also called alkaline solutions. It should be noted that the pH scale does extend beyond 0 and 14. Strong laboratory acids typically have pH values less than 0 (negative pH values) and strong laboratory bases typically have pH values greater than 14. Thus, they are considerably more dangerous.

The concept of pH is widely used in all areas of science including agriculture, biology, engineering and medicine. Many commercial products use pH as an advertisement tool, such as shampoo and water; more recently, food and drink of certain pH has been touted as more healthful.

A pH indicator is a substance that, when a small amount of it is added to a solution of unknown pH, will change its color. This is a way to determine pH of a solution visually. The indicator used in this lab will be obtained from a natural source, red cabbage. Cabbage indicator yields a particular color depending on the pH of the solution. pH indicators are a good way to easily and quickly show the approximate pH by color when compared to a standard. An everyday example where a pH indicator is used is for testing a water sample from a swimming pool.

While pH indicators are useful for qualitative purposes, when an exact quantitative value is needed, a pH meter is used. A laboratory pH meter typically has a special probe capped with a membrane that is sensitive to \(\ce{H^+}\) ion concentrations. The meter reading shows an exact pH value of the solution probed.

pH meters are used to measure pH values of water samples, such as determining acidity of rainwater samples. Rain water is contains dissolved carbon dioxide that produces a weakly acidic solution. Rain naturally has a pH between 5 and 6. The pH of rain in parts of the U.S. is less than pH 5, which is harmful to aquatic life and human health. This is acid rain.

Living organisms are very sensitive to the effects of acids and bases in their environment. An excess of \(\ce{H^+}\) or \(\ce{OH^-}\) can interfere with the functioning of biological molecules, especially proteins. Thus, in order to maintain homeostasis and survive, organisms must maintain a stable internal pH.

A buffer is a solution whose pH resists change on addition of small amounts of either an acid or a base. To be a good buffer, a solution should have a component that acts as a base (takes \(\ce{H^+}\) out of solution) and a component that acts as an acid (puts more \(\ce{H^+}\) into solution when there is an excess of \(\ce{OH^-}\)).

The buffering capacity of a solution is tested by adding small amounts of acid (for example, \(\ce{HCl}\)) and base (for example, \(\ce{NaOH}\)) and checking the pH after each addition. If the pH changes only slightly, the solution is a good buffer. Eventually its buffering capacity will be exhausted, however, and the pH will change dramatically.

Materials and Equipment

400-mL beaker, ring stand, wire gauze, Bunsen burner, large test tubes, dropper pipet, stirring rod, wash bottle with distilled water, laboratory pH meter, 0.1 M acetic acid, 0.1 M \(\ce{NaC2H3O2}\), 0.1 M acetic acid (\(\ce{HC2H3O2}\)), 0.1 M hydrochloric acid (\(\ce{HCl}\)), 0.1 M sodium hydroxide (\(\ce{NaOH}\)), pH paper

Exercise appropriate caution when using the Bunsen burner .

Personal Protective Equipment (PPE) required: safety goggles, lab coat, closed-toe shoes Materials and Equipment

Experimental Procedure

Part a: preparing ph indicator and ph standards - instructor demo.

• Tear a few leaves of red cabbage into small pieces and place the leaves into a 500-mL beaker. Add about 500-mL of distilled water to this beaker. Make sure that all of the leaf pieces are completely submerged.
• Gently boil the mixture on heating plate until it appears dark purple in color (5-10 min). Turn off the heat and allow to cool (5 min).
• Add cabbage indicator solution to pH standard solutions, labeled 1-13. Students will record the colors of the pH standards.
• Each group will bring a small beaker to the front and take ~50 mL of the cabbage indicator back to their bench.

Part B: Qualitative Analysis for pH Values of Everyday Chemicals

• Obtain 10 large test tubes (clean, but may be wet). Label each test tube with the solutions to be tested.
• Pour about 3-mL of each solution into the appropriately labeled test tube.
• Using a dropper pipet, add an equal volume of cabbage indicator solution. If necessary, stir to mix with a clean stirring rod (rinse with distilled water between uses).
• Record the resulting color of the sample after mixed with the cabbage indicator. Compare this color with pH standards at the front of the laboratory to determine the pH of the sample. The color may be between the pH standard colors (e.g. green-blue instead of green or blue alone). For these, record the pH to 0.5 values (e.g. pH = 9.5 instead of 9 or 10).

