Skip to main content

WHY IS LEAD USED IN PENCILS EVEN THOUGH LEAD IS POISONOUS?

By

Why is lead used in pencils even though lead is poisonous?

•The core of a pencil does not contain lead and never has. Pencils contain a form of solid carbon known as graphite. 

•According to a study, the graphite pencil was first developed and popularized in the 1600's. 

•The first users of graphite simply dug this mineral out of the hills and discovered it could be sawed into sticks and used as an excellent writing tool. 

•During the 1600's, no one knew the chemical nature of this material, as chemistry itself was still in its infancy.

•Since this writing material behaved similar to metallic lead, but had a darker color, people began calling it "black lead". 

•Eventually, the name of the core of the pencil got shortened to "lead". In 1779, German chemist K. W. Scheele finally determined pencil lead to be composed of pure carbon. 

•A decade later, A. G. Werner decided that this carbon material needed a new name and proposed the name "graphite" based on the Greek word "graphein" which means "to write". 

•Black-core pencils currently contain and have always contained graphite, not lead.


•Carbon is the sixth element on the periodic table and is famous for forming the backbone of molecules found in fuels and in all living organisms. 

•Aside from biological molecules, carbon can also be found in nature in pure mineral form. 

•Depending on the shapes in which the carbon atoms are bonded, pure carbon can take on many forms.

•In diamond, each carbon atom is bonded tetrahedrally to its four nearest carbon atoms. This tightly packed arrangement of carbon atoms makes diamond the hardest naturally occurring material on earth.

•In contrast, graphite contains a stack of carbon sheets. Each carbon sheet is one atom thick and consists of a hexagonal lattice of carbon atoms bonded together.

•Each carbon atom in the sheet is bonded to the three nearest carbon atoms. The carbon atoms within a sheet are very strongly bound together, but the sheets themselves are very weakly bound. 

•As a result, it is very easy for one carbon sheet in graphite to slip past the other sheets. This slippery-sheet structure is what makes graphite so oily to the touch and makes it such a good material to write with. 

•The carbon sheet fragments readily rub off the pencil core and onto the paper. This property also makes graphite powder an ideal dry lubricant.

•When a small single graphite sheet is bent into a circle and connected back to itself, it can form a carbon nanotube, which is a promising object that should find application in future technology.

Labels:

Comments

Post a Comment

Popular posts from this blog

Why do the Indian telecom operators offer their services with 28 days validity, not 30 days?😡😡

By
Here telecom operator are very clever, b ecause telecom operators want to earn money of 13 months instead of 12 months. Let do the calculation and find out why telecom operators are offering 28 days validity. Each month they get 2 days more, therefore in a year they get additional 24 days. There are 7 month which has 31 days so they get additional 7 days.Now in case of February  ,it has only 28 days not 30. So the total number of days they get are=24+7-2=29 days. So if you recharge 12 times then more 29 days are left in a year.🤔🤔 Means for another 29 days you have to recharge from that telecom operator.😫😫 So you have to recharge 13 times in a year instead of 12 times in a year. So telecom operators provide 28 days validity only. First one telecom operator started and then another telecom operators also understood this concept and they also applied 28 days validity both in data packs and voice packs.😱😱😱
Post a Comment
Read more

20 Interesting science fact (PART 1)

By
1/ The speed of light is generally rounded down to 186,000 miles per second. In exact terms it is 299,792,458 m/s (metres per second - that is equal to 186,287.49 miles per second). 2/ It takes 8 minutes 17 seconds for light to travel from the Sun's surface to the Earth. 3/ October 12th, 1999 was declared \\"The Day of Six Billion\\" based on United Nations projections. 4/ 10 percent of all human beings ever born are alive at this very moment. 5/ The Earth spins at 1,000 mph but it travels through space at an incredible 67,000 mph. 6/ Every year over one million earthquakes shake the Earth. 7/ When Krakatoa erupted in 1883, its force was so great it could be heard 4,800 kilometres away in Australia. 8/ The largest ever hailstone weighed over 1kg and fell in Bangladesh in 1986. 9/ Every second around 100 lightning bolts strike the Earth. 10/ Every year lightning kills 1000 people. 11/ In October 1999 an Iceberg the size of London broke free...
Post a Comment
Read more

A brief history of the Morse code

By
££) In  the early nineteenth century, all of the essential components necessary to construct an electrical communication system had been discovered. The most important of these were the battery by Volta, the relationship between electric current and magnetism by Oersted, and the electromagnet by Henry. It now remained for someone to find a practical method to combine these technologies into a working communication system. ££)Some  commercial electrical communications systems existed in Europe as early as the 1830s. A classic example of this is the English ‘Needle Telegraph’. The needle telegraph required two or more lines to form a complete circuit. It was relatively slow and the design of the transmitting and receiving instruments was complex. Something simple and efficient was needed. ££)The  Morse system of telegraphy was invented by Samuel Finley Breese Morse (an American painter and founder of the National Academy of Design in New York) in the 1840s ...
Post a Comment
Read more