If you love the idea of mixing up chemicals and dream of having your own mad science lab one day, this one is for you. You are going to mix up each solid with each liquid in a chemical matrix.


In a university class, one of the first things you learn in chemistry is the difference between physical and chemical changes. An example of a physical change happens when you change the shape of an object, like wadding up a piece of paper. If you light the paper wad on fire, you now have a chemical change. You are rearranging the atoms that used to be the molecules that made up the paper into other molecules, such as carbon monoxide, carbon dioxide, ash, and so forth.


How can you tell if you have a chemical change? If something changes color, gives off light (such as the light sticks used around Halloween), or absorbs heat (gets cold) or produces heat (gets warm), it’s a chemical change.


What about physical changes? Some examples of physical changes include tearing cloth, rolling dough, stretching rubber bands, eating a banana, or blowing bubbles.


About this experiment: Your solutions will turn red, orange, yellow, green, blue, purple, hot, cold, bubbling, foaming, rock hard, oozy, and slimy, and they’ll crystallize and gel — depending on what you put in and how much!


This is the one set of chemicals that you can mix together without worrying about any lethal gases.  I do recommend doing this OUTSIDE, as the alcohol and peroxide vapors can irritate you. Always have goggles on and gloves on your hands, and a hose handy in case of spills. Although these chemicals are not harmful to your skin, they can cause your skin to dry out and itch. Wear gloves (latex or similar) and eye protection (safety goggles), and if you’re not sure about an experiment or chemical, just don’t do it. (Skip the peroxide and cold pack if you have small kids.)


Materials:
• sodium tetraborate (borax, a laundry whitener)
• sodium bicarbonate (baking soda)
• sodium carbonate (washing soda)
• calcium chloride (also known as “DriEz” or “Ice Melt”)
• ammonium nitrate (single-use disposable cold pack)
• isopropyl rubbing alcohol
• hydrogen peroxide
• acetic acid (distilled white vinegar)
• water
• liquid dish soap (add to water)
• muffin tin or disposable cups
• popsicle sticks for stirring and mixing
• tablecloths (one for the table, another for the floor)
• head of red cabbage (indicator)


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Download Student Worksheet & Exercises


Step 1: Cover your kitchen table with a plastic tablecloth (and possibly the floor). Place your chemicals on the table. A set of muffin cups make for an excellent chemistry experiment lab. (Alternatively, you can use empty plastic ice cube trays.) You will mix in these cups. Leave enough space in the cups for your chemicals to mix and bubble up — don’t fill them all the way when you do your experiments!


Step 2: Set out your liquid chemicals in easy-to-pour containers, such as water bottles (be sure to label them, as they all will look the same): alcohol, hydrogen peroxide, water, acetic acid, and dish soap (mixed with water). Set out small bowls (or zipper bags if you’re doing this with a crowd) of the powders with the tops of your water bottles as scoopers. The small scoopers regulate the amounts you need for a muffin-sized reaction. Label the powders, as they all look the same.


Step 3: Prepare the indicator by coarsely chopping the head of red cabbage and boiling the pieces for five minutes in a pot full of water. Carefully strain out all the pieces with a fine-mesh strainer; the reserved liquid is your indicator (it should be blue or purple).


When you add this indicator to different substances, you will see a color range: hot pink, tangerine orange, sunshine yellow, emerald green, ocean blue, velvet purple, and everything in between. Test out the indicator by adding drops of cabbage juice to something acidic, such as lemon juice, and see how different the color is when you add indicator to a base, such as baking soda mixed with water.


Have your indicator in a bottle by itself. An old soy sauce bottle with a built-in regulator that keeps the pouring to a drip is perfect. You can also use a bowl with a bulb syringe, but cross-contamination could be a problem. Or it could not be — depending on whether you want the kids to see the effects of cross-contamination during their experiments. (The indicator bowl will continually turn different colors throughout the experiment.)


Step 4: Start mixing it up! When I teach this class, I let them have at all the chemicals at once (even the indicator), and of course, this leads to a chaotic mix of everything. When the chaos settles down, and they start asking good questions, I reveal a second batch of chemicals they can use. (I have two identical sets of chemicals, knowing that the first set will get used up very quickly.)