Do not discard the contents in these test tubes as they will be used in the next section.

Part C: Quantitative Analysis for pH Values of Everyday Chemicals

• Plug the probe into one port on the side of the pH meter. Plug the AC adapter into the other side of the pH meter; plug the adapter into an electrical outlet. You should see a pH value reading.
• Prepare the probe to make pH measurements: remove from the storage bottle and thoroughly rinse the lower section of the probe with distilled water/wash bottle.

Note: Do not completely submerge the probe. The handle is not waterproof.

• Use the same ten test tubes containing samples from Part B. Or, complete steps 1 and 2 of Part B to obtain ten samples for analysis. Insert the pH probe directly into each test tube. SPECIAL CARE IS NEEDED WHEN INSERTING THE PROBES INTO THE TEST TUBES. The probes must NOT touch the glass rim of the test tubes or the pH blub can easily be broken and the probe destroyed.
• Record the pH value (to 0.01 pH) shown on the pH meter screen.
• After each pH measurement, the probe must be thoroughly rinsed with distilled water.
• When you are finished making measurements, rinse the probe with distilled water. Slide the cap onto the probe, and then screw the cap onto the storage bottle so the tip of the probe is immersed in the storage solution.

Part D: Effect of Buffers on pH

• Obtain 4 large test tubes. Label the test tubes A, B, C, and D.
• Add 10-mL of distilled water to tubes A and C.
• Add a 5-mL quantity of both 0.1 M H \(\ce{C2H3O2}\) (acetic acid) and 0.1 M \(\ce{NaC2H3O2}\) (sodium acetate) to tubes B and D. This mixture of acetic acid and sodium acetate is a buffer solution. Stir to mix completely.
• Using pH paper, determine the pH of the contents of each test tube (A-D). Use the stirring rod to dab a small drop of the solution to be tested onto a piece of pH paper. Then compare the color obtained to the pH scale on the instructor’s desk to determine the pH value. Record these pH values to 0.1
• Add 5 drops of 0.1 M (\ce{HCl}\) (hydrochloric acid) to test tubes A and B. Record the pH using pH paper.
• Add 5 drops of 0.1 M \(\ce{NaOH}\) (sodium hydroxide) to test tubes C and D. Record the pH using pH paper.

Lab Report: Acids, Bases and pH

Part a: color of red cabbage indicator with ph standards.

Parts B and C: pH of Everyday Chemicals

• What is an acidic solution? What is a basic solution?
• What is an alkaline solution?
• What is a pH indicator? What are common uses of pH indicators?
• Write the mathematical equation that relates pH value and \(\ce{H^+}\) ion concentration:
• Circle correct choice:

Acids have (high OR low) pH, and (high OR low) \(\ce{H^+}\) ion concentration.

Bases have (high OR low) pH, and (high OR low) \(\ce{H^+}\) ion concentration.

• When the \(\ce{H^+}\) ion concentration is expressed in brackets [\(\ce{H^+}\)], what are the units of the for \(\ce{H^+}\) ion concentration?
• Does a solution with pH 10 have equal, less or more \(\ce{H^+}\) ions than of a solution with a pH 6? Calculate the [\(\ce{H^+}\)] for both solutions, include units in your answer:
• For pH 10, [\(\ce{H^+}\)] = _________________
• For pH 6, [\(\ce{H^+}\)] = _________________
• The two methods of determining pH values (pH indicator versus pH meter) should show similar pH values for those solutions. What was different?
• Explain why rain is naturally acidic, but not all rain is classified as “acid rain.
• Here are examples of what an individual might do to reduce acid rain. For each, explain the connection to production of acid rain.
• avoid running a washing machine with a small load
• add additional insulation on a home hot water heater
• walking instead of driving to work

How to Make Red Cabbage pH Paper

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It's easy, safe, and fun to make your own pH paper test strips. This is a project that kids can do and that can be done from home, though calibrated test strips would work in a lab, too.

