is matter around us pure class 9 notes

 

             is matter around us pure class 9 notes

Pure : Pure means that there is no mixing in a substance. A pure substance is made up same kind of elements .

Example :  Water, gold

Mixture : It constitute two of more substance is any proportion .

Example : Air is mixture of oxygen, nitrogen, carbon dioxide , tea

                                           Mixture 

·       Homogeneous

·       Heterogeneous

Homogeneous: These mixture has no visible boundaries of a separation between substance. It is in uniform composition. Example - sugar in water, salt in water

Heterogeneous: These mixture has visible boundaries of separation between substances. It is non uniform composition. Example : sand in water , chalk in water .

Solution: Solution is a homogeneous mixture of two or more substance .Example: sugar solution, salt solution

Solution has a two component.

·       Solute

·       Solvent

Solute : The substance that is added to the solvent to form a solution is called a Solute. For Example, Salt, when mixed in water, acts as a solute for the mixture

Solvent : The substance in which another substance is mixed is called the Solvent. For Example, Water is a solvent in which we can mix different substances such as salt or sugar.

   

Properties of solution  ( True Solution )

•    The size of solute particle are smaller  10 ^-9
•    Solute particles cannot seen by naked eyes
•    Particle do not scatter a beam of light
•    Path of beam light not visible in solution
•    Stable solution
•    Not show the tyndall effect 

C    Concentration of solution

 Dilute solution: Solution that contain less amount of solute is called     dilute solution .

  Concentrated solution: solution that contain high amount solute is  called concentrated.

   Saturated solution: When no more solute can be dissolved in solution at given temperature then is is called saturated solution. Saturation of solution increase when temperature increases.

    Suspension : A suspension is a heterogeneous mixture in which solute particle do not dissolve but remain suspended  but remain suspended.  Example : muddy water, chalk in water , milk of magnesia , paints etc.

                                 Properties of Suspension

• Size of solute partical are big
• Can be seen by naked eyes
• Particle scatter a beam of light
• Path of beam light visible in suspension
• May of may not show tyndall effect
• Unstable solution.

  

 

 

fundamental unit of life class 9 notes |cell || class 9 science chapter 5 notes

         fundamental unit of life class 9 notes

Cell Definition  :  

A Cell is defined as the smallest , basic unit of the life that is responsible for all of life's process . 

" Cell are structural , functional and biological unit of all living beings . They are called building blocks of the life " 

Robert hooke was the first Biologist who discovered cells in 1665. 

Discovery Of Cells : 

Robert Hooke discovered the cell in 1665 . Robert hooke observed a piece of bottle cork under a compound microscope and noticed tiny  structure that reminded him of small rooms.

Role of cells :  They provide structure to the body and convert the nutrients taken form the food into energy. 

fundamental unit of life

Characteristic of cells 

• Cell provide structure and support to the body of an organism.
• Every cell has one nucleus and membrane  bound organelles .
• Cell store hereditary information .

Types of Organisms on the Basis of Number of Cells

All organisms are made up of cells.

• Unicellular Organisms  :  The organisms which are made up only one cell.
• Mulitcellular Organisms  ; The organisms which are made up of many cells. Example - human being, animals 

Types of Cells :

Cells are similar to factories with different labourers and departments that work towards a common objective , various types of cells perform different function  based on cellular structure , there are two types of cells .

1. Prokaryotes
2. Eukaryotes

Prokaryotes	Eukaryotes
·         Have no nucleus. ·         They are single celled microorganisms. ·         The size range  is between  .01 to .05 nano meter ·         Cell division by binary fission .	·         Have a true nucleus. ·         They are multicelullar microorganisms. ·         The size of cell range between 10- 100 nano meter. ·         Plasma membrane is responsible for monitoring the transport of nutrients in and out of the cell. ·         Cell division by mitosis or meiosis.

Cell Structure ;

The cell structure comprises individual components with specific  function essential to carry out life process. These component include cell wall , cell membrane , cytoplasm , nucleus, and cell organelles .

