Knowledge of Science

Blood circulatory system    (Blood vascular system ) Blood circulatory system is regarded as a kind of vascular system and therefore, it is called blood vascular system. A vascular system is that which has tubes full of fluid to be transported from one place to another.  The blood vascular system comprises of heart, the organ which pumps and receives the blood, and blood vessels, which are tubes through which the blood flows.      Blood vessels- The blood vessels are elastic muscular tubes which carry blood. There are three kinds of blood vessels in human body.     They are of three types-(1)Arteries  (2)veins and  (3)capillaries. (1)Arteries- Arteries are the thick walled blood vessels which carry blood away from the heart for distribution to the body. The walls of arteries particularly those near the heart are thick that enables them to dilate but not rupture when the heart contracts and forces blood into them. Thus the blood passing through narrow lume

      Excretion in human beings Excretory system- Excretory system in human beings (also known as urinary system) consists of a pair of kidneys, a pair of ureters ,a urinary bladder and a urethra . The two kidneys are located towards the back of the lower part of the abdominal cavity, one on either side of the backbone. Left kidney is slightly larger and placed a little higher than the right kidney. The blood from aorta enters into kidneys via the renal arteries and returns to the posterior Vena cava via renal veins. Urine formed in the kidneys passes by a pair of ureters to the bladder where it is stored until it is released via the urethra. Structure and function of kidneys- There are two kidneys in humans each kidney is purplish- brown, slightly flattened and shaped somewhat like rajma Bean. It is about 12 centimetre long, about 6 CM thick and wait about 150 grams. Internally a kidney is made of numerous microscopic excretory units called nephrons. Single kidney contai

      Refraction of light The change in direction of light when it passes from one medium to another obliquely is called refraction of light.           In other words the bending of light when it goes from one medium to another obliquely is called refraction of light.           The  Refraction of light  takes place when light rays enter from air into glass , or from glass into air. The refraction of light takes place when light enters from air into water, or from water into air. And the refraction of light also takes place when light enters from water into glass or from glass into water.        The optical instruments like camera, microscope and telescope work on the the refraction of light through glass lenses.     The refraction (or bending ) of light takes place at the boundary between the two media. Causes of refraction- The refraction of light  is due to the change in the speed of light on going from one medium to another. Thus, when light goes from one medium to

Trichloromethane  (chloroform)       CHCl3  Trichloromethane is a trichloro derivative of methane. It is commonly called as chloroform. Methods of preparation-  It is prepared by the chlorination of methane in the presence of sunlight.          Sunlight CH4 -------------------> CH3Cl + HCl             +Cl2              Sunlight CH3Cl ---------------> CH2Cl2+ HCl                +Cl2              Sunlight CH2Cl2 ---------------> CHCl3+ HCl                  +Cl2 Properties- (1) colourless heavy liquid (2) sweet taste  (3) it is oxidised in the sunlight and form a harmful gas carbonyl chloride which is commonly called as phosgene.                     Sunlight 2CHCl3+O2 --------> 2COCl2 +HCl                                            Phosgene is a very poisonous gas. So it is not used in the anaesthetic purpose. Process of storage for chloroform- (1) For the prevent from sunlight chloroform is stored in coloured bottle. (2) for the prevent f

                     Alcohols Hydrocarbons are the parents of other organic compounds. When One or more hydrogen atoms are replaced by the different types of atoms or group of atoms from hydrocarbons then different types of organic compounds are formed .            When hydrogen atoms are replaced from saturated aliphatic hydrocarbons by the hydroxyl group (-OH) ,then Alcohols are formed.   For example-                 -H   R-H ------------->    R-OH                                +OH Where R is the alkAl group.                    -H  CH3-H ------------->     CH3-OH                         +OH              (Methanol) So, Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols. Classification of Alcohols- Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols. The general formula of the alcohols are R-OH. Where R is the Alkyl group. Alcohols are classified on the basis of the number of the Hydroxyl groups (-OH) attached to

Nomenclature of Haloalkanes The name of the haloalkanes are given by two different ways- (1)Trivial or common system- In this system haloalkanes are known as Alkyl halide.        There nomenclature are performed by the adding halide word in the given alkyl group. In this system the name of the compound is written in the two different words.    For example-     CH3-Cl          (Methyl chloride) CH3-CH2-Br     (ethyl bromide)                     Prifixes of the different types of alkyl group- (a) prefix- n The means of prefix-n is normal. This is used in the straight chain of the Alkyl group.  For example-  CH3-CH2-CH2-Br                          (n-propyl bromide) (b) prefix- iso Prefix-iso is used for those Alkyl group in which methyl (--CH3) branch is present in the last of the chain. For example- CH3-CH-Br          |          CH3   (Isopropyl bromide) (c) prefix- neo Prefix-neo is used for those Alkyl group in which two methyl (--CH3) gro