Key Takeaways: Red Cabbage pH Indicator

• The pigment that gives red or purple cabbage its deep color is a natural pH indicator.
• You can crush the cells of the cabbage to release the pigment and use it to make pH test strips. The test strips are made of coffee filters or paper towels.
• Cabbage juice changes to red in the presence of an acid (pH less than 7), is blue at neutral pH (pH around 7), and is purple in the presence of a base (pH greater than 7).

Difficulty: Easy

Time Required: 15 minutes plus drying time

What You Need

Basically, all you need is a red cabbage (or purple cabbage, if that's what they are called where you live), some form of porous paper, and a means of cutting and heating the vegetable.

• Red Cabbage
• Filter Paper or Coffee Filters
• Blender - optional
• Microwave - optional
• Dropper or Toothpicks - optional

The reason you want to cut up the cabbage (ideally blend it) is to break open the cells and release the anthocyanins that are the color-changing pigment molecules. Heat isn't strictly necessary, but it does make it easier to break up the cabbage. For the pH paper, the easiest porous paper to find is a paper coffee filter. If you have filter paper, you likely already have access to pH paper. However, filter paper has a smaller pore size than a coffee filter and is a superior choice. In a pinch, you can use a paper towel to make the pH paper.

Here's How

• Cut a red cabbage (or purple) into pieces such that it will fit into a blender. Chop the cabbage, adding the minimum amount of water needed to blend it (because you want the juice as concentrated as possible). If you don't have a blender, then use a vegetable grater or chop your cabbage using a knife.
• Microwave the cabbage until it's at the boiling point . You'll see the liquid boil or else steam rising from the cabbage. If you don't have a microwave, soak the cabbage in a small volume of boiling water or else heat the cabbage using another method.
• Allow the cabbage to cool (about 10 minutes).
• Filter the liquid from the cabbage through a filter paper or coffee filter. It should be deeply colored.
• Soak a filter paper or coffee filter in this liquid. Allow it to dry. Cut the dry colored paper into test strips.
• Use a dropper or toothpick to apply a little liquid to a test strip. The color range for acids and bases will depend on the particular plant. If you like, you can construct a chart of pH and colors using liquids with a known pH so that you can then test unknowns. Examples of acids include hydrochloric acid (HCl), vinegar, and lemon juice. Examples of bases include sodium or potassium hydroxide (NaOH or KOH) and baking soda solution. You can use cabbage pH paper to tell if something is an acid, a base, or neutral, but you can't get highly specific pH readings like you would using a pH meter. If the liquid you are testing is very deeply colored, you can dilute it with water without altering its pH value.
• Another way to use your pH paper is as a color-change paper. You can draw on pH paper using a toothpick or cotton swab that has been dipped in an acid or base.
• If you don't want colored fingers, soak only half of the filter paper with the cabbage juice, leaving the other side uncolored. You'll get less usable paper, but you will have a place to grab it.
• Many plants produce pigments that can be used as pH indicators . Try this project with some of the other common home and garden indicators . Most red or purple flowers and vegetables are pH indicators. Examples include beets, red roses, and purple pansies.
• If you spill the cabbage juice and stain a surface, you can get the stain out using ordinary household bleach.
• Howstuffworks. "Where does the color come from in purple cabbage?" science.howstuffworks.com/life/botany/question439.htm
• Stanford University. "Red Cabbage Lab: Acids and Bases." web.stanford.edu/~ajspakow/downloads/outreach/ph-student-9-30-09.pdf
• How to Make a Red Cabbage pH Indicator
• Poinsettia pH Paper
• Fried Green Egg Food Science Project
• Acids and Bases Lesson Plan
• Litmus Paper and the Litmus Test
• Edible pH Indicators Color Chart
• Learn the pH of Common Chemicals
• How to Do Chromatography with Candy and Coffee Filters
• Home and Garden pH Indicators
• Top Chemistry Projects for Bored Kids
• Color Change Chemistry Experiments
• Definition and Examples of Acid-Base Indicator
• Get Bismuth Metal from Pepto-Bismol Antacid Tablets
• How to Do Paper Chromatography With Leaves
• Science Projects Photo Gallery
• Litmus Paper Definition

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curriculum for educators everywhere!

