Positively pH Explained

The last experiment we did was on testing the pH of common household items. First off, we hope you had fun. This lab is a wonderful learning experience and it captures your attention with the many different colors. With that, lets get started on understanding this lab!

pH is considered a chemical property. If you haven't learned about those, there are two properties: Chemical and Physical. Physical properties are things such as color, taste, and smell. Chemical properties are ones like pH, boiling point and melting point.

Physical Properties do not change the chemical make up of something.
Chemical Properties do change the chemical make up.

pH is a way to measure how acidic or basic a chemical, compound or material is. Acids have a lower number on the pH scale while bases have higher numbers. The number seven is neutral. A common neurtal substance is... water!

Something to remember, the pH scale is logorithmic. This means that the values are 10 time different than each other. For example: A pH of 2 is 10 times more acidic than a pH of 3. However it is 100 times more acidic than a pH of 4. Why? Because between 2 and 3 is an amount of 10 and between 3 and 4 is another amount of 10. To find how much more acidic 2 is than 4 you multiply the two sets of ten.

So 2 is 10x more acidic than 3.
2 is 100x more acidic (10 times 10) than 4.
2 is 1000x more acidic (10 times 10 times 10) than 5.

Scale for Litmus Paper

There are different ways the pH level of something can be measured. The most common way in a science lab is to use litmus paper.

Litmus paper changes color based on the acidity or alkalinity of a substance.
Acidity: How acidic a substance is, the more acidic the lower the number.
Alkalinity: How basic a substance is, the more basic the higher the number.

Normally there are two colors of litmus paper, red and blue. Each color tests for something different. Red litmus paper checks for basic solutions and blue litmus paper checks for acidic.
A handy way to remember which paper to use:


Red turns Blue if it is Basic.
Blue turns Red it is it Acidic.

For this experiment we used a solution made from red cabbage, so the colors for the ranges of pH are different than litmus.
Basic is Yellow.
Acidic is Pink.
Neutral is Blue.
(Neutral is blue because the cabbage juice is a blue color. )

So how does cabbage juice work to determine whether something is acidic or basic?

Ideal Red Cabbage Colors

Cabbage juice is a neutral substance so it is good for testing the pH of a substance. The reason a red cabbage is the purple color is because of something called a flavin, this is a water soluble pigment. This pigment changes colors in different pH levels. The reason for this change is because of hydrogen.

The indicator changes colors because it detects the ratio of hydroxide to hydronium ions.
Hydroxide: Negatively charged, anion made of one hydrogen and one oxygen. OH-
Hydronium: Positively charged, cation made of three hydrogen and one oxygen. H30+

When something is acidic there are more hydronium ions than hydroxide.
When something is basic there are more hydroxide ions than hydronium.
When something is neutral (like water or red cabbage juice) the amounts are equal.

Simple things like lemons are acidic and we know this because of their sour and sharp taste. Things that are basic are often used as cleaning supplies because they take away protons, or make things negatively charged. Basic substances have a soapy feel when on your hands, common laundry soap is basic.

Lemon, and citrus is the iconic 'fresh scent'

WARNING: When working in the lab it is dangerous to touch acids and bases (especially strong ones) these are dangerous.

Some Lovely Links: These links also tell how to do this experiment. It's common, simple and great!
-http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p013.shtml
-http://www.stanford.edu/~ajspakow/downloads/outreach/ph-student-9-30-09.pdf
-http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm
-http://web.jjay.cuny.edu/~acarpi/NSC/7-ph.htm

Please Note: Red Cabbage can have a very strong odor, one that some do not enjoy. Thankfully science can help with this. Over at Spangler Science (lots of supplies!) they have Jiffy Juice, this stuff is great! It is a condensed, power version of Red Cabbage and is odorless! So if you plan on doing this experiment more than once or need a lot of it (especially for schools) this stuff is great. http://www.stevespanglerscience.com/product/1552

Positively pH

In this experiment we are going to show you a very simple and colorful way to learn the difference between the acids and bases in your home!

Materials:
- 1 Head Red Cabbage
- Lemon Juice
- Aspirin
- Vinegar
- Baking Soda
- Epsom Salt
- Tums

1.) Boil the red cabbage until the water turns a blue-ish. (This takes all of the color out of the cabbage)

2.) Let the cabbage juice cool. (This juice is best used fresh, after about 3 days the juice doesn't work as well for this experiment.)


3.) Pour a little bit of cabbage juice into 7 test tubes.


4.) In each test tube add a little of each item. (So in one tube add some aspirin and baking soda in another.)
Leave the last test tube empty as a control.

5.) Compare the colors in each tube. The tube with lemon juice should be a distinct pink color while the baking soda is a blue-green color.

The acids in this experiment will turn a pink or light purple color while the bases will be blue-green.
You can use the red cabbage juice to find out if other things in your house are acidic or basic too! Go try some soap, apple juice, or even a little of that soup you had for dinner!