Cell Membrane

Cell membrane is outer covering  of a cell, is also called plasma membrane . Cell membrane support and protect the cells .It control the movement of substance in and out of the cells. It is selectively permeable in nature.

Cell Wall:

The cell wall is the most prominent part of the plant's cell structure .it is made of cellulose , hemicellulose .It protect the plasma membrane. It provide shape and support to the cells.

It is absent in animal cell. Also help in transport of various substances in and out of the cell.

Nucleus:

• It sends signal to the cells to grow mature , divide and die.
• The nucleus contains the hereditary material of the cell the DNA.
• Nucleus is surrounded by nuclear envelop that separate the DNA from the rest of the cells.
• It was discovered by Robert Brown in 1831.
• It control all the metabolic activates of the cell.
• 
  

Cell

Cytoplasm :

The cytoplasm is a thick clear jellly like substance present inside the cell membrane .

Most of the chemical reactions within a cell take place in this cytoplasm. It dissolves cellular wastes.

Cell Organelles:

Cell organelles are specific  structure  present inside a particular type of cell that perform specific function .There are numerous cell organelles . 

Nucleolus :

The nucleolus is the site of ribosome synthesis , also it is involved in controlling cellular activities and cellular reproduction .  Nucleolus contain RNA. 

Chromosomes :

Chromosome play a crucial role in determining the sex of an individual. Each human cells contain 23 pairs of chromosome .Chromosome found only eukaryotic animal cells. 

Endoplasmic Reticulum:

Endoplasmic reticulum is involved in the transportation of substances throughout the cells. It play a primary role in the metabolism of carbohydrates Synthes of lipids, steroids and proteins . It also help in membrane propagation. It is absent in Prokaryotic cell. 

Endoplasmic reticulum are two types  

(i) Smooth reticulum 

(ii) Rough  reticulum

Golgi Apparatus :

Golgi bodies are the cell's post office as it is involved in the transportation of material within the cell. It was discovered by Camilo Golgi. It is absent in Prokaryotic cell. It involved in the formation of the lysosomes.

Mitochondria :

The power house of the cell. It is called so because it produce ATP. The cell energy currency.  Rod shaped organelles .Mitochondria have two membrane covering.

class 9 gravitation notes | Universal law of Gravitation | gravitation|| whats gravity | gravitation class 9 notes

                                   Gravitation Class 9 Notes

Gravitational Force :    Every object in this universe attract every other object with a certain force .
The force with which two object attract each other is called gravitational force .

Gravitational force is a non contact force .

> The strength of the gravitational attraction between two object     depends on  two factors 

• How big the object are
• How far apart they are 

                      Universal law of Gravitation 

Given by newton also known as newton's law of gravitation ,  Everybody in the universe attract every other body with a force which is directly proportional to the product of their masses and inversely proportional to the squire of the distance between them 

 .

                     GM₁M₂

_{F =                 __________}

                                R²

where G is the universal gravitation constant.

Value of G = 6.673*10-11Nm2Kg-2 

Gravitational force

                  Importance of Universal law of Gravitation 

• It bind us to the earth 
• It is responsible for the motion of the moon around the earth 
• It is responsible for the motion of planets around the sun 
• Gravitational force of moon causes tides in the sea  on earth .

• 
  

  

  class 9 gravitation notes 

  
  

Free Fall:     The falling of a body or object from height towards the earth under  gravitational force of earth ( with no other force acting on it ) and such a body is called freely falling body.

   Acceleration due to Gravity (g) :

The uniform acceleration produced in a freely falling body due to gravitational force of the earth is known as acceleration due to gravity.

Value of acceleration due to gravity is 9.8 m/s²

> g does not depends on the mass of the falling object of smaller mass . 