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• TeachEngineering
• Red Cabbage Chemistry

Hands-on Activity Red Cabbage Chemistry

Grade Level: 8 (7-9)

Time Required: 45 minutes

Expendable Cost/Group: US $5.00

Group Size: 3

Activity Dependency: Introduction to Environmental Engineering Introduction to Water Chemistry

Subject Areas: Chemistry, Measurement, Physical Science, Problem Solving, Reasoning and Proof, Science and Technology

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An important consideration for environmental and chemical engineers is pH. The pH of different liquids and solutions, particularly the pH of bodies of water, are important in describing the behavior of different minerals and chemicals. For example, with increasing acidic pH values, water begins to cause harm and destruction of ecosystems and minerals, such as dissolving the calcium carbonate shells of mollusks, or making ecosystems unlivable for plants and animals.

After this activity, students should be able to:

• Define acidity and basicity and how they relate to different liquids.
• Relate the importance of pH to environmental systems such as lakes, rivers and oceans, as well as environmental engineering concerns.
• Explain how pH, acids and bases are important factors in natural systems, such as the human body.

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Each group needs:

• eight 5-ounce (~148 ml) paper cups, containing vinegar, lemon juice, milk, 7-Up or Sprite, baking soda, Windex, and red cabbage juice indicator (prepared by teacher, see below), respectively
• 7 pH indicator strips
• Red Cabbage Chemistry Worksheet , one per student

For the teacher (to prepare group materials; instructions in Procedure section):

• 2 red cabbages
• large pot, water, stove, strainer
• pitcher or jug, to hold red cabbage indicator from pot
• marker, to label paper cups
• tablespoon, to measure baking soda
• extra 5-ounce paper cups, to double-up on the Windex cups
• the seven test items (as listed above), enough for all teams

Have students complete the Introduction to Water Chemistry lesson before conducting this activity.

Red cabbage juice contains a natural pH indicator that changes colors depending on the acidity of the solution. The pigment in red cabbage that causes the red color change is called flavin (an anthocyanin).

Flavin is a water-soluble pigment also found in apple skins, plums and grapes. Very acidic solutions turn the indicator a red color, neutral solutions turn the indicator a purple color, and basic solutions turn the indicator a greenish-yellow color.

The pH of a solution expresses the concentration of hydrogen ions (H + ). At a lower pH, more hydrogen ions are in solution, and therefore the solution is acidic. Many reactions in nature involves an increase or decrease in acidity. For example, as CO 2 concentrations in the atmosphere increase, greater amounts are dissolved in the oceans, reacting with H 2 O to form carbonic acid (H 2 CO 3 ). Carbonic acid quickly disassociates into bicarbonate(HCO3 - ) and hydrogen ion (H + ).

Environmental and chemical engineers who focus on water quality, water treatment and water remediation need to measure, monitor and sometimes even adjust the pH of water. For example, in the water treatment process, important chemical reactions are affected by the pH of the water. Through today's activity, we will learn more about the pH of different liquids.

Before the Activity

• Gather materials and make copies of the Red Cabbage Chemistry Worksheet .
• For each group, label eight paper cups: milk, water, baking soda, Windex, soda pop, lemon juice, vinegar, cabbage indicator.

• On the day of the activity, fill each cup halfway (or less) with its respective liquid or powder (a tablespoon of baking soda). Double up on the Windex cup to prevent it leaking through. It does not take much indicator before one can see a color change, so small amounts of the cabbage indicator from its cup will be added to each of the seven cups of other liquids.

