Science Fair Project:

What is in Tap Water?

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Tap water usually contains dissolved gases notably air which is composed mainly of nitrogen and oxygen, along with some carbon dioxide, so when the tap water is allowed to stand some of the dissolved air comes out of the water because liquids in general release dissolved gas as they warm up. This science fair project will illustrate that gases are dissolved in most natural and municipal water.

What are the goals?

Water samples as diverse as tap water to rainwater will be placed in drinking glasses and allowed to sit in a warm place, after a time, bubbles will be seen collecting on the sides of the glass indicating the release of dissolved gases. Based on the results of this investigation a data table will be prepared and the results potted on a graph. A practical benefit gained from conducting this investigation is that the young investigator will be to answer the question "why is the water from the tap bubbly."

Research Questions:

  • Which water sample produced the most bubbles?
  • Which water sample did not produce bubbles?
  • Which water sample produced bubbles the longest and what does this mean?
  • Why is the water from the tap bubbly?
  • Which water sample is the control for this science fair investigation?

Cloudy water from the tap, also known as "white water" as seen in the photograph below, is caused by air bubbles in the water. As the water cools the dissolved air is released to the atmosphere and the bubbling eventually stops. Cold or cool water holds more air than warm water.

In the case of tap water it usually travels from an underground aquifer or reservoir which is cooler than its surroundings for the most part and warms up during its travel to the tap. The air that is present is no longer soluble, and comes out of solution. In addition, once water from a reservoir enters the transmission and distribution pipes, the water is pressurized. Water under pressure holds more air than water that is not pressurized. Once the water comes out of the tap it is no longer under pressure and the air comes out of solution as bubbles (similar to a carbonated soft drink).

Water from almost any source (streams, ponds, lakes, rivers, etc) that is exposed to atmospheric gases (air, carbon dioxide, etc) will act as a solvent and dissolve these gases. The lower the temperature to more gas it can absorb. As the temperature of the water increases, it cannot hold so much gas in solution and some of it separates.

Distilled water if kept in a container free from contact with air after it is goes through the distillation process, is pure water and will not produce bubbles as it cools, distilled water has a flat taste, because air and other dissolved substances which give water its taste have been removed.

Rain is water which has been evaporated from the surfaces of natural bodies of water, oceans, lakes, and from the land, is practically free from particulate material, but contains dissolved gases. The first fall of any shower is mixed with impurities which have been washed from the air. Among these may be carbon dioxide, ammonia, and carbon in the form of soot and creosote.

Most commercial bottled water comes from the same sources as tap water, and like tap water will contain dissolved gasses which will be released upon standing in a warm area. Whether the water is coming out of the tap or from the bottle the amount of dissolved gas depends largely on geographical location and the municipal treatment facility.

Any required diagrams/pictures (Pictures speak a thousand words!)

Digital photos can be taken during the investigating process also the following sites offer down loadable images that can be used on the display board:


What materials are required?

Package of 8 oz plastic drinking cups, distilled water, bottle water, jars, Latex or rubber gloves, and a sample of water taken from a local stream, pond, lake, or river.

Where can the materials be found?

All of the items for this project are available locally at most major retail (Wal-Mart, Target, Dollar general, etc) discount department stores also, a Tri-fold cardboard display board can be purchased from an art & crafts supply store.

Experimental Procedure

  1. On a rainy day collect a jar full of rainwater. Place the jar in a cool place until the day of the investigation.
  2. Using a jar fill it with water collected from a nearby stream, pond, river, or lake.
  3. Set up five clear plastic cups or drinking glasses.
  4. Fill the first cup half full of the water gathered from the field.
  5. Fill the 2nd cup half full of distilled water.
  6. Fill the 3rd cup half full of cold tap water.
  7. Repeat the same procedure using bottle water, and the rainwater.
  8. Place the glasses in a warm place preferable in sunlight. After a time, bubbles will be seen collecting on the sides of the glass this is gases which were dissolved in the water.
  9. Record how long the bubbling last for each sample in a table similar to the one shown below.
Water Source Total Gas (bubbling) Release Time
Stream/pond water
Distilled water
Tap water
Bottle water
  1. On a sheet of graph paper visually display the data in the table by plotting a bar graph of Gas Release Time verse water sample.
  2. The amount of time it takes for the bubbling to stop is displayed along the vertical axis and the water source samples are displayed along the horizontal axis.

Terms/Concepts: Tap water; white water; gas solubility; solvent; distilled water; experimental control


References to related books

Title: Water

Author: Alice Flanagan

Publisher: Coughlan Publishing ISBN-13: 9780756509774 and ISBN: 0756509777

This book about water is written for elementary school age children. The author describes a myriad of water topics including; its cycle, uses, altering states and types, where it is found and how modern technology channels clean water. The book contains interesting water facts, a glossary, and an index along with a resource page. The young investigator will find this book useful to consult for background material for this science fair project.

Title: Water Science Fair Projects, Revised and Expanded Using the Scientific Method

Authors: Madeline P. Goodstein and Tom LaBaff & Stephanie LaBaff (Illustrators)

Publisher: Enslow Publishers, Inc. ISBN-13: 9780766034112 and ISBN: 0766034119

This book offers twenty-four experiments that can be used in conjunction with a science fair project. Starting with a brief introduction about the importance of water, the author leads the reader through a detailed description of the scientific method, how to design an experiment, record data, and tips on how to be produce a successful project. The various chapters in the book cover such topics as the structure of water and provide experiments on molecular structure and solubility. Other chapters address the three states of matter and examines why ice cubes float, how changing from solid to liquid requires heat energy, and the process of distillation. The book contains a glossary and research pages.

Links to related sites on the web

Title: Water


Title: Solubility of Gases


Title:How Water Forms


Title: Why does my tap water look cloudy this winter?

URL: Title: The water we drink URL:

Title: The water we drink


NOTE: The Internet is dynamic; websites cited are subject to change without warning or notice!

Author: Michael Calhoun
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