Calculation of acceleration due to gravity ( g) - 

 

F= mass * acceleration 

F= ma = GM₁M₂

_{_____________________________}

                R²

 ^{acceleration came due to the gravity of the earth} 

                 g     =       GM

                          _________

                                   R²

 

   G   g = 6.67x10^-11 x  6 x 10²⁴

_______________________                      = 9.8 m/s²

                (6.4 x 10⁶)²

The three equation of motion

Equation of motion	Motion due to gravity
·         v= u +at    ·          S = ut + ½ at2    ·         v2- u2 = 2as	·         v= u +gt   ·          S = ut + ½ gt2 ·         v2- u2 = 2gs

>  When a body is falling vertically downwards its velocity is increasing. So the acceleration          due to gravity is taken as positive    

.                     g  =  + 9.8 m/s²

 

^>  When a body is thrown vertically upwards  its velocity is decreasing . So the acceleration            due to gravity is taken as negative    

                     g  =  - 9.8 m/s²

 

> If an object is just drop or fall  from a height then  u = 0

Difference between Mass and Weight 

Mass	Weight
·         Actual content present in a body ·         Mass is always constant ·         Mass is never zero or negative ·         SI unit  = Kg	·         It is the force exert by the body on earth. ·         Weight is variable  ( change from place to place ) ·         Weight = mass * acceleration ·         Weight can be zero. ·         SI unit = N ( newton)

Gravity on moon is 1/6 less than the earth 

                                                         gravity on earth

      Gravity on moon   =              __________________

                                                                    6

Frictional Force : The force which always opposes the motion of one body over another body is called frictional force .

structure of atom |structure of atom class 9 notes | atomic model structure of atom class 9 notes

                                  Structure of the Atom           

  An Atoms contain three basics particles  namely  Proton, neutrons, and electorns .The nucleus of atoms contain Proton and neutrons, where Proton are positively charged  and neutrons are neutral .The electrons located at the outermost Regine called electron shall . 

Structure of Atoms 

Electron : JJ Thompson discovered  negatively charged sub-atomic particles  electron , emmited by the Cathode towards the anode in the cathode ray experiment , these negitvaly charged particles are electrons. 

Protons : Eugen Goldstein discovered that with a different condition in the same chamber Anode emitted  positively charged particles known as canal ray or later name as protons.

Neutron : J. Chandwick ,discovered a sub - atomic particle with no charge and a mass equivalent to proton in the nucleus of all atoms.These nuterally charged particles are neutrons .

structure of atom class 9 notes

Thompson Model of an Atom :- According to the Thompson   an atoms consist of a positively charged sphere and the electrons are embedded in it . 

ii)- The negative and positive charges are equal in magnitude , so the atom as a whole is electrically neutral. 
Thompson atomic model is compared to Watermelon, where he considered seeds as negatively charged particles and red part of the watermelon as positively charged. 

      Limitation of Thompson's model :

> Thompson structure of an atom failed to explain the arrangement of protons and electrons in its structure.

> Also failed to explain stability of atoms.

                            Rutherford's model of an atom : -  

Rutherford conduct an experiment and  Bombarding the alpha particles on a gold foil . He observed the path of the alpha particles after passing through an atom and drafted some postulate.

> Most of the space in an atom is empty as the particles passed through the gold foil without and hindrance .

Rutherford's Model of an atom

> The positively charged center is called the nucleus and the mass of an atom reside in the center.

> The particles deflected 180 degree after bombarding the nucleus.

> The size of the nucleus is small compared to the total size of the atom.

> Positive and negative charges balance with each other

Drawbacks of the Model :      

> The electrons revolve in an unstable path and they undergo acceleration energy, when the electron revolve they lose energy. Soon electron would collapse into the nucleus 

> The tendency would make an atom highly unstable while the atoms is highly stable .

>It also failed to explain the atomic number concept as it explained only presence of protons in the nucleus .

              Bohr's Model of an Atom 

To overcome of drawbacks of Rutherford  Neil Bohr proposed modified model of structure of atom.

> Electrons revolve around the necleus in stable orbits without emission of radiant energy. 

> Each orbit has a definite energy and is called an energy shell or energy level.

> An orbit is designated a K,L,M,N shell when the electron is in the lowest energy level it is said to be in ground state .

> An electron absorbe energy when it jumps from one orbit to another .

Orbit : orbits are the energy shell surrounding the nucleus in which electrons revolve