Category Chemistry

What does mercury in retrograde mean ?

Mercury is the closest planet to the San whipping around our star every 88 days compared to Earth 365.25 days. Mercury will also be the first planet destroyed when the Sun expands on its way to becoming a real giant in about 5 billion years.

So it seems a bit rough that we blame Mercury for all our problems three to four times a year when its in retrograde. But what does it mean when we say Mercury is in retrograde?

A matter of orbits

Retrograde motion means a planet is moving in the opposite direction to normal around the Sun. However, the planets never actually change direction. What we are talking about is apparent retrograde motion, when to us on Earth it looks like a planet is moving across the sky in the opposite direction to its usual movement Because Mercing is closest to the Sun and has the fastest orbit, it appears to move backwards in the sky more often than any other planet. But Mercury isn’t the only planet to do this. Venus also orbits. Inside our oririt of the Sun, ripping around once every 224-7 days. This means Venues is in retrograde twice every three years.

There is also another retrograde. It works the other way around, too. The planets outside our orbit (Mars, jupiter, Saturn Uranus, and Neptune) also go into retrograde. Mars is in retrograde once every two years. The other planets are so far from the Sun and travelling so slowly compared to Earth that its almost like they’re standing still. So we see them in retrograde approximately once a year as we whip around the Sun so much faster than they do

A well-known illusion

Retrograde motion bumboozled act astronomers since humans started looking up in space, and we only officially figures it out when Copernicus proposed in 1543 that the planets are orbiting the Sun (though he wasn’t the first astronomer to propose this heliocentric model).

Before Copernicus, many astronomers thought Earth was the centre of the universe and the planets were spinning around us. Astronomers like Apollonius around 300 BCE saw the planets going backwards, and explained this by adding more circles called epicycles. So, humans found out retrograde motion was an optical illusion 500 years ago. However, the pseudoscientific practice of astrology continues to ascribe a deeper meaning to this illusion.

There’s a retrograde most of the time

 If we consider the seven planets other than Earth, at least one planet is in retrograde for 244 days of 2023 – that’s around two-thirds of the year.

If we include the dwarf planets Pluto and Ceres (and exclude the other seven dwarf planets in the Solar System), at least one planet or dwarf planet is in retrograde for 354 days of 2023, leaving only 11 days without any retrograde motion.

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Have you ever seen water crossing a bridge on its own? Let’s find out by an experiment.

What you need:

Thick tissue paper towels, three glasses, food colours or poster colours

What to do: Arrange the three glasses in a row.

Fill the glasses on both ends with water, leaving the middle one empty.

Add lots of blue colour to the glass on the left, and to the glass on the right, add yellow.

Fold one of the tissues in half lengthwise and place one end in the first glass and the other end in the second. Make sure the tissue touches the bottoms of both glasses without having its middle stuck up too high in the air. If that happens, you can trim the length of the tissues.

The next tissue is placed in a similar manner between the second and the third glasses.

Leave the arrangement, but make sure to keep checking on it intermittently.

What happens:

In a few minutes, we start seeing the coloured water from both the glasses on the edge, climb up the tissue papers. In an hour (maybe more, depending on the thickness of the tissues), the water crosses the paper bridge and starts dripping into the empty glass. In another hour or so, the water level in the middle glass rises as more water from the other two glasses crosses into it. The water in the middle glass is greenish-a mix of yellow and blue colours.

Why?

Water travels up the tissues through a process called 'capillary action’. Capillary action is the movement of a liquid against gravity, through narrow spaces. This is the same principle that allows water to be absorbed by a tree's roots and transported to its leaves.

In this case, the narrow spaces or capillaries are present in the tissues that absorb water, pull it upward and allow it to flow into the middle glass.

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WHEN WAS HELIUM FIRST LIQUEFIED?

On July 10, 1908, helium was liquefied for the first time ever. It was achieved by Dutch physicist Heike Kamerlingh Onnes, who won the Nobel Prize in Physics in 1913 for his low temperature work that led to the production of liquid helium.

Helium is a chemical element that has the lowest boiling and melting points among all the elements. The first in the noble gas group in the periodic table, helium is a colourless, odourless, non-toxic, inert gas in nature. Liquid helium was produced for the first time only in 1908, thanks to the work done by Dutch physicist Heike Kamerlingh Onnes,

Born in Groningen, The Netherlands in 1853, Kamerlingh Onnes father was the owner of a  brickworks and his mother was the daughter of an architect. He received additional teaching in Greek and Latin after spending his time in a secondary school without classical languages in his native town.

