Thursday, January 13, 2011

Acids and Bases

Introduction to Acids and Bases
Every liquid is either acidic or basic except for water.

Acid comes from the Latin term acere, which means "sour". Acids such as lemon juice and vineger, taste sour, are corrosive to metals, and change litmus (a dye extracted from lichens) red. Another definition for acids is a solution that has an excess of H+ ions.

Bases taste bitter, feel slippery and change litmus blue.  Another definition of a base is a solution that has an excess of OH- ions.   

Scientists use something called the pH scale to measure how acidic or basic a liquid is.  A very strong acid will have a pH of 0.  A very strong basic solution will have a pH of 14.  Water has a pH of 7 because it is neutral.

The table below shows examples of some acids and bases.


[H+]pHExample
Acids1 X 1000HCl
1 x 10-11Stomach acid
1 x 10-22 Lemon juice
1 x 10-33 Vinegar
1 x 10-44Soda
1 x 10-55Rainwater
1 x 10-66Milk
Neutral1 x 10-77Pure water
Bases1 x 10-88Egg whites
1 x 10-99Baking soda
1 x 10-1010Tums® antacid
1 x 10-1111Ammonia
1 x 10-1212Mineral lime - Ca(OH)2
1 x 10-1313 Drano®
1 x 10-1414 NaOH

Taken from http://www.visionlearning.com/library/module_viewer.php?mid=58

Cabbage Juice pH Indicator
Introduction
Red cabbage has a pigment called anthocyanins.  The pigments give it the red/purple color.  Very acidic solutions will turn anthocyanins red and basic solutions will turn anthrocyanins green/yellow.   

Hypothesis
We can determine the pH of a solution by adding it to cabbage juice.  An acidic solution will turn the cabbage juice red and a basic solution will turn the cabbage juice yellow.

Materials
  • red cabbage
    Red Cabbage-chopped
  • 12 glass containers   
  • ammonia
  • lemon juice
  • vinegar
  • antacids
  • seltzer water
  • HCL (hydrocholoric acid)
  • NaOH (sodium hydroxide)
Procedures
1.  Chop the cabbage into small pieces and boil in water for a couple of minutes until the liquid turns a dark purplish color.
2. Pour a little bit of cabbage juice into 6 empty glass containers.
3.  Prepare the 'test' acid/base solutions into 6 glass containers.
4.   Pour a few drops of the test solution into the cabbage juice containers and write down what happens.

Cabbage juice in glass vials


Results
NaOH- turned the cabbage solution yellow

Antacids added to cabbage juice

Ammonia- turned the cabbage solution yellow

Antacids- turned the cabbage solution bluish-green
Seltzer water- nothing happened.
Vinegar- turned the cabbage juice red
Lemon juice- turned the cabbage juice red
HCL- tunred the cabbage juice red
Seltzer water added to cabbage juice






Vinegar and Lemon juice added to cabbage juice









NaOH and Ammonia added to cabbage juice




HCl added to cabbage juice














Conclusion

We found that NaOH, ammonia, and antacids are bases.  Vinegar, lemon juice and HCL are acids.  The seltzer water is neutral.


At the end we mixed a base  (NaOH) and an acid (vinegar) together.  When we poured a little bit of the basic solution into the acid, we got a violet color.  When we poured a little bit more of the basic solution, the violet solution turned green.


Adding NaOH to Vinegar

The result of NaOH added to Vinegar













Adding more NaOH to vinegar

The result of adding a lot of NaOH to Vinegar














Can you explain these results? 


11 comments:

  1. Dear Miriam,

    What an informative post you have put up.
    I like how you back it up with facts too.
    I really did enjoy reading all about Acids and Bases.
    What made your post even more intresting was how you included photograghs which made your post come to life.

    Well done Miriam.
    From AA.

    ReplyDelete
  2. Dear Miriam,
    I love your science post.

    Last year in 2KM we made oobleck with 2KJ's student teacher called Miss Brazer it was so much fun.

