Water is the most important substance on Earth. Without it, there would be no plants, no animals, no life. The human brain is approximately 85% water, and if you lost 10% of the water in your body you would not be able to walk. A loss of 20% would be the end of you.

As we are constantly losing water we need to take in more to replace it. Although there is a huge amount of water on Earth, 97% of it is in the oceans and far too salty to drink. Of the fresh water, most is frozen in the polar ice caps. Even so, there is plenty of water around (in most places anyway) in the form of rivers and lakes, both above and below ground. As we use this water, it is replaced by natural processes - part of the water cycle.

Water has many unusual properties, and is a special compound because many substances dissolve in it. This means all the special molecules that make up you and me and all other life can meet together in solution and react.

1) Most of the water in water cycle is in the oceans and seas of the world. The sun's energy, which drives the water cycle, heats the water, which evaporates (becomes a gas).

2) This also happens to water on land, in rivers and lakes, and from the leaves of plants, when it is called transpiration.

3) The sun also heats the surface of the planet, which in turn heats the air near the ground. This causes the air to rise, taking the evaporated water with it. As the air rises, it cools, and can no longer hold as much water. The water condenses back to a liquid, forming droplets, which form clouds.

4) When the drops reach a critical size, they fall from the sky as rain (or more generally, precipitation, which includes rain, snow, hail, and all other water falling out of the sky).

5) The water falls on the oceans, or on the land, where it runs together in rivers and percolates through the rock on it's way back to the sea. As it travels itis used by us and all the other animals and plants. The cycle is never ending, going round and round, driven by the sun's energy.

The water that comes out of your taps at home is very different from the water found in rivers and lakes. Natural water is cloudy (due to colloidal particles) and contains bacteria. The water companies remove both of these during the treatment process.

Solid particles are removed by a process called coagulation. This involves the addition of aluminum or iron ions, which attract the small negatively charged particles so that they comes together to form a precipitate. This is then filtered from the water using filters of fine sand (and sometimes activated carbon). The use of aluminum ions also leads to an increase in the acidity of the water (a drop in pH). To counteract this a base (or alkali), such as sodium hydroxide is added.

Disinfection of the water is achieved by adding chlorine. Chlorine is very soluble in water so is simply dissolved in the supply. Often, ammonia is added to the water after chlorination to form chloramines. These are less effective than free chlorine in killing bacteria, but have the added advantage of persisting longer in the pipes that supply homes and businesses. This is called a residual disinfectant. Another chemical that is sometimes used is sulphur dioxide. This removes excess chlorine, allowing the dosing to be carefully controlled.

The quality of water is very carefully measured by water companies and also several regulating bodies. Water is analyzed for metal ions (such as cadmium, lead and copper), bacteria, chlorine, and also the turbidity (cloudiness) and color.

Evaporation, Condensation and Precipitation
Observe the water cycle in the privacy of your own kitchen

The lenses are mounted usually in two tubes, which can be slid in and out from one another in order to focus. The objective lens will be set in the end of the larger tube, and the eyepiece will be set in the end of the smaller. To determine how far the lenses are to be mounted from one another, hold the smaller lens to your eye. Hold the larger one up in front of it, and try to focus a clear image of a distant object. Measure how far the lenses are at this point. That should be about midrange for the combined length of the tubes.

The lenses can be held in place with epoxy, taking care not to spill any epoxy on the faces of the lens. If the lens is smaller than the opening, a gasket can be improvised from wood, cork, heavy cardboard, or some such. Make certain that the lenses are aligned with one another, that is, they are both set in the same plane vertically and horizontally (center to center) before fixing in place. Look through the eyepiece. If you see no image or only a partial image, then the lenses are not aligned. The finished product will be adequate for exploring the moon's surface. Don't look at the sun with it! It will severely damage your eye.

Two convex lenses will create an upside down image, which is exactly what the telescope described above does. Some telescopes and binoculars use rectifiers, an optical system usually incorporating a prism, to turn the image right way up again. An upside down image really doesn't matter so much when you are exploring the surface of the moon. What you sacrifice in orientation you more than make up for in lightness and power.