Step 5: After the initial burst of enthusiasm, your kids will instinctively start asking better questions. They will want to know why their green goo is creeping onto the floor while someone else’s just bubbled up hot pink, seemingly mixed from the same stuff. Give them a chance to figure out a more systematic approach, and ask if they need help before you jump in to assist.


What’s happening with the indicator? An indicator is a compound that changes color when you dip it in different things, such as vinegar, alcohol, milk, or baking soda mixed with water. There are several extracts you can use from different substances. You’ll find that different indicators are affected differently by acids and bases. Some change color only with an acid, or only with a base. Turmeric, for example, is good only for bases. (You can prepare a turmeric indicator by mixing 1 teaspoon turmeric with 1 cup rubbing alcohol.)


Why does red cabbage work? Red cabbage juice has anthocyanin, which makes it an excellent indicator for these experiments. Anthocyanin is what gives leaves, stems, fruits, and flowers their colors. (Did you know that certain flowers, such as hydrangeas, are blue in acidic soil but turn pink when transplanted to a basic soil?) You’ll need to get the anthocyanin out of the cabbage and into a more useful form so you can use it as a liquid indicator.


Tip for Testing Chemical Reactions: Periodically hold your hand under the muffin cups to test the temperature. If it feels hot, it’s an exothermic reaction (giving off energy in the form of heat, light, explosions …). The chemical-bond energy is converted to thermal energy (heat) in these experiments. If it feels cold, you’ve made an endothermic reaction (absorbing energy, where the heat from the mixture converts to bond energy). Sometimes you’ll find that your mixture is so cold that it condenses the water outside the container (like water drops on the outside of an ice-cold glass of water on a hot day).


Variations for the Indicator: Red cabbage isn’t the only game in town. You can make an indicator out of many other substances, too. Here’s how to prepare different indicators:
• Cut the substance into smaller pieces. Boil the chopped substance for five minutes. Strain out the pieces and reserve the juice. Cap the juice (indicator) in a water bottle, and you’re ready to go.
• What different substances can you use? We’ve had the best luck with red cabbage, blueberries, red and green grapes, beets, cherries, and turmeric. You can make indicator paper strips using paper towels or coffee filters. Just soak the paper in the indicator, remove and let dry. When you’re ready to use one, dip it in partway so you can see the color change and compare it to the color it started out with.
• Use the indicator both before and after you mix up chemicals. You will be surprised and dazzled by the results!


Teaching Tips: You can make this lab more advanced by adding a postage scale (to measure the solids in exact measurements), small beakers and pipettes for the liquid measurements, and data sheets to record temperature, reactivity, and acid/base indicator levels. (Hint: Make the data sheet like a matrix, to be sure you get all the possible combinations.)


For the student: Your mission is to mix up solutions that:
• Generate heat (exothermic)
• Get ice-cold on their own (endothermic)
• Crystallize
• Are self-gelling
• Bubble up and spit
• Ooze creepy concoctions
• Are the most impressive (the ooohhhh-aaahhhhh factor).


For the parent: Your mission is to:
• Make sure everything in reach is covered with plastic tablecloths, drop cloths, or tarps
• Open all the windows and turn on the fans (or just do this experiment outside near the hose)
• Keep all small children and pets away
• Slap on a pair of rubber gloves
• Encourage the kids to try it and test it
• Remember that there are no such things as mistakes, only learning opportunities. (Don’t forget that we usually learn more from mistakes than we do when we’re successful!)


For the truly exceptional parent: Your mission is also to:
• Secretly get an identical second set of chemicals from the grocery store (see shopping list above) and hide them in a bin nearby
• Have all the chemicals out and ready for the kids to use
• Be sure the kids know your rules before you let them loose (no eating, running, or horseplay; all goggles must stay on; etc.)
• Have a bin full of water nearby for washing up
• Let the kids loose to experiment and play without expectation
• Play with the kids, get into the act (“Wow! It turned green! How did you do that?!” instead of “Well, I’m not going to clean THAT up.”)
• Expect kids to dump everything and mix it all together at the same time without much thought about what they are trying to accomplish
• When their supplies run out, pull out your second bin and smile
• Encourage the kids to try their ideas out
o When they ask, “Will this work?” you can reply
with confidence, “I don’t know — try it!”