Displays his talents early

From 1871-73, Kamerlingh Onnes went to Heidelberg University as a student of German physicists Robert Bunsen and Gustav Kirchhoff. At the age of 18, his talents in the scientific field were apparent as he was awarded a Gold Medal for a competition sponsored by the Natural Sciences Faculty at the University of Utrecht and followed it up with a Silver Medal in a similar event at the University of Groningen the next year.

He was awarded his doctorate by the University of Groningen in 1879 with a remarkable thesis ‘Nieuwe bewijzen voor de aswenteling der aarde’ (New proofs of the rotation of the Earth). After teaching at the Polytechnic School in Delft until 1882, he was appointed to the Physics Chair at the University of Leiden, where he served as a professor until 1923.

Coldest spot on Earth

Inspired by the theories and works of his compatriots Johannes van der Waals and Hendrik Lorentz Kamerlingh Onnes reorganised the Physical Laboratory at Leiden and built up the Cryogenic Laboratory that now bears his name in order to suit his own programme. This meant that Leiden soon established itself as the low-temperature research centre of the world, with some going to the extent of saying that the coldest spot on Earth was situated at Leiden

He spent over a decade perfecting cryogenic experimental techniques, while also studying metals and fluids at low temperatures, Having succeeded in building an improved hydrogen liquefaction machine by 1906, his efforts adminated in the production of liquid helium on July 10, 1908.

On that wet and windy day, Kamerlingh Onnes woke before dawn and headed to his laboratory in the centre of the town, where technicians were already hard at work. Having already increased the stock of liquid air to 75 litres the previous day, they went about the first task of liquefying hydrogen. By 1.30pm, they had produced the 20 litres of liquid hydrogen necessary to launch the attack on helium and stored it in Dewar flasks.

Based on theory, Kamerlingh Onnes knew how much hydrogen they needed and the amount of time the helium experiment would take. It was time to start cooling the helium at 2.30pm, and in just another half an hour, the temperature had already fallen to 93 Kelvin (-180 degree Celsius).

Iterative technique

Kamerlingh Onnes employed the same iterative technique that had allowed their laboratory to produce liquid hydrogen at the increased rate of 4 litres per hour in 1906. This meant that the helium gas that was pre-cooled by liquid hydrogen and liquid air was allowed to expand through a porous plug, thereby cooling to even lower temperatures. This is then recirculated back to the other side of the plug where the expanded helium is further cooled by expanding through the plug again.

By 6.30pm, the temperatures were lower than that of liquid hydrogen and eventually reached 6 Kelvin (-267 degree Celsius). Down to the last flask of liquid hydrogen, Kamerlingh Onnes attached it to the apparatus and the team was wondering if they were destined for failure as the helium had already circulated 20 times with nothing to show for it.

Small teacup of helium

The temperature stabilised at 4 Kelvin (-269 degree Celsius) by 7.30pm when a colleague who came to see how the experiment was going remarked that the thermometer appeared to be standing in a bath of liquid. On closer inspection, Kamerlingh Onnes was able to make out the liquid surface of liquid helium! The experiment had produced just a small teacup of liquid helium, about 60ml to be precise.

Kamerlingh Onnes also discovered and coined the term superconductivity in 1911, demonstrating that the resistance of certain electrical conductors totally disappeared suddenly at a temperature near absolute zero (-273 degree Celsius). The low-temperature studies that resulted in the liquefaction of helium in 1908 helped him win the Nobel Prize in Physics in 1913, 13 years before his death at Leiden in 1926.

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WHAT IS LANDFILL? HOW DO LANDFILLS WORK?

A landfill is a dumping ground for waste materials. It is the systematic disposal of garbage or trash by burying it in the ground. Most modern landfills are designed in a way that they reduce contamination of the nearby groundwater and soil. Nowadays, they are also completely sealed to prevent the methane that is generated by the decomposing waste from diffusing in the environment.

How Do Landfills Work?

Modern landfills are built using a layering system designed to safely isolate waste and monitor any byproducts, leaks and anything else that can harm the environment. Isolating the trash from air and water is vital for preventing contamination.

We can learn more about how landfills work by examining each layer.

Cells (Old and new)

Each day, trash is compacted a cell in order to make the most of the space available in the landfill. The day’s work cell is also known as the daily workface. Here, trash is organized in layers or lifts then compacted accordingly.

Heavy machinery like bulldozers and compaction equipment are used to compress the trash and place it in the landfill. A six inch layer of dirt covers the cell after it’s made and is then compacted once more. This layer helps contain odors and prevent unwanted pests. Some landfills are considering alternatives like tarps or cement emulsions to save space.

