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.

Solutions and Dissolving

Solutions and Dissolving

What is a solution? 

A solution is a specific type of mixture where one substance is dissolved into another. A solution is the same, or uniform, throughout which makes it a homogeneous mixture . Go here to learn more about mixtures. 

A solution has certain characteristics:

• It is uniform, or homogeneous, throughout the mixture
• It is stable and doesn't change over time or settle
• The solute particles are so small they cannot be separated by filtering
• The solute and solvent molecules cannot be distinguished by the naked eye
• It does not scatter a beam of light

Example of a Solution 

One example of a solution is salt water which is a mixture of water and salt. You cannot see the salt and the salt and water will stay a solution if left alone. 

Parts of a Solution

• Solute - The solute is the substance that is being dissolved by another substance. In the example above, the salt is the solute.
• Solvent - The solvent is the substance that dissolves the other substance. In the example above, the water is the solvent.

 
A solution is a type of homogeneous mixture

Dissolving 

A solution is made when one substance called the solute "dissolves" into another substance called the solvent. Dissolving is when the solute breaks up from a larger crystal of molecules into much smaller groups or individual molecules. This break up is caused by coming into contact with the solvent. 

In the case of salt water, the water molecules break off salt molecules from the larger crystal lattice. They do this by pulling away the ions and then surrounding the salt molecules. Each salt molecule still exists. It is just now surrounded by water molecules instead of fixed to a crystal of salt. 

Solubility 

Solubility is a measure of how much solute can be dissolved into a liter of solvent. Think of the example of water and salt. If you keep pouring salt into water, at some point the water isn't going to be able to dissolve the salt. 

Saturated 

When a solution reaches the point where it cannot dissolve any more solute it is considered "saturated." If a saturated solution loses some solvent, then solid crystals of the solute will start to form. This is what happens when water evaporates and salt crystals begin to form. 

Concentration 

The concentration of a solution is the proportion of the solute to solvent. If there is a lot of solute in a solution, then it is "concentrated". If there is a low amount of solute, then the solution is said to be "diluted." 

Miscible and immiscible 

When two liquids can be mixed to form a solution they are called "miscible." If two liquids cannot be mixed to form a solution they are called "immiscible." An example of miscible liquids is alcohol and water. An example of immiscible liquids is oil and water. Have you ever heard the saying "oil and water don't mix"? This is because they are immiscible. 

Interesting Facts about Solutions

• There is a solvent called aqua regia which can dissolve the noble metals including gold and platinum.
• You can't see a beam of light when shining it through a true solution. This means fog is not a solution. It is a colloid.
• Solutions can be liquid, solid, or gas. An example of a solid solution is steel.
• Solids are generally more soluble at higher temperatures.
• Carbonated beverages are made by dissolving carbon dioxide gas into liquid at high pressure.

Separating Mixtures

Separating Mixtures

Many of the substances we use everyday were actually once part of a mixture. Someone somewhere separated that substance from the mixture so we could use it. It turns out that many compounds and elements aren't found in nature in their pure form, but are found as parts of mixtures. Separating substances from mixtures is an important part of chemistry and modern industry. 

Some important chemistry terms are used in this section including mixtures, suspensions, andsolutions. You can click on the links to learn more about each of them. 

Why do we want to separate mixtures? 

All the way back to Ancient History, industrious humans have separated mixtures in order to obtain the specific substances that they need. One example of this is extracting metal from ore in order to make tools and weapons. We'll discuss some other examples of separation below. 

Separation Processes 

The way in which different substances in a mixture are separated is called a process. There are a number of different processes used for separation. Many of them are very complex and involve dangerous chemicals or high temperatures. A lot of important industries in the world today are based on separation processes. 

Filtration 

One common method of separation is filtration. Filters are used everywhere. We use them in our houses to filter dust and mites out of the air we breathe. We use them to filter impurities from our water. We even have filters in our bodies such as our kidneys which act as filters to get bad stuff out of our blood. 

The filtration process is generally used to separate a suspension mixture where small solid particles are suspended in liquid or air. In the case of filtering water, the water is forced through a paper that is made up of a very fine mesh of fibers. The water that has been run through the filter is called the filtrate. The particles that are removed from the water by the filter are called the residue. 

Distillation 

Another common separation process is called distillation. Distillation uses boiling to separate mixtures of liquid solutions. It takes into account that different substances in the mixture will have different boiling points. 

For example, if you heat salt water the water in the solution will boil before the salt. The water will then evaporate leaving the salt behind. If the steam from the water is collected it will turn back into liquid as it cools. This cooled water will be pure water without any salt. 

Centrifuge  In some cases, there are suspension mixtures where the solid particles are too fine to be separated with a filter. In these cases, sometimes a centrifuge is used. Centrifuges are mechanical devices that spin at very high speeds. These high speeds allow the solid particles in suspensions to settle very quickly. For example, rather than wait for sand to slowly settle to the bottom of water, a centrifuge can cause the sand to settle in a matter of seconds.  Some examples of how centrifuges are used include separating blood into plasma and red cells, separating cream from milk, and separating uranium isotopes for nuclear power plants.

The heavier particles move to the outside of the cylinder as the centrifuge spins allowing the mixture to be separated.

Other Processes 

There are many other separation processes such as sublimation, adsorption, crystallization, and chromatography. Sometimes it takes many stages of processes to get to the final result. One example of this is the processing of crude oil. Crude oil uses many levels of fractional distillation to produce a number of different products including gasoline, jet fuel, propane gas, and heating oil. 

Interesting Facts about Separating Mixtures

• To separate liquid solutions where the substances have similar boiling points, a more complex version of distillation is used called fractional distillation.
• Painting uses the separation process of evaporation. The wet paint is a mixture of color pigment and a solvent. When the solvent dries and evaporates, only the color pigment is left.
• The separation process of winnowing was used in ancient cultures to separate the grain from the chaff. They would throw the mixture into the air and the wind would blow away the lighter chaff, leaving the heavier grain.
• High speed centrifuges can spin up to 30,000 times a minute.
• Many separation processes are occurring constantly in nature.

This is London

An introduction to Britain