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

HOW CAN WE MOTIVATE OURSELVES MORE EFFECTIVELY THROUGH REINFORCEMENT?

By
•We'd all like to be more effective in reaching our goals, and according to behaviorists, the way to improve our effectiveness is by rewarding ourselves for the little steps that take us closer and closer to those desirable outcomes.  •First, find something you really like to do or something you'd like to have that can, realistically, serve as a reward.  •Then, take the goal that you are hoping to achieve that, realistically, you could achieve but just haven't succeeded at yet.  •Next, work backward from that goal to your present state.  •Arrange to give yourself those desired rewards as you inch closer from where you are now to the desired end point.  •As you start to make progress, only give yourself a reward when you've moved forward from where you are now.  •For example, if you'd like to cut back on your television watching and instead read more often, reward yourself by allowing yourself to watch television only when you've read for 20 minutes,
Post a Comment
Read more

15 Did You Know Fact that will surprise you

By
1) Did you know that this colourful little chap is the Costa Rican Variable Harlequin toad aka the Clown frog. 2) Did you know that the Karni Mata Hindu Temple in Rajasthan, India, is also known as the Temple of Rats. The temple is famous for the approximately 25,000 revered black rats that live there. Visitors play with and feed the rats and even sometimes drink from the same milk and eat the same food. 3) Did you know that vanilla flavoring is sometimes made with the urine of beavers. 4) Did you know that Botox is made from botulinium toxin which is considered the most deadly substance in the World as half a pound would be enough to wipe out the entire World population. Almost all the Botox in use throughout the World is made in one single factory in Ireland. 5) Did you know that tuna swim at a continuous steady rate of about 14km per hour for their whole life until they die. Whilst alive they never stop moving as if they stop they are unab
Post a Comment
Read more

AMAZING FACTS ABOUT KANGAROOS

By
Kangaroos only sweat while they are hopping. When they stop exercising, they pant, just like dogs do. A kangaroo mother may have a newborn joey and a much older baby (called a yearling) nursing at the same time. Each one will get milk that is formulated to suit him best nutritionally. Strangely, kangaroos burn less energy the faster they hop… up to 20 miles per hour. A group of kangaroos is called a mob. A male kangaroo is called a buck, a boomer, or an old man. A female kangaroo is called a doe or a flyer. For a long time, people thought the word kangaroo meant "I don't know" in an aboriginal Australian language. Probably, the word comes from gangurru, a native name for one kind of kangaroo. 
Post a Comment
Read more