Graphite is used in pencils because of its ability to leave gray marks on paper. It was originally thought to be a form of lead.Know More
In spite of the name, lead pencils do not actually contain lead. During the Roman Empire, lead rods were used for writing on papyrus. In the 16th century, a large deposit of graphite was discovered in England; shortly after this discovery, graphite became a common material used for writing. It was originally thought to be a darker form of lead and was therefore given the name "Blacklead" or "plumbagoi."
In the late 1700s, a Swedish chemist determined that graphite was a form of carbon rather than lead. The name of the substance was soon changed to graphite, after the Greek word for "to write."
Ink was commonly used for writing — applied using a device called a "peniculus" — from which the word "pencil" is derived. Early forms of pencils involved a graphite rod wrapped in string and inserted into hollow sticks. Eventually a mixture of graphite and clay was developed that eliminated the need for string and produced a harder substance that could easily be inserted into hollow rods. Altering the ratio of graphite to clay produces variations in the darkness of the markings made by the pencil. Adding other materials such as dye, wax, water or charcoal can produce pencils used for other purposes, including cosmetics and art.Learn more about Atoms & Molecules
The alkali metal sodium is used in making table salt as well as baking soda, borax and the sodium lamps that illuminate highways. Potassium is another alkali metal and is used in making fertilizers, inks, matches, dyes and fireworks.Full Answer >
Nitric acid is commonly used in food processing, as fertilizer and as an oxidizing agent for rocket fuels. It also contains chemical properties necessary for certain explosives.Full Answer >
Helium is used for applications ranging from sending rockets into space to helping deep sea divers breathe. Helium is also at work in the balloons at parties or in the blimp floating overhead at a ball game. It is also used as a coolant in nuclear reactors, the Large Hadron Collider, satellite instruments and MRI scanners.Full Answer >
Elements from the lanthanide series are used for petroleum production, lasers, magnets, projectors, X-ray screens and as a component of steel and magnesium alloys. The lanthanides are soft, highly reactive metals that burn easily and act as strong reducing agents.Full Answer >