      Haloalkanes and Haloarenes Haloalkanes-  The word Haloalkane is made up by the two words, -          Halo = halogen          Alkane= Aliphatic hydrocarbon (containing single bond only) So, Haloalkanes are those compounds which is formed when a hydrogen atom replaced by any halogen atom from the alkanes.                - H    R-H  -------------->      R-X                 +X Where ,   R  =  Alkyl group               X  = Halogen ( F,Cl, Br, I) For example-                                  - H          CH3-H  --------------> CH3-Cl                            +Cl Haloarenes-  The word Haloarene is made up by the two words, -          Halo = halogen    Arene= Aromatic hydrocarbon So, Haloarenes are those compounds which is formed when a hydrogen atom replaced by any halogen atom from the arenes.                - H    Ar-H  -------------->      Ar-X                 +X Where ,  Ar  =  Aromatic hydrocarbon               X  = Halogen ( F,Cl, Br,

  Allotropes of carbon  The various physical forms in which an element can exist are called allotropes of the element. The carbon elements exists in three solid forms called allotropes. The three allotropes of the carbon are - (1) Diamond (2) Graphite (3) Buckminster fullerene               (1) Diamond Diamond is a colourless transparent substance having extraordinary shining. Diamond is quite heavy. Diamond is extremely hard. It is the hardest natural substance known. Diamond does not cunduct electricity. Diamond burns on strong heating to form carbon dioxide. If we burn diamond in Oxygen , then only CO2 gas is formed and nothing is left behind. This shows that diamond is made up of carbon only. Structure of Diamond -  A Diamond crystal is a very big molecule of carbon atoms. Each carbon atom in the diamond crystal is linked to four other carbon atoms by strong covalent bonds. The four surrounding carbon atoms are at the four vertices of a regular tetrahedro

        Newton's laws of motion Newton has given three laws to describe the motion of bodies. These laws are known as Newton's laws of motion. The Newton's laws of motion give a precise definition of force and establish a relationship between the force applied on a body and the state of motion acquired by it. Newton's first law of motion - Newton's first law describes the behaviour of such bodies which are in a state of rest or of uniform motion in a straight line.          According to Newton's first law of motion -  A body at rest will remain at rest, and a body in motion will continue in motion in a straight line with a uniform speed, unless it is compelled by an external force to change its state of rest or of uniform motion.     It should be noted that by saying an external force, we mean a force from outside the body.      Let us take some examples to make the first law of motion more clear.     Suppose a book is lying on the table. It is at res

                         Cell  Cell -   The cell is the fundamental unit of life. All plants and animals are made up of cells. Cell is the microcosm (having a definite boundary with in) which constant chemical activities and flow of energy proceed. Cell is the structural and functional unit of all organisms.       The body of an organism may contain one cell as in Unicellular organisms. Each cell has the capacity to perform all vital activities like nutrition, growth, respiration, irritability, movement and reproduction etc. Discovery of cell - The cell was discovered by the scientist Robert Hooke in 1665, when he worked on the wooden cork. He cut the thin slices of wooden cork and see these thin slices of cork in the self made microscope. Then he saw the honey comb like structures . These structures are called cell by the scientist Robert Hooke in 1665. **  The cell which is discovered by the scientist Robert Hooke was a dead cell.  ** The first living cell (B

Real images and virtual images  (1) Real images-   The image which can be obtained on a screen is called a real image .  In a cinema hall , we see the images of actors and actresses on the screen. So, the images on a cinema screen is an example of real images. A real image is formed when light rays coming from an object actually meet at a point after reflection from a mirror ( or refraction through a lens ). A real image can be formed on a screen because light rays actually pass through a real image. Real images can be formed by a concave mirror. A convex lens can also form real images. (2) Virtual images-  The image which cannot be obtained on a screen is called a virtual image . A virtual image can be seen only by looking into a mirror ( or a lens) . The image of our face formed by a plane mirror cannot be obtained on a screen, it can be seen only by looking into the mirror. So the image of our face in a plane mirror is an example of virtual image. Virtual images are

                    Ohm's law  Ohm's law gives a relationship between current and potential difference. According to Ohm's law -      At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its end.         If I is the current flowing through a conductor and V is the potential difference ( or voltage) across its ends,then according to Ohm's law -              I ~ V   ( At constant temperature)       or,  V~ I       or,   V =  R  ×  I Where R is a constant called       " resistance'' of the conductor.  The SI unit of resistance is ohm. The value of this constant depends on the nature, length,are a of cross - section and temperature of the conductor.                                       V          Resistance R = --------                                        I The above equation is a mathematical expression of Ohm's law.

