[(USGS logo)] U.S. Geological Survey

 

Water Questions and Answers: Chemical Properties

 

Select a question that interests you:

1. Why does my water smell like rotten eggs?

2. Why does it take so long to rinse the soap off my hands?

3. How does our swimming pool stay so clean?

4. Why is our porcelain sink stained brown?

5. Why are some lakes I see full of algae and thick plants?

-------------------------------------------------------------------------

(1) Q: Why does my water smell like rotten eggs?

 

A: You would know it if you had this problem! In some parts of the country,

drinking water can contain the chemical hydrogen sulfide, which smells just

like rotten eggs. This can occur when water comes into contact with organic

matter or with some minerals, such as pyrite. The situation mostly occurs as

ground water filters through organic material or rocks.

----------------------------------------------------------------------------

(2) Q: Why does it take so long to rinse the soap off my hands?

 

A: The terms "soft water" and "hard water" are important here. Water is said

to be "soft" if it has a low concentration of calcium and magnesium ions in

it, and "hard" water has a higher concentration. The ions react with the

soap you use to produce a scummy residue that is hard to wash off. If you

use "hard" water you also will have a harder time working the soap up into a

lather. "Hard" water is prevalent in some parts of the country, and

sometimes "water softening" chemicals, that reduce the amount of calcium and

magnesium, are added to the water.

----------------------------------------------------------------------------

(3) Q: How does our swimming pool stay so clean?

 

A: It is not an easy task to keep a swimming pool so clear and clean. If you

just set a pan of water out in the middle of summer you'll see that it fills

up with gunk very quickly. People have to resort to both chemical and

physical means to keep the water clean and safe for swimming. The water is

continuously pumped through a filter to trap particles, like all those bugs

that fall in, and to keep algae and dangerous bacteria from growing,

chemicals such as chlorine are added. Chlorine also is added to your

drinking water to keep those bacteria out of your stomach.

----------------------------------------------------------------------------

(4) Q: Why is our porcelain sink stained brown?

 

A: The brown stain is from too much iron in your water. It is closely

related to simple rust you see on metal, which is iron oxide. Probably the

source of the water you use is ground water, and the water has filtered

through rocks containing iron-rich minerals on the way to the well.

----------------------------------------------------------------------------

(5) Q: Why are some lakes I see full of algae and thick plants?

 

A: First of all, plants naturally grow in and around lakes. Maybe you're

asking about a lake that is being chocked off from so much algae. In many

cases, man is to blame. Actually these lakes are being fed too much food!

There are certain chemicals we use that are nutrients to plants. At our

homes we fertilize our yards with nitrogen, potassium, and phosphorus. These

chemicals wash off our lawns and eventually get into the water system, such

as into creeks, rivers, and lakes. Once there, algae and plants have a feast

on this "food". Things used to be worse for our water bodies. Phosphorus

used to be an ingredient in our laundry detergent, but this has generally

been phased out.

----------------------------------------------------------------------------

USGS Water-Use home page

The URL for this page is

http://h2o.er.usgs.gov/public/watuse/wuqa.chemical.html

If you have questions or comments about this document contact

hperlman@usgs.gov

Last modified: 10/11/95

 

Tapwater home

Activity Page

Observe

Resources

The Source

Teacher's Corner

How did you do?

SCORE Science