If you are building a terrestrial telescope, or "spy glass", you probably don't want an upside down image. Substitute a concave lens for the eyepiece. The telescope won't be as strong, but it will be adequate for most land use. This type of telescope is also known as a Galilean telescope, because it was first built by Galileo and used by him when he discovered the moons of Jupiter.

It is a very simple matter to make a formula for blowing bubbles using liquid household dishwashing soap and water. The water should be soft, or, better yet,

distilled. Hard water or water heavy in mineral content will make fragile bubbles that will not last as long.

As far as the dishwashing soap, most sources agree that the best to use is either Dawn or Joy (U.S.). Other brands will work, but not nearly as well. In summary any soap that makes good bubbles should work.

The ratios to mix soap to water vary widely according to the source. Like any recipe, everyone has his or her own way of cooking the brew. Water quality and local climate (especially humidity) will determine what mixture works best in your area, so experiment to get the best formula to work with. The average range is 10 parts water to one part soap. Ultra Joy and Ultra Dawn are more sudsy, so less is required, maybe 15 or 20 parts water to one part soap. Mix well and allow to sit for a day or so to stabilize.

How long a bubble lasts is dependent on how long it can stay wet. Glycerin will slow down the drying time very well. So will sugar, Karo syrup (corn sugar syrup), and gelatin. Solutions with glycerin keep better over longer periods of time, but sugar and gelatin are less expensive and one or the other is probably already lying around the kitchen. Again, the amount added varies with climate and water, but start experimenting with around .10 parts (1/10 part, NOT 10 parts!) gelatin, or .25 parts Karo syrup, sugar, or glycerin in the above formulae.

The formula is an especially stout mixture for very big bubbles, and uses 2 parts detergent, 4 parts glycerin, and 1 part white Karo syrup. This is serious stuff!

Tools

Suggestions for various soap bubble "tools". The basic wire loop - Take a short piece of thin but stiff wire and form a loop in it about 4 cm (1 1/2 inches) in diameter. Dip into the bubble solution and gently blow.

Drinking straws make fairly good bubble blowers. They will hold more bubble juice if 4 short slits ( 2" or 50mm) are cut at the bubble end. The resulting tabs should splay out.

The big bubble loop - Slide two drinking straws onto a piece of string about 1 meter (1 yard) long. Tie off the ends to form a loop. Hold the straws apart to form a big rectangle. Bring the straws together to close the rectangle and dunk it into a bucket of bubble juice (it is best to make a stiffer solution for this, using more glycerin and/or Karo syrup). Pull it out again and slowly separate the two straws. A film should form around the loop. If it doesn't break, pull the loop through the air to form a giant bubble.

Colors

Soap bubbles are a layer of soap film on the outside, a layer of water molecules in the middle, and a layer of soap film on the inside. Light reflects from the first and second layer of soap film. The light waves interfere with each other, adding to or subtracting from each other's frequencies, which changes the color reflected.

The interference colors are determined by how far the light waves that are reflected from the inside layer must travel to meet the waves reflected from the outside layer. So the different colors of the bubble actually correspond to its thickness at different points.

Shape

Soap bubbles are elastic and will contract to form a sphere, which provides the most volume for the least surface area.

Bubble tank

To build a bubble tank you need a large clear box that is open at the top. An empty aquarium will work well, but a tall narrow tank built from Plexiglas is better. It should be about 1 meter or 1 yard tall and 1 foot or 30cm square at the base.

Place a rag or dishtowel in the bottom of the box, and on top of that place a piece of dry ice. Let it sit for a minute or so. Some of the carbon dioxide in the dry ice will evaporate as carbon dioxide gas. Since it is denser than the surrounding air, it stays in the bottom of the box. If bubbles are now blown into the box, they will sink to the top of the carbon dioxide layer and float there. Don't actually blow into the box; you will probably blow out most of the carbon dioxide. Bubbles are semi-permeable, meaning there are tiny holes in them large enough to let some gas molecules through, but not others. Carbon dioxide can fit through these holes. Gradually, the carbon dioxide gas diffuses into the bubbles, causing them to grow.

If you don't have access to dry ice, you can mix a small amount of vinegar and baking soda in a container at the bottom of the chamber. They will bubble and produce carbon dioxide. Once the bubbling stops, there should be enough carbon dioxide for the bubbles to float.