Expert: Amy - 2/11/2005

Question
I am in 3rd grade.My mom helped me type this so that you can understand what questions I need answered.I have to turn my project on February 16th.Thank you very much for doing this for me.

I am doing a project on tooth enamel and acids in the food we eat. I don't know how to explain the words LACTIC, ACID, ACETIC, PHOSPHORIC, and CITRIC to a bunch of 3rd graders. Any suggestions? I know that acid eats calcium. I know that tooth enamel and eggshells are mostly calcium. My hypothesis is lactic acid eats tooth enamel faster than acetic, phosphoric, and citric acid because lactic acid is what is made by the s.mutans in your mouth. Is it true that s mutans mix with saliva and glucose (i think that its your blood sugar) to make plaque and then the plaque uses even more sugar from your food to turn it into lactic acid? Is that the only acid that plaque turns sugar into? And what is the deal with weak and strong acids? is it the weaker the acid the more calcium it eats and opposite for the strong acid? I looked on the internet and found that I couldn't use my baby teeth for the experiement but i could use eggs. The eggshell is the tooth enamel and I put the eggs in 8oz of yogurt (Lactic Acid), 8oz of pickle juice (Acetic Acid), 8oz coca-cola (Phosphoric Acid), and 8oz freshly squeezed orange juice (Citric Acid). I also have one in water to show what no acid will do to your enamel. I'm keeping them at room temperature because i cant get the house as hot as our mouth. They really smell. What is the temperature of our mouth? I can see which one started damaging the egg first (the pickle juice) but how can i measure/compare the changes? I used the measuring tape to measure the size before the test began but eggshell is not that thick so I think I might need another way of measuring the damage. I guess I am comparing damage at different times by taking pictures at the first sign of any changes (4 hours later) and everyday after that. Can you please help? I don't know if I am doing this right.

Answer
Hi Victoria,
I only got your message today because I only have the internet at work.

You've got lots of questions!

Lets start with acids.
Have you discussed what atoms and molecules are in class?
I'll start with with this because this will help with the rest.  


Everything on earth is made up of smaller things, much smaller things than you and I can see with our eyes.
These things are called atoms and everything in the universe is made up of different types of atoms in different combinations.

When you get a few atoms joined together, they're called molecules.
For example, think about a house made out of lego. If you pretend that the lego bricks are atoms, then the house is a molecule. It's made out of different types of lego bricks joined together.
The periodic table is a list of all the different types of atoms there are.

Even gases and liquids are made out of different types of atoms and moelcules. Water is made out of many, many molecules of atoms called hydrogen and oxygen joined together.
Certain types of molecules can react with each other. In the process, some molecules join together, others swap bits  etc.....



Acids dissolve in and react with water. The water changes from two hydrogens and one oxygen to three hydrogens and one oxygen. This new chemical can do all sorts of things. It's especially good at breaking things down. We have acid in our stomachs to break down our food for our bodies to use.


Each of the different types of acids you mentioned are made up of different types of molecules. Some of them are very good at reacting with water, others aren't so good. The ones that react well are strong acids.

lactic, citric and acetic acids are what we call organic molecules because they have lots of carbon ( a specific element/atom). Most organic molecules come from living things.

lactic acid is found in milk. Citric acid is found in lots of fruits. It's also called vitamin c.

phosphoric acid has phosphor in it.

I'll answer more of the question later. I have to get back to work!

Thanks,
Amy