Why is the sky so blue?

Have you ever tried asking this question why the sky is blue in colour to your teacher? It is interesting to know what renders the blue colour to the vast sky. Definitely there is an answer to such questions. Let us find out the answer right away.

Everyday Chemistry - Why is the sky so blue?
Right from childhood, our teachers have drilled the fact that the sky is blue in colour into our heads. But do you know what renders the blue colour to the sky? Let us find out the answer right away.
What is colour?
Let us first understand how we perceive colours. Colours are just properties of certain objects. Every matter contains molecule of different configurations. When light hits the object, it gets affected by the material and gets scattered everywhere because of the presence of the molecules. The light thus emitted has some colour to it and our eyes perceive them as a particular colour.
How did sky get its colour?
The earth is also an object. It has an atmosphere with gaseous substances like oxygenand nitrogen. When light from the sun hits earth, the molecules of oxygen and nitrogen scatter in all direction. The light from the sun contains several colours like violet, red, orange and yellow. The colour depends on the wavelength of the radiation. The scattering of the molecules also depends on the wavelength, the longer the wavelength the longer the scattering is and vice versa.
Our human eye senses three primary colours, red, green and blue. The blue component is almost ten times stronger than red and violet. Hence even as the earth's component contains red and violet, the human eye views it as blue. When we view the sky away from the sun it appears blue in colour. This is true only on clear sky days. Sometimes when the light emitted by the sun has more of red then we get an orange looking sky. This is true during sunrise or sunset. On days when there are extra particles in the earth's atmosphere like haze, the sky does not seem blue to us.

So the next time you colour sky in your drawings, feel free to colour it orange!

Vinegar and its winning properties

If you have seen copper or bronze statutes or curios you may have noticed that they turn black or green in colour. Did you know that you can use vinegar to clean this?

What is Vinegar?

Vinegar is made by fermenting ethanol which produces acetic acid. The ethanol that is used in the process can be derived from wine, beer, fermented fruit juice or cider. Along with acetic acid, vinegar has amounts of tartaric acid, citric acid, and other acids. There are various kinds of vinegar including malt vinegar, wine vinegar, apple cider vinegar, fruit vinegar, balsamic vinegar, rice vinegar, coconut vinegar, palm vinegar, cane vinegar, and raisin vinegar.

Along with acetic acid, vinegar has amounts of tartaric acid, citric acid, and other acids.

How is vinegar made?

Commercially, vinegar can be made by using either a slow or fast fermentation process. The slow fermentation process takes weeks or months. During this process a non-toxic slime called mother of Vinegar forms. This slime consists of acetic acid bacteria and soluble cellulose. The same Mother of Vinegar is used in the fast fermentation process. It is added to the liquid from which the Vinegar is to be produced. A turbine is used to oxygenate the mixture. This helps in reducing the time needed to ferment the Vinegar to anywhere between 20 hours to three days.

Cleaning Properties of Vinegar

Brass and copper loose its shine because of exposure to moist air. The exposed metal form compounds with high carbon dioxide and sulphur dioxide. When copper is exposed to the environment, various layers of minerals that contain oxides, sulphate, sulphides, carbonates, chlorides, and hydroxides accumulate on the metal. This discolouration is called patina. Vinegar gives those green and faded copper utensils, brass items, and chrome surfaces that long last shine. It’s an age-old remedy that involves mixing vinegar and salt and rubbing the resulting liquid over the copper surface to revive the lustre. The acetic acid present in vinegar dissolves the tarnish on these metals.

Why do some balloons float upwards and others don't?

Every one loves balloons. Round, colourful and they explode with a bang.
Have you wondered why the balloons we blow ourselves don't float, while some float up and away?
Hold your breath...the secret is about to be revealed. 

Floating in general
We are all comfortable with things that float in water. We see that happen every day - the paper ships we send floating in rainwater and the plastic toys that keep us company in the bath tub. In fact, in swimming pools we have seen people float in water. The same reason why things float in water applies to air as well.
Let's say that you take a plastic 1-liter soda bottle, empty out the soft drink, put the cap back on it (so you have a sealed bottle full of air), tie a string around it like you would a balloon, and dive down to the bottom of a swimming pool with it. You can sit at the bottom of the pool with it, holding the string, and it will act just like a helium balloon does in air. If you let go of the string the bottle will quickly rise to the surface of the water.
The reason that this soda bottle "balloon" wants to rise in the water is because water is a fluid and the 1-liter bottle is displacing one liter of that fluid. In other words, because we introduced the bottle in the pool, the bottle pushed away some amount of water to make space for it.
The bottle and the air in it weigh perhaps an ounce at most (1 liter of air weighs about a gram, and the bottle is very light as well). The liter of water it displaces, however, weights about 1,000 grams (2.2 pounds or so). Because the weight of the bottle and its air is less than the weight of the water it displaces, the bottle floats. This is the Law of Buoyancy.
The Helium Balloons
Now that we understand why things float, let's get back to balloons. The reason why some balloons float while others don't is because of the presence of a gas called Helium. Balloons filled with Helium float in air, while the one with just air don't.

Now, Helium balloons work by the same law of buoyancy. In this case, the Helium balloon that you hold by a string is floating in a "pool" of air (when you stand underwater at the bottom of a swimming pool, you are standing in a "pool of water" maybe 10 feet deep -- when you stand in an open field you are standing at the bottom of a "pool of air" that is many miles deep). The Helium balloon displaces an amount of air (just like the empty bottle displaces an amount of water). As long as the helium plus the balloon is lighter than the air it displaces, the balloon will float in the air.