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9th Class

Is Matter Around us Pure

  Is Matter Around us Pure   Synopsis  
  • Chemistry deals with the study of matter. The matter around us is of two types: pure substances and mixtures.
 
  • A pure substance is homogeneous in nature and has a definite set of properties. The composition of pure substances cannot be changed by physical methods. Pure substances can be further classified as elements and compounds.
 
  • Elements: Pure substances in which molecules are composed of only one kind of atoms are called elements, e.g., silver, iron, oxygen, nitrogen, etc.
 
  • Compounds: Pure substances in which two or more elements combine chemically in a fixed proportion by weight are called compounds. For example, water (H,0) is considered as a pure substance even more...
Catgeory: 9th Class

Notes - Atoms and Molecules

  Atoms and Molecules   Synopsis    
  • The simplest form of matter which can neither be split into nor built up from two or more dissimilar substances is called an element.
 
  • An atom of an element is denoted by the symbol of that element.
 
  • An atom of an element also denotes the atomic mass possessed by that element.
 
  • Each atom of an element is characterised by its atomic number and mass number.
 
  • Atomic weight of an element in grams is called gram atomic weight or gram atom.
 
  • The smallest part of a substance that can exist independently is called a molecule.
 
Catgeory: 9th Class

Structure of the Atom

  Structure of the Atom   Synopsis  
  • Atoms are the building blocks of all matter. The word atom, meaning indivisible was coined by Greek philosopher Democritus. Scientists, then assumed that these are the smallest units of matter. The first theory about atom was put forward by Dalton.
 
  • Atom contains fundamental particles electrons, protons and neutrons.
 
  • Thomson's Model of an Atom
          (a) It is also known as water melon model or plum pudding model.          (b) Electrons are embedded in the positively charged mass distributed uniformly thoughout the atomic sphere.  
  • Demerits
 
  • It could not explain how both positive and negