SANJEEV KUMAR RAI

 PURE SUBSTANCE : A substance having one types of atoms or molecules  is called a pure substance. A pure substance is either an element like carbon and hydrogen or a compound like salt and sugar . EXAMPLES: oxygen, hydrogen ,  carbon , gold , silver, etc. all chemical compounds such as water sait, sugar, etc. PROPERTIES OF A PURE SUBSTANCE: * It cannot be separated into two or more substances by physical or mechanical manner. *It is homogeneous.It means that it has uniform compositions throughout the whole sample. *It has definite chemical composition. *It has definite properties like melting point or boiling point. IMPURE SUBSTANCES: Impure substances are commonly called mixtures. In other words, a mixture or an impure substance is made up of two or more substances. The difference substances present in a mixture are called its components or constituents. mixtures are the substances held together by physical forces known as intermolecular forces. EXAMPLE:sea water is a mi...

  Discovery of magnets Magnets were probably discovered by greeks about 2500 years ago. According to a legend, a shepherd boy named magnes living in greece. One day he noticed that the iron tip of his stick got stuck to a large black Rock. This black Rock was named magnetite after magnes. It is also said that magnets were first discovered in magnesia.        What are magnets?  A magnet is a material that attracts iron objects having iron.  Magnetic material Materials that get attracted towards a magnet are called magnetic materials. E. g. Iron, nickel, cobalt.  Non-magnetic material Materials which do not  get attracted towards a magnet are called non-magnetic materials. E. g wood, cotton, leather, plastic, etc.         Types of magnets Naturally occurring magnets are natural magnets. E. g magnetite.  Considering the usefulness  of magnets, they are now made artificially. Artificial magnets are man-made by u...

  Alphabet reasoning Alphabet:(capital letters)  A B C D E F G H I J K L M N O P Q R S T U V W X Y Z.  Alphabet:(small letters)  a b c d e f g h i j k l m n o p q r s t u v w x y  z.  Position of alphabet letters: A B C D E F G H I  J   K   L   M  N  O  P  Q   R  1 2  3 4  5 6 7  8 9 10 11 12 13 14 15 16 17 18 S    T     U    V    W    X   Y    Z 19  20   21  22  23    24  25  26 Opposite letters: A    B   C    D    E    F   G   H    I     J   K   L   M !      !     !     !     !     !    !     !     !    ...

    RESPIRATION Living organisms take in oxygen present in the air. This process of taking in oxygen is called breathing.  The process of taking in oxygen and its oxidation to release energy is called respiration.  Respiration by Animals Humans breathe in air through the nostrils into the lungs. Animals living in water like fish, have gills to separate  the dissolved oxygen from water.  1) Humans breathe through lungs.  2) Fish breathe through gills.  3) Earthworms breathe through their body surface.  Respiration in plants Plants get oxygen from the environment and return carbon dioxide and water vapour into it. Generally, plants do not have any organs for breathing. In plants, the exchange of gases takes place through small pores on the surface of their leaves known as stomata. 

  Elements are classified as metals and non-metals.  Metals are mostly solids, lustrous, have high density, good conductor of heat and electricity, malleable, ductile and tenacious.  Mercury is a liquid metal.  Metals lose electrons to form cations.  Non-metals  usually have properties contrary to metals. They usually form acidic oxides.  Metals activity series K>Na>Ca>Mg>Al>Zn>Fe>Pb>[H]>Cu>Hg>Ag>Pt>Au. 1) metals below hydrogen cannot displace hydrogen from acids.  2) metals above hydrogen can displace it from dilute acids.  3) The higher the position, the more active is the metals.  Minerals from which metals may be extracted economically are called ores.  Heating of ore in the presence of air is called roasting.  Heating of ore in the absence of air is called calcination.  The process of reducing the roasted ore is called smelting.  Refining of metals can be carried by distilla...

  Life processes Life processes are the vital processes carried out by living organisms in order to maintain and sustain life.  The molecular movement are essential to carry out the various life processes such as nutrition, respiration, excretion, growth and repair and reproduction.  Nutrition This energy is obtained from carbon-based food source through the process called nutrition.  AUTOGRAPH:plants prepared their own food. That is why plants are called autotrophs. This mode of nutrition is called autotrophic nutrition.  HETEROTROPHS:Animal and Non-green plants depend directly or indirectly on green plants for their food. This method of nutrition is called heterotrophic.  Photosynthesis * The process of synthesis of glucose with the help of carbon dioxide and water in the presence of sunlight.  *The process of synthesis of food by green plants is called photosynthesis.  The green leaves contains a pigment called  C hlorophyll.  A cross...

FOOD AND NUTRITION AUTOTROPHS:Animals are dependent on plants for their food.But plants prepare their own food.That is why plants are called autotrophs and this mode of nutrition is called autotrophic nutrition. The process by which leaves make food for the plant is called photosynthesis. animals depend directly or indirectly on green plants for their food.This method of nutrition is called heterotrophic nutrition and animals and non-green plants are called heterotrophs. GROWTH Growth means increase in size of an organisms. human beings grow up to the age of 16 to 20 years. a seed germinates and grows into a complete plant. 

            living thing   living thing;the things that have life in them are called living thing. feature of living thing; 1.living thing move. 2.living thing grow. 3.livin thing breathe. 4.living thing reproduce. 5.living thing eat and drink. 6.living thing feeling. plants,insects,animals,human beings are suchexample of living thing.                       non-living thing The things that do not have life in them are called non-living thing. feature of non-living thing ; 1.non-living thing not move 2.non-living thing not grow  3.non-living thing not breathe 4.non-living thing not reproduce 5.non-living thing not eat and drink. 6.non-living thing not feeling. glass,paper,plastics,rock,wood are such example of non-living thing. characteristics of living thing:- 1.cellular structure; cell are the basis building blocks of the life. a british scientist robert hooke  discovered the cell in the...

 Important  Questions 1.In a certain code, "TOMATO" is written as "ATOMTO ".How is " POTATO "is written in the code?  Ans:APOTTO, ATOTTO.  2.In a certain code, " CUP"is written as "DVQ".How is " CAT" is written in the code?  Ans:DBU. 3.If white is called blue, blue is called red, red is called black, black is called green, green is called yellow, what would be the colour of human hair?  Ans:🟢Green. 4.The opposite letter of 'de'                                     ans;wv                 5.the opposite letter of abc ans;zyx. 6. Addition alphabet; ABC+MZX =A=1,B=2,C=3+M=13,Z=26,X=24 =123+486 =609 =6+0+9 =15 =O.