What are allotropes of carbon

 Allotropes of carbon

Allotropes or allotropism is the property of some chemical elements to exist in two or more different forms , in the same physical states ,known as allotropes of the element.

Diamond :In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure. Diamond is the hardest substance known while graphite is smooth and slippery. 

Graphite: In graphite, each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array. One of these bonds is a double-bond, and thus the valency of carbon is satisfied. Graphite structure is formed by the hexagonal arrays being placed in layers one above the other.  Graphite is also a very good conductor of electricity. 

These two different structures result in diamond and graphite having very different physical properties even though their chemical properties are the same. Diamonds can be synthesised by subjecting pure carbon to very high pressure and temperature. These synthetic diamonds are small but are otherwise indistinguishable from natural diamonds.

Fullerenes: form another class of carbon allotropes. The first one to be identified was C-60 which has carbon atoms arranged in the shape of a football. Since this looked like the geodesic dome designed by the US architect Buckminster Fuller, the molecule was named fullerene.

What is Hypotonic solution, Isotonic solution and Hypertonic solution

What is Hypotonic solution, Isotonic solution and Hypertonic solution

Hypotonic solution: If the medium surrounding the cell has a higher water concentration than the cell, meaning that the outside solution is very dilute, the cell will gain water by osmosis. Such a solution is known as a hypotonic solution.
Water molecules are free to pass across the cell membrane in both directions, but more water will come into the cell than will leave. The net (overall) result is that water enters the cell. The cell is likely to swell up.

Isotonic solution: If the medium has exactly the same water concentration as the cell, there will be no net movement of water across the cell membrane. Such a solution is known as an   isotonic   solution.  Water crosses the cell membrane in both directions, but the amount going in is the same as the amount  going out, so there is no overall movement of water. The cell will stay the same size.

Hypertonic solution: If the medium has a lower concentration of water than the cell, meaning that it is a very concentrated solution, the cell will lose water by osmosis. Such a solution is known as a hypertonic solution.