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Red Cabbage pH

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Red Cabbage pH

Postby MichaelXY » Wed Feb 13, 2008 1:32 am

I was just curious if anyone has made red cabbage pH indicator. Key word here is made, not used. I was curious about the procedure for making this colorful concoction. Do you need Distilled H2O? How much cabbage do you need? Is there any grams of cabbage per liter issues?
I have a Pre-K teacher friend who wants to appear as Ms. Wizard to her students.

Thanks
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Re: Red Cabbage pH

Postby mcar » Wed Feb 13, 2008 2:27 am

We had tried using a red cabbage extract as a pH indicator once. We actually referred to Janice VanCleave's A+ Projects in Chemistry. Although there was no exact quantity of how much cabbage and distilled water used. Hope that it would help.
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Postby mith » Wed Feb 13, 2008 3:08 am

If you need it to be more concentrated, just boil off excess water?
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Postby MichaelXY » Wed Feb 13, 2008 6:27 am

So I assume a higher cabbage to H2O ratio is better.

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Postby mith » Wed Feb 13, 2008 6:47 am

Well, here's what I would do, make a concentrated solution and then try diluting it to test it's effectiveness. Given that your friend is a teacher, probably means she'll have to deal with spills and dispensing to quite a large number of kids.
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Re: Red Cabbage pH

Postby MichaelXY » Thu Feb 14, 2008 2:09 am

Thanks for the replies. I decided to write a lesson plan for the teacher to use for her demonstration. I would like your opinion on it. Did I miss anything, or make errors. I really am not concerned about grammer,so save it on that point. Thanks
edited----------------------------------------------------------
Shoot, I can't add .pdf or .doc, I am getting a can't add pdf extension message, so never mind this post.
re-edit--------------------------------------------------------------
Since I cant post a doc file I will just do a copy paste. My formatting will be lost though:(

Acid Rain

Introduction: The purpose of this paper is to present the subject of chemistry and how it plays a vital role on our planet to pre kindergarten students. It is the intention that this material will be provided in such a way as to enlighten, but not be over complicated for the projected age group. Teachers are suggested to tailor this material as appropriate for intended audience. The goal is to teach the impact and importance that acid rain presents to the planet.
Remember, we are thinking green.

Discussion: Everything on this planet, from the air we breathe, the smallest grain of sand, to the entire planet is made up of tiny particles that we can’t see, called atoms. Just like all the children in this classroom, all atoms have a name, like Carbon, Hydrogen, Oxygen, and even Gold and Silver. Yes! Gold is made of gold atoms. We can see the gold because it is made of millions or even billions of atoms. Billions is a really big number, a string wrapped around the earth would require billions of inches of string.
Now let’s get back to atoms of gold. When one atom of gold is mixed with another atom of gold we get what is called a molecule. Those are fancy names, but all you need to know is that atoms and molecules make up the things we see, feel, and even some things like air.
Atoms and molecules are all around us—oops I just bumped into some air molecules—and some molecules in the air are not wanted. A car burns gas to make it go, but something happens when this gas is burned. It makes pollution, yuck! All cars have an exhaust pipe, and many harmful molecules come out of this pipe. Some we can see as black or white smoke, others we can’t see, but they are there. Of the gases that come out from the cars tailpipe, one is called carbon dioxide (I know big word, but the kids can handle it).
Why do we Care?
When carbon dioxide mixes with water, such as rain in our sky, it produces a thing called an acid. This is a weak acid, but it is still not good. Acids can burn eyes, skin, lungs, and even corrode metal. Rain mixed with acid is acid rain.
Demonstration:
Now the fun part begins. You need a solution of red cabbage. Put a several drops into a container of water, it may turn pink. Now take some vinegar and add a few drops and mix, the solution should turn yellow. If not, add some more vinegar. Explain to the class that you just add some acid to the water, and that is why it changed colors. Now take another container of water, add a few drops of red cabbage solution—and here is the cool part—take a straw, and blow bubbles into the water solution. If all went well, the solution should turn yellow. Since humans exhale carbon dioxide, you just proved that CO2 is an acid.
Conclusion:
The main goal is to teach how molecules that we can not see do exist, and do have an affect on our planet. Discuss how car usage affects the air we breathe. Discuss ways to reduce acid rain, like car pooling, cutting back on energy usage etc.
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Re: Red Cabbage pH

Postby mcar » Thu Feb 14, 2008 1:51 pm

MichaelXY wrote:
Thanks for the replies. I decided to write a lesson plan for the teacher to use for her demonstration.

Shouldn't your teacher friend be the one to write her lesson plan? For sure that she already know the ways in writing a lesson plan and its contents as well.

What is important here is that your objectives are clear and each objective (covering the domains of learning: cognitive, affective and psychomotor) should be at least evident by the response or action of the pupils as they learn the topic. I'm seeing here that the three domains of learning are covered. Another, a very good motivation will get the pupil's interests and attention.
Motivations may somehow get them amazed.

As I see that big words could be handled by some kids, however at their young age, chemical words may still appear complicated to them. The idea here is that the material should be at least within the learning ability and preparedness of their mind.

I do hope that the demonstration of your friend will go well and again, good luck.
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