The Liner System

The bottom layer of the landfill consists of a liner that keeps trash and byproducts separate from the environment and groundwater. Some facilities use more than one type, but at any landfill you’ll find at least one of the below liners.

Compact clay liners: These liners are normally made of dense, compacted clay solid enough to prevent waste, liquid or gas leaks from seeping into the environment.

Plastic liners: These liners are made of dense plastic and other synthetic materials, normally 30 to 100 mils thick. Plastic liners are typically used in municipal solid waste (MSW) landfills.

The Drainage System

On top of the liner, you’ll find a storm water drainage system that filters out both the liquids produced by trash and the water collected from rain and snow. This layer is important because it separates produced liquids from solid waste. Another drainage system is used to specifically filter out the liquid produced by trash, called leachate, from any rainwater and the rest of the landfill.

Gas Collection System

The gas collection system uses extraction wells and pipes throughout the landfill to carry landfill gas that’s generated when waste decomposes to treatment areas where it is then vented, burned or converted into energy.

Cap

A landfill is permanently capped with a plastic liner when it is full. After it’s capped, the landfill is covered with two feet of soil. Then, vegetation (normally grass and plants without penetrating roots) is planted on top to prevent soil erosion due to rainfall and wind. The landfill is monitored for 30 years to ensure there is no detrimental impact to the environment.

As you can see, today’s landfills are a far cry from the disease-ridden dumps from years before. The industry is also exploring other ways to make landfills cleaner, safer and more environmentally friendly in addition to the processes we’ve already mentioned. See below to learn a few ways landfills are becoming more sustainable.

Credit : Big Rentz

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WHAT IS CHLOROFLUOROCARBONS?

Any of several organic compounds composed of carbon, fluorine, and chlorine, chlorofluorocarbons (CFCS) are non-toxic non-flammable chemicals. If it contains hydrogen in place of one of the chlorines, they are called hydrochlorofluorocarbons (HCFCS) Originally developed as refrigerants in the 1930s. CFCs gained commercial and industrial value as they found use in the manufacture of aerosol sprays, solvents and foam-blowing agents. CFCS, however, were eventually discovered to pose an environmental threat at a serious: level as they contribute to the depletion of the ozone layer and hence are being phased out throughout the world.

What are the applications of CFC?

Chlorofluorocarbons are used in a variety of applications because of their low toxicity, reactivity and flammability. Every permutation of fluorine, chlorine and hydrogen-based on methane and ethane has been examined and most have been commercialized.

Furthermore, many examples are known for higher numbers of carbon as well as related compounds containing bromine. Uses include refrigerants, blowing agents, propellants in medicinal applications and degreasing solvents.

How do CFCs impact the environment?

However, the atmospheric impacts of CFCs are not limited to their role as ozone-depleting chemicals. Infrared absorption bands prevent heat at that wavelength from escaping the earth’s atmosphere. CFCs have their strongest absorption bands from C-F and C-Cl bonds in the spectral region of 7.8–15.3 µm—referred to as “atmospheric window” due to the relative transparency of the atmosphere within this region.

The strength of CFC absorption bands and the unique susceptibility of the atmosphere at wavelengths where CFCs (indeed all covalent fluorine compounds) absorb creates a “super” greenhouse gas (GHG) effect from CFCs and other unreactive fluorine-containing gases such as perfluorocarbons, HFCs, HCFCs, bromofluorocarbons.

Use of certain chloroalkanes as solvents for large-scale application, such as dry cleaning, have been phased out, for example, by the IPPC directive on greenhouse gases in 1994 and by the volatile organic compounds (VOC) directive of the European Union in 1997. Permitted chlorofluoro alkane uses are medicinal only.

According to scientific communities, the hole in the ozone layer has begun to recover as a result of CFC bans. India is one of the few countries that are pioneers in the use of non-Ozone Depleting technologies and have a low Global Warming Potential (GWP).

Credit : BYJUS.com 

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What do we know about the platinum group of metals?

A group of six metals – ruthenium, rhodium, palladium, osmium, iridium, and platinum-are known as the platinum group of metals or PGM. The group is called by this name because platinum is found more than the others though all of them are very rare.

The platinum groups of metals have physical, chemical and anatomical similarities. They are dense, stable and are often recycled to have longer lives. The group has a variety of highly specialized uses.

Platinum is a silvery white metal that is more expensive than gold. It is used to make jewellery. Platinum and palladium are often used as catalysts. Iridium and rhodium are harder and have a lot of alloying applications. There are very few minerals containing the platinum group of metals, and they are found mainly in South Africa and Russia.

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