    I noticed when you put your hand in softly it was soft but if you put your hand in fast in the oobleck it was hard.

    Here is the link to the oobleck fun post we made. http://2kmblog.globalstudent.org.au/2010/08/06/science-oobleck/.

    Hope you like the oobleck post.

    From Bianca.

    ReplyDelete
  3. @AA and BB,

    I'm glad that you liked my science post. It was really fun doing the experiment but it took a lot of time to write up the post.

    Oobleck looks really cool! I have never heard of it before. Maybe I can try to make it at home too.

    We have a couple of more science experiments that we are planning on doing.

    From,
    ♥Miriam♥

    ReplyDelete
  4. Marsha (Hannah's mom)January 15, 2011 at 12:48 PM

    Dear Miriam,

    What a wonderful post (or should I call it a scientific paper)!
    So well thought out, well written and clearly presented. The photos make it very easy for the reader to follow your presentation. It must have taken you a very long time to put this marvelous post together.

    Reading your post took me back to my school days. Although, I must admit that I was much older than you when I did similar experiments. You are quite a little scientist!

    I Look forward to your future post.

    Love,
    Marsha (Hannah's mom)

    ReplyDelete
  5. Hi Miriam,

    That is an amazing post. How old are you? This writing is so polished and the post is full of interesting facts.

    I am wondering if cabbage water is also neutral because it is an acid-base indicator. Also, I'm wondering if water is always neutral. What about water in a swimming pool?

    I am also wondering if you made the table yourself or if you copied it from somewhere else. It looks like a lot of work to make such a table.

    What a great post!
    @mmeveilleux

    ReplyDelete
  6. Dear Miriam,

    You have done a wonderful post! I learned so much from it. I did not understand it completely at first but when my mom explained it to me it became clearer.

    You must have worked very hard on this and it must have taken you a very long time. I don't think I could have done a post this great without a lot of help from my mom.

    Congratulations on doing such a great scientific experiment and for explaining it so nicely. I hope to do something like that one day!

    Your friend,
    Hannah

    ReplyDelete
  7. Hi Miriam,
    I am very impressed with your posts about acids and bases. You have a lot of information to share. I like the photos of your experiments. Great job!

    Happy blogging,
    Mrs. Pearson
    3rd grade teacher, Iowa

    ReplyDelete
  8. Miriam,

    There's really only one word to describe this post, WOW! Your blog post is amazing. You're such a wonderful writer. If I didn't know any better, I would've thought this was written by somebody much older!

    Keep up the great work!

    Mr. Avery
    Plympton, Massachusetts
    Mr. Avery's Class Blog

    ReplyDelete
  9. Dear Miriam,

    What an impressive post! You did a fantastic job explaining the relationship between pH, acids, and bases.

    When I studied oceanology in high school we always tested the pH of water samples from different locations. I remember that sea water has a slightly higher pH than "neutral" fresh water. I think it is usually between 7.5 - 8.3.

    My favorite thing about your post is all the wonderful pictures. I thought it was very interesting that cabbage juice makes such a pretty purple color. And the blue-green color from the mix of NaOH and vinegar was very cool!

    Thanks for such an interesting post.

    From,
    Mr. Salsich

    ReplyDelete
  10. ♥ ★ ♥ ★ ♥ ★ ♥ ★ ♥ ★ ♥ ★ ♥

    @Hannah,


    I had a wonderful time doing this experiment. I am glad that I have a dad that is a chemist because he brought the chemicals.

    Have you done any experiments at home?


    From,
    Miriam


    ♥ ★ ♥ ★ ♥ ★ ♥ ★ ♥ ★ ♥ ★ ♥

    ReplyDelete
  11. @mmeveilleux,

    Thank you for commenting. I am a third grader in Mrs. Yollis' class. My mom helped me put together the experiment and post. It took along time to write everything that we did and explain it.

    Cabbage juice and pool water is also neutral. I didn't make the table, but borrowed it from another site. The link of the site with the table is on my blog.

    From,
    Miriam

    ReplyDelete

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