Dynamic DNA Explained

Deoxyribonucleic Acid

What is it? 
We're sure you've heard of this term; Deoxyribonucleic Acid. No? How about DNA? Well good news, they are the same! DNA is the shortened way of saying the long molecule's name. DNA is known for its double helix shape.
DNA is made up of chemical bases, four to be precise, A, T, C, and G.
A: Adenine
T: Thymine
G: Guanine
C: Cytosine
These chemical compounds match up to one another; A to T and C to G.  This connection is called a base pair. There is another compound, Uracil, that can attach to Adenine, but this is a result of RNA, not DNA.

Double Helix / A-T and G-C pairing

So what is RNA?
We are glad you asked! RNA (Ribonucleic acid) is similar to DNA. They are both nucleic acids but they do different things. DNA is complex and holds secret messages in its makeup. (It's like a chemical spy holding all the secrets about you!) RNA is the only one who can understand these secrets. RNA, in a sense, translates these messages for proteins and other things; it transcribes the message DNA has.

DNA and RNA are also different in shape. Like we said, DNA has a double helix shape; this shape is like a spiral staircase. RNA however is single stranded. RNA has a a couple different shapes, depending on how its base pairs match up.

Shape of RNA/ C-G and A-U pairing

Where is DNA found?
DNA is found inside the nucleus of the cell. The nucleus is a great place for a nucleic acid! The nucleus is inside the cellular membrane of the cell though. How do we break open the microscopic cell membrane and the nucleus? Dish soap! The dish soap breaks apart the molecules of the cell. Both dish soap and the cell membrane have hydrophobic (scared of water) and hydrophilic (loves water) sides.

Why add contact solution, pineapple juice or meat tenderizer?
DNA is folded and cushioned by protein in the cell. The contact solution is acidic and separates the DNA from the protein.

How come the white stuff is DNA?
The DNA is the white, stringy stuff you see in the top layer of alcohol. Alcohol forms a layer on top of the water because it is less dense. Adding salt to the mixture (at the beginning) helps DNA stick together.  But when in water DNA is dissolved. Adding the alcohol brings the DNA 'out of solution', making it undissolved. This is called precipitation.


Further Information:
http://ghr.nlm.nih.gov/handbook/basics/dna
http://www.usask.ca/education/coursework/mcvittiej/bio30unit1/overheads/1.23.htm

Dynamic DNA

This week we're doing an experiment with DNA! Now doesn't that sound exciting? In this lab you will be able to see the very small DNA from a cheek cell or from inside a pea. The procedures for cheek cells and peas are a little different, so make sure you read the instructions.

Pre-Lab:
If you have access to a microscope we suggest you take a look at the cells in your mouth.
1.) Place a drop of iodine on a microscope slide.
2.) Take a toothpick and gently scrape the inside of your cheek.
3.) Place the toothpick in the iodine and swirl.
4.) Start with low power (4x) and look at your cheek cells!
Now that you have a general idea of what your cheek cells look like try this experiment.

Materials
- Spilt Peas, Strawberries or any other DNA source (if not using cheek cells)
- Blender
- Salt
- Water
- Measuring cups
- Test tubes
- Dish soap
- Contact Solution (meat tenderizer or pineapple juice)
- Rubbing alcohol (isopropyl or ethanol)
- Glass stirring rod (wood skewer or Q-tip)

Procedure:
Cheek Cells
1.) Swish salt water in your mouth for 30 seconds. (This is a long time, but you can do it!)
2.) Spit the water into a cup, then pour it into a large test tube.
3.) Add 1 teaspoon of dish soap to the large test tube.
4.) Gently shake the test tube. (If you do this in a beaker or cup, gently stir the cup)
5.) Pour about 1 teaspoon of alcohol into the tube.

The best way to do this is by tilting the test tube and slowing pouring the alcohol.

Ideally there will be a small layer of alcohol above the soapy mixture.

6.) Using the glass stirring rod - twirl in one direction to collect the DNA

Split Peas & Other Foods:

1.) In a blender add and blend on high for 15 seconds:

- 1/2 cup split peas

- 1/8 teaspoon table salt

- 1 cup water

2.) Pour the pea mixture through a strainer (you want the liquid) and let sit for 5-10 minutes

3.) Pour some of the liquid into a test tube

4.) Add 1 teaspoon dish soap to the large test tube

5.) Add some contact solution to the test tube 

(you don't need a lot, a small squirt or a pinch for tenderizer)

6.) Add about 1 teaspoon of alcohol to the test tube

Just like the cheek cells you want a layer of alcohol above the soapy pea mixture

7.) Using the glass stirring rod - twirl in one direction to collect the DNA

You can save this DNA or look at it on a wet slide under a microscope.

To save: Put the DNA in a small test tube or container with some alcohol.

(Pictures for the steps to come)

Further information:
http://www.middleschoolscience.com/microscope.pdf
http://www.pbs.org/wgbh/nova/teachers/activities/pdf/2809_genome_01.pdf
http://www.pbs.org/wgbh/nova/teachers/activities/2809_genome.html
http://learn.genetics.utah.edu/content/labs/extraction/howto/