Click here to view another version of this experiment: Acids & Bases.
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Comments

29 Responses to “Chemical Matrix of Acids & Bases”

  1. If you stuck with the chemicals we listed here, yes the trash or toilet are safe ways to dispose of them.

  2. Jami Bustamante says:

    What is a safe way to dispose of all the end result chemicals? Is it safe to pour in sink or flush down toilet?

  3. There’s a video on how to do it on this page – did you find it? You simply cut up a red cabbage, put it in a blender with enough water to cover, blend well, then strain out the solids. The juice is ready to go!

  4. Iram Memon says:

    Hi, how do you make the red cabbage juice?

  5. Yes, you can use different chemicals with this experiment (just stick to the list and delete the ones you don’t have).

  6. Christie Laing says:

    Can anything be substituted for borax or icemelt?

  7. All you do is put the red cabbage chunks into a blender with some water, whirl it around, and strain out the pulp to get the cabbage juice I used in the video. Hope this helps!

    Aurora

  8. Tracy Turissini says:

    We did this experiment (from the DVD’s). And my only issue with it is that you had red cabbage juice… and we were told to get a head of red cabbage…. I didn’t see or find what to do with our head of red cabbage. So we just tore chunks and tossed it in the cups, which of course didn’t work. The kids were still thrilled but the colors weren’t there.

  9. My kids are having a blast doing this before our camping trip! They are being extremely curious and creative. They’re starting to make predictions before they mix new things. Thank you!

  10. Purple (or red) cabbage, when prepared, is purple. That purple color is not an indicator itself that the cabbage solution is neutral. The solution is actually slightly acidic. Preparation of the solution distills out Anthocyanin molecules that will change their color depending upon the pH of the test solutions. This experiment will tell you whether a substance is an acid or base as compared to whatever low acidic level your cabbage juice contains. To get the true pH of the cabbage juice, you’ll need to do a litmus test on it. Something more acidic than cabbage juice will turn pink, and something basic will turn green.

  11. Connie de Freudiger says:

    Can you please explain. I understand that when purple cabbage is mixed with vinegar it turns pink to show that it is an acid. I thought that purple cabbage with water stays purple and shows that it is neutral and a base will be green.

  12. Christina Severinghaus says:

    Hello
    We did this experiment not once but twice in the last week and our boys had a lot of fun. We invited a few friends over to help mixing, stirring and observing.
    Like the comment above, our mixture with hydrogen perioxide faded, not right away but within a few minutes. We even tried to pour in more cabbage juice, nice and dark, and then a few minutes later, almost clear with a tint of pink….

    After we did all the combinations, the kids made their own mixtures – a lot of fun and we now have some strange looking substances in our garage… some of these combinations created solids that when drained through coffee filter turned malleable, our son rolled some into a ball and the next day it was dry, hard and fun to play with!
    Thank you for yet another great experiment.
    Christina

  13. Solids exist as either a crystal (a solid whose atoms are arranged in a specific shape) or as an amorphous solid (matter that has solidified without a specific or shape). Metals are amorphous solids and can easily be observed solidifying from their liquid, molten state. Metals conform to the shape of whatever container they cool in. Crystals are solids as well, but they form differently. Crystals form into a specific, identifiable shape, paying no attention to the space they are growing in, whether they are quartz crystals or salt crystals. Crystals can be formed in different sizes, but each crystal will look the same. So, crystalline solids form into specific shapes and amorphous solids form into whatever the shape of the container they are cooling in.

  14. When atoms arrange in a certain pattern crystals are formed; that’s how all solids form. How can we explain to a student the difference between the formation of a crystal and a solid or the difference between a crystal and a solid. We can form crystals from any soluble solid. Insoluble solid we can’t call a crystal. How can it be explained?

  15. Jessie Lin says:

    We did this experiment today. It worked really great. We can see pink, yellow, green, blue, brown and purple
    colors. It’s so amazing. We tried vinegar, alcohol and borax, antacid, laundry powder, dish
    detergent, AJAX, shampoo, hand soap etc.. Our hand soap is more of neutral and shampoo is acidic
    so we have to rinse our hair thoroughly. We also saw that some of them are foaming or bubbling when we
    add vinegar in. Thanks, Aurora.

    Jessie, Esther (11) Samuel (10) and Sarah (2)

  16. Sodium carbonate, Na2CO3, releases more heat when dissolved in water. It’s called the heat of solution. It is an exothermic reaction so the products (the hydrated ions) have a lower energy content than the initial compound, resulting in the release of energy in the form of heat to the water.