With the Students

• Divide the class into groups of three students each.
• Hand out the worksheets.
• Direct student groups to each pour a small amount from the "cabbage indicator" cup into the seven cups of different liquids and a powder. Add just enough indicator until a color change appears. Have students record their observations on the worksheet and rank the test items based on their pH values (1 = lowest pH, 7 = highest pH).
• Then have students use pH-indicator strips to measure and record the pH of the liquids in each cup.
• Have students complete the worksheet questions.
• Conclude by leading a class discussion to compare results and conclusions, and make the connection to real-world applications, as described in the Assessment section.

acid: A solution with a sour-taste and low pH value.

base: A solution with a sweet taste and high pH value.

indicator: A solution that changes colors in the presence of acids and bases to help indicate the pH value.

pH: A scale that measures acidity and basicity.

Pre-Activity Assessment

Lesson Recap & Predictions: As a class, review the concepts presented in the associated lesson that relate to pH. Focus the conversation on topics such as acid rain and acid mine drainage. Have students predict which test liquids they think are acidic and which are basic.

Activity Embedded Assessment

Worksheet: Have students use the Red Cabbage Chemistry Worksheet to record their data and answer questions. Observe their written observations, data and answers to gauge their comprehension.

What's Going On? While students are conducting the lab, walk around and ask them questions to keep them engaged and on task, such as: Are the results from the indicator test what you expected? Why or why not?

Post-Activity Assessment

Wrap-Up Discussion: At lab end, bring students together as a class and ask them the following questions. Make sure everyone understands the answers.

• How did your results from the red cabbage pH indicator compare to the pH indicator strips? What are similarities and/or differences? (Listen to student experiences; answers will vary. From most acidic to most basic, the pH values of the tested items are: lemon juice [2], vinegar [3], soda pop [4], milk [6], pure water [7, neutral], baking soda [9], Windex [11, an ammonia solution].)
• What other acids and bases do we encounter every day? (Listen to student ideas. Example everyday acids and their typical pH values: Battery acid [0], citrus fruit juices [citric acid] such as in lemonade [2-3], tea [4-6], bananas [5], black coffee [5+], rainwater [5-6], shampoo [varies, usually slightly acidic]. Example everyday bases: Egg whites [8], antacids [9-10], soapy water [12], bleach [13], oven cleaner [13], liquid drain cleaner [14]. Oven cleaners are designed to have pH values greater than 12 because the grease, fat and carbon found in ovens are easily dissolved in reaction with extremely alkaline [base] solutions. A range of pH values are found in the human body from highly acidic gastric acids [1] to skin [5.5] to blood [7.4]. Tums ® is a base that is designed to help neutralize stomach acids. See if students want to extend the activity by testing other items of interest.)
• Why is understanding the pH value of liquids important to environmental engineers? (Points to make: Human activity can disturb the natural balance necessary for ecosystems to work. Engineers are focused on preventing and fixing situations that put our natural environment at risk, for example, by the alteration of pH levels from the misuse and overuse of natural resources—acid mine drainage, industrial waste, leaking sewage and fuel tanks, agricultural chemical runoff, dissolved pharmaceuticals, etc. Talk about acid neutralization remediation using bases and make the connection to what students learned in the lab. Engineers also need to know about pH to design tools such as the pH indicator strips.)
• You've heard of "acid rain." Why are we concerned about acid rain? (Answer: The pH of water is generally neutral [7], and rainwater is slightly acidic [5-6], but acid rain is much more acid [2-6] and thus, corrosive. This is not the natural pH of rainwater and it alters the environment for wildlife, trees and plants, and slowly deteriorates buildings and statues. With increasing acidity, water begins to cause harm and destruction of ecosystems, such as slowing the reproduction of fish and other marine life and being too acidic to survive, or dissolving the minerals such as calcium carbonate that form the shells of mollusks.)
• From what you know now, what would happen if we mixed some of our solutions? (If time remains, have students mix solutions they found to be acidic with solutions that they found to be basic to observe any chemical reactions and corresponding color changes. Or, add baking soda to the acidic solutions to neutralize them.)

Double up on the paper cup with the Windex; otherwise, it tends to leak after a few minutes.