        Apiculture ( Bee Keeping)  Bee keeping or Apiculture ( L. apis = bee, culture= cultivate ) is the rearing, care and management of honey bees for obtaining honey, wax and other substances. Honey is known to have medicinal value. It is found to be quite useful in the treatment of various disorders of human beings related to digestion, dysentery, vomiting and stomach or liver ailments.              Bee keeping being ,a low investment enterprise, has become a favourite source of some extra income for the  farmers .Bee keeping is also helps in cross pollination of flowers. Products obtained from Apiculture -  (1) Honey -   Honey is a sweet, viscous edible fluid containing sugars , water, minerals, vitamins, amino acids, enzymes and pollen. Sugars present in honey include levulose , dextrose, sucrose and dextrin. Minerals of honey are calcium, iron, phosphate and manganese. The colour,flav fla and odour of honey usually depends on the flowers from which nectar is gathered.

                       Acids * Acids are those compounds    which gives Hydrogen ions (H+ ion) in aqueous solutions. For example-        HCl --------> H+    +  Cl`        (aq)            (aq)       (aq) * Acids are those compounds which makes hydronium ions in aqueous solutions. For example-           HCl --------> H+    +  Cl`        (aq)            (aq)       (aq) H+  +   H2O ------->  H3O+                            (Hydronium ion) * Acids are those compounds which is reacts with bases and form salts and water. For example- NaOH  +  HCl -------> NaCl +H2O (Base)     (Acid)      (Salt)   (Water) * Acids are those compounds which are bitter in taste.    For example- citric acid , lactic acid etc. *Organic acids and mineral acids- (1) Organic acids-   The acids present in plant materials and animals are called organic acids.  For example- Acetic acid, formic acid etc. (2)Ino rganic acids-   The acids prepared from the

                  Force  When we want to open a door, we have to push the door handle. And when we want to close the door, we have to pull the door handle with our hands. This means that to move a body or an object, it has either to be pushed or pulled.           A push or pull on a body is called force. The direction in which a body is pushed or pulled is called the direction of force.         Forces are used in our everyday actions like pushing, pulling, lifting, stretching, twisting and pressing. For example - A force is used when we push (kick) a football.   Effects of force -       A force cannot be seen. A force can be judged only by the effects which it can produce in various bodies or objects around us . A force can produce the following effects -  1) A force can move a stationary body. 2) A force can stop a moving body. 3) A force can change the speed of a moving body. 4) A force can change the direction of a moving body. 5) A force can change the sha

        Dalton's atomic theory  The theory that all matters is made up of very tiny indivisible particles (atoms) is called atomic theory of matter. Dalton put forward his atomic theory of matter in 1808.       The various postulates or assumptions of Dalton's atomic theory of matter are as follows- (1) All the matter is made up of very tiny particles called atoms. (2) Atoms cannot be divided. (3) Atoms can neither be created nor be destroyed. (4) Atoms are of various kinds. There are as many kinds of atoms as are elements. (5) All the atoms of a given element are identical in every respect, having the same mass, size and chemical properties. (6) Atoms of different elements differ in mass, size and chemical properties. (7) Chemical combination between two or more elements consists in the joining together of atoms of these elements to form molecules of compounds. (8) The numbers and kind of atoms in a given compound is fixed. (9) During chemical combina

               The Gas law  (A) Boyle's law -  This law is given by the scientist Robert Boyle in 1662. According to this law-   The volume of a given mass of a gas is inversely proportional to its pressure provided the temperature remains constant.                                                                                 1  v     =   -----            ( at constant                     p          temperature )  Or,     pv =  k = constant Let the pressure and volume of any  gas is p   and V  and the                        1           1   pressure and volume    of the same  amount of the same gas be p  and v      then -  2           2     p   v    =   p    v  = constant       1    1         2    2  (B) Charles' law-    This law is given by the scientist J. Charles in 1787. According to this law- At constant pressure, the volume of a given mass of a gas is directly proportional to its absolute temperature.      V   ~  T  (at