    Sodium bicarbonate, NaHCO3, releases less heat than the above carbonate. Many polyatomic ions are given the name prefix “bi” when attached to a polyatomic ion (an ion with more than one atom).
    Sulfate, SO2-2 (the -2 is an exponent and indicates the charge on the ion)
    Bisulfate,HSO4-1

    Sulfite, SO3-2
    Bisulfite, HSO3-1

  17. The red cabbage extract indicates not only whether your substance was an acid (vinegar) or a base (ammonia) but also how strong of an acid or base it is. Although this will vary a bit with cabbage, the colors and approximate pH values are red (pH=2), purple (pH=4), violet (pH=6), blue (pH=8), blue-green (pH=10), green (pH=12). When you get a pH value below 7, this means that your substance is acidic. The smaller the number, the more acidic it is. A pH value higher than 7 means that a substance is basic, and the larger the number, the more basic it is. Does that help?

  18. Debbie McDonald says:

    What is it in sodium carbonate that makes the solution warm versus sodium bicarbonate?(What does the “bi” take away that causes the heat reaction?)

  19. Debbie McDonald says:

    We just finished the chemical matrix. What does all the green color indicate?

  20. Some pH strips don’t change as dramatically as others, depending on what kind you’re using and what you’re testing. You can make your own pH strips using the cabbage juice and paper coffee filters – just dip in the juice and let dry. Instant pH strips!

  21. Deanna Betts says:

    We used ph strips and were a bit disappointed– didn’t change colors as much as the cabbage juice would so we are going to try with the juice next time.

  22. Anthocyanins are water-soluble dyes that change color with pH, and can be found in plant leaves, stems, and flowers. When you add anthocyanins to hydrogen peroxide, the peroxide starts to decompose the anythocyanin. Depending on the strength of the two, this will happen faster or slower.

    You can use sour cherry juice, strawberry juice, or pomegranate juice as indicators in place of the red cabbage juice, as these hold up a lot better to the H2O2.

    The reason we have you test hydrogen peroxide (and rubbing alcohol) is that they don’t change as most people expect them to… which is great for honing your observation skills!

  23. Shari Linsley says:

    Just the ones in the peroxide, everything else had beautiful colors!

  24. Hmmm… sounds like you did the experiment right, but just found different results than we showed in the video. Science is like that sometimes! I noticed in the photo that you have colors in the cups. Did all the colors fade after a few minutes after snapping the photo, or just the ones with the H2O2 in it?

    (By the way, great job with Sandia labs! That’s one of the places I was going to work at after graduating from college – they have such AWESOME projects there, even if their name means’ watermelon’!)

  25. Shari Linsley says:

    For liquids we used water, soap, vinegar, alcohol and hydrogen peroxide. The cabbage juice was deep dark purple, almost to the point of black. All of the other liquids held their color and we had a beautiful rainbow display. I e-mailed a pic to you. If you look at the front row, you with notice all of the cups are clear. That is the peroxide row.

    The solids were calcium chloride, sodium bicarb, sodium carb, ammonium nitrate and citric acid. We didn’t dilute anything except the soap solution which we added distilled water to.

  26. What was the original color of your cabbage juice before you added it? Sometimes if your water used in the cabbage juice is already acidic and you add it to a base, it’ll cancel out and turn to a neutral pH color (NOT clear, though!). Also, the more diluted your cabbage juice is, the less color you’ll see when added to your other solutions. You can test it out by adding it to ammonia (which will turn it green/blue) or to distilled white vinegar (which turns it pink). The color should stick around for at least a half hour, maybe having a color change near the end. Tell me more about what you added your cabbage juice to… was it diluted as well?

  27. Shari Linsley says:

    My 7 year old son did this experiment today for our homeschool group. When we put the cabbage juice in the hydrogen peroxide the color faded after a few minutes. We tried adding more with the same result. We are wondering why? Does the peroxide neutralize the anthcyanin or is there something else at work? None of the sample cups held color either. They all reverted to clear or white within a few minutes.

  28. Oops – that was a typo. You’ll find the shopping list ABOVE, not below that text. Sorry about that!

  29. Stephen Chisholm says:

    Where would I find: “Secretly get an identical second set of chemicals from the grocery store (shopping list follows) ….aka the shopping list? Thanks!