Have students test other liquids for their pH values and/or perform this lab activity at home. Consider testing items found in the kitchen, bathroom, laundry and garden.

• For lower grades, conduct the similar Acid (and Base) Rainbows activity, targeted for sixth grade students.

Have students use this equation for each liquid's pH value to determine the concentration of hydrogen ion in each of the seven liquids.

Students are introduced to acids and bases, and the environmental problem of acid rain. Students also conduct a simple experiment to model and discuss the harmful effects of acid rain on our living and non-living environment.

Students learn the basics of acid/base chemistry in a fun, interactive way by studying instances of acid/base chemistry found in popular films such as Harry Potter and the Prisoner of Azkaban and National Treasure. Students learn what acids, bases and indicators are and how they can be used, includi...

Students use a simple pH indicator to measure how much CO2 is produced during respiration, at rest and after exercising. They begin by comparing some common household solutions in order to determine the color change of the indicator.

Students learn about the basic properties of light and how light interacts with objects. They are introduced to the additive and subtractive color systems, and the phenomena of refraction. Students further explore the differences between the additive and subtractive color systems via predictions, ob...

Helmenstine, Anne Marie. Chemistry. Red Cabbage pH Indicator - How to Make Red Cabbage pH Indicator . About.com: Accessed September 15, 2009. http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm

Contributors

Supporting program, acknowledgements.

This curriculum was developed with support from National Science Foundation GK-12 grant number DGE 0538541. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.

Last modified: October 26, 2023

Red Cabbage Chemistry

Learn how to make a red cabbage indicator that will test the acidity or alkalinity of certain liquids.

Print this Experiment

Ahh, the sweet smell of science! This next activity is super smelly, but really cool activity. Plug your nose and get ready to make your own red cabbage indicator that will test the acidity or alkalinity of certain liquids. Everyone loves searching for acids and bases in the kitchen, right?

Experiment Videos

Here's What You'll Need

Red cabbage, clear drinking glasses, white paper, apron or lab coat (cabbage juice can leave nasty stains), test chemicals: vinegar, baking soda, lemon juice, washing soda, laundry detergent, soda pop, and alka-seltzer, adult supervision, let's try it.

Peel off three or four big cabbage leaves and put them in a blender filled one-half full with water. Blend the mixture on high until you have purple cabbage juice.

Pour the purplish cabbage liquid through a strainer to filter out all of the big chunks of cabbage. Save the liquid for the experiments to follow.

Set out three glasses, side by side. Fill each glass three-fourths full with cabbage juice.

Add a little vinegar to the first glass of cabbage juice. Stir with a spoon and notice the color change to red, which indicates that vinegar is classified as an acid. All acids will turn red when mixed with cabbage juice.

In the second glass, add a teaspoon of washing soda or laundry detergent. Notice how the liquid turns green, indicating that this chemical is a base.

Keep the two glasses of red (acid) and green (base) liquid for future reference. Fill the third glass of purple cabbage juice to show the color of a neutral solution.

How Does It Work

Some substances are classified as either an acid or a base. Think of acids and bases as opposites—acids have a low pH and bases have a high pH. For reference, water (a neutral) has a pH of 7 on a scale of 0–14. Scientists can tell if a substance is an acid or a base by means of an indicator . An indicator is typically a chemical that changes color if it comes in contact with an acid or a base.

As you can see, the purple cabbage juice turns red when it mixes with something acidic and turns green when it mixes with something basic. Red cabbage juice is considered to be an indicator because it shows us something about the chemical composition of other substances.

What is it about cabbage that causes this to happen? Red cabbage contains a water-soluble pigment called anthocyanin that changes color when it is mixed with an acid or a base. The pigment turns red in acidic environments with a pH less than 7 and the pigment turns bluish-green in alkaline (basic) environments with a pH greater than 7.

Red cabbage is just one of many indicators that are available to scientists. Some indicators start out colorless and turn blue or pink, for example, when they mix with a base. If there is no color change at all, the substance that you are testing is probably neutral, just like water.

Take It Further

You can also make your own pH indicator strips, like you see lifeguards using to test the pH of pool water. To do this, soak some coffee filter paper in concentrated cabbage juice. Remove the paper from the cabbage juice and hang it up by a clothespin to dry. Cut the dried paper into thin strips. Dip the strips into various liquids to test their pH. The redder the strip turns, the more acidic the liquid is. The greener the strip turns, the more basic the liquid is. If it stays purple, you guessed it, the substance you’re testing is probably neutral.

Science Fair Connection

Preforming the Red Cabbage Chemistry experiment is pretty cool, but it isn’t a science fair project. You can create a science fair project by identifying a variable, or something that changes, in this experiment. Let’s take a look at some of the variable options that might work:

• Fill additional glasses with purple cabbage juice. Look around your home. Think of other household chemicals that you use daily (shampoo, glass cleaner, dish soap, hand soap, salt, ammonia, etc.) Try adding a small amount of each household chemical to your cabbage juice. Note the color change to determine if the chemical is an acid (red) or a base (green).
• Fill additional glasses with purple cabbage juice. Look around your kitchen. Think of other household liquids that you use consume (soda, milk, orange juice, coffee, lemonade, etc.) Try adding a small amount of each liquid to your cabbage juice. Note the color change to determine if the chemical is an acid (red) or a base (green).

These are just a couple of ideas, but you aren’t limited to those! Try coming up with different ideas of variables and give them a try. Remember, you can only change one thing at a time. If you are testing a different household chemicals, make sure that the other factors remain the same!

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Science At Play: Red Cabbage Juice Indicator

• Andrew Fotta
• August 12, 2020

Join Andrew and Samantha for another Kitchen Science experiment you can try at home. Use red cabbage to create a pH indicator. It can tell you whether something is an acid or a base, as well as how acidic or basic it is, based on how much the color changes. Use your new pH indicator to see how acidic and basic different items around your house are. Keep reading to learn all the details. 

Materials to Collect

• 1 head of red cabbage
• Sharp knife
• Pot to boil water in (or blender)
• Strainer or colander
• clear cups or glasses
• household liquids to test (vinegar, baking soda, juices, soaps, bleach, ammonia, and anything else you want!)
• Something to stir with

 Make your Indicator!

• Take your red cabbage and have an adult help you cut off about 2-3 cups (the amount doesn’t need to be exact, the more cabbage, the more indicator you will get).
• Have an adult boil a pot of water and place the cabbage pieces in. Bring the water back to a boil for a couple minutes. Turn heat off and let sit for at least 10 minutes. Again, there’s no magic number, you just want the water to be a reddish-purple color. (You can also place the cabbage in a blender with water).
• Strain the water out into a glass bowl and let cool.
• Once it has cooled, pour some into clear cups or glasses and add different liquids to test. 
• Gently stir or swirl the solution and see what happens!

(Be careful about mixing household cleaners together, as some combinations may produce harmful fumes. Only test one substance at a time.)

What is the Science? 

What you have made is called a pH indicator. It can tell you whether something is an acid or a base, as well as how acidic or basic it is, based on how much the color changes. Think of acids and bases as opposites—acids have a low pH and bases have a high pH. For reference, water (which is neutral), has a pH of 7 on a scale of 0–14. An indicator is typically a chemical that changes color if it comes in contact with an acid or a base.

As you can see, the purple cabbage juice turns red when it mixes with something acidic and turns green when it mixes with something basic. Red cabbage juice is considered to be an indicator because it shows us something about the chemical composition of other substances.

What is it about cabbage that causes this to happen? Red cabbage contains a water-soluble pigment called anthocyanin that changes color when it is mixed with an acid or a base. The pigment turns red in acidic environments with a pH less than 7 and the pigment turns bluish-green in alkaline (basic), environments with a pH greater than 7.

Red cabbage is just one of many indicators that are available to scientists. Some indicators start out colorless and turn different colors when they mix with an acid or a base. If there is no color change at all, the substance that you are testing is probably neutral, just like water.

Use this chart to help you figure out how acidic or basic your test liquids are:

Want to know more about what exactly pH is? look here:

https://sciencetrends.com/what-does-ph-stand-for-and-mean/

  Ask Your Young Scientists

• Do all the acids or bases change the indicator the same color? What do you think this means?
• Does adding a larger quantity of an acid or base change the color more?
• Do you see any patterns in what the acids or bases are used for?

More to Explore

• Make your own indicator strips by soaking coffee filters cut into strips in the red cabbage juice, then letting them dry completely. Once dry, you can dip them into a liquid to see its pH. 
• After adding an acid, can you get the indicator to change back to its original color? What do you think you would have to add?

We want to see what you try at home. Share your experiments with us on social media by using the #ScienceAtPlay and tagging @CTScienceCenter.

Andrew Fotta is a STEM educator at the Connecticut Science Center. He has currently holds a CT teaching certification for grades K-6, and has spent time in the classroom in nearly all grades, and taught middle school science. In addition to teaching classes for the Science Center, Andrew is also part of a team of educators currently creating new programs aligned with the new Next Generation Science Standards for grades PreK-9. Andrew is an avid photographer, who enjoys blending science and art in his work.

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• Red Cabbage Indicator

Red Cabbage Indicator - Practicals Experiment

Indicators are chemical compounds that can be added to a solution to determine whether the solution is acidic, basic or neutral. A red cabbage pH indicator is a purple-coloured solution that is often found in homes and can be used to prepare a solution that is used to test whether substances are acid or base.

The cabbage contains a pigment molecule called flavin or anthocyanin which changes the colour depending on the acidity of the solution. Now let’s conduct a red cabbage indicator experiment to observe the results.

To determine the chemicals are acids or bases.

Acids are sour in taste, Eg: vinegar  ( Ethanoic acid ) and lemons ( Citric acid ).

Alkalis are substances chemicals that react with acids and neutralize them. Eg: Soap and washing powder are alkaline.

Acids and alkalis are found in a number of substances, Some are edible and can be found in foods. Some are very strong and can be harmful, such as the acid used in car batteries and the alkali used in oven cleaners.

Apparatus Required

Red cabbage leaves

Lemon juice

baking soda

Glass jars of the same size

Cut the cabbage leaves into small pieces, boil a cup of water separately.

Place the cabbage pieces in a bowl and pour the water into the bowl. Keep it for several minutes so that the cabbage pieces get soaked.

Take glass jars and place them apart. Pour every chemical (lemon juice, vinegar, detergent, and soda) in each jar.

Now to determine whether the substance is a base or an acid pour the cabbage juice indicator into each jar. If the mixture turns pink or red the chemical is an acid and if it turns blue or green the chemical is a base.

The Red Cabbage pH Scale

Different red cabbage ph levels and the colours obtained during the red cabbage juice indicator are given below:

(Image to be added soon)

Did You Know?

Apart from the solution, pH paper strips can also be made using red cabbage. We can use filter paper and dip it in the concentrated solution obtained from red cabbage. Soak it for some time and then take the paper to dry it. Once it is dried, cut the paper into small strips and they are ready to be used. Pour a drop of liquid on the test strip and check the colour obtained. The strip also turns red or green depending on whether it is acidic or basic.

FAQs on Red Cabbage Indicator

1. What is the pH of red cabbage juice?

The pH of red cabbage is around 7. It contains a chemical called anthocyanin which changes colour depending on the acidity of its environment.

2. Is red cabbage a natural indicator?

Red cabbage juice contains a natural pH indicator that changes colours depending on the acidity of the solution. The pigment in red cabbage that causes the red colour change is called flavin.

3. How long can we keep the red cabbage indicator?

Unused red cabbage indicator solution can be stored in a stoppered flask and refrigerated for one week.

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Science with Mike

Acid and Bases pH Experiment (w/ Red Cabbage Indicator)

Episode 2 | 4m 36s

A crash course on the basic differences between acids and bases, complete with a classroom-friendly experiment demonstrating the strength of such compounds using a red cabbage pH indicator. Thank you again, Professor Canestaro, for bringing us such entertaining, hands-on lab experiments!

Aired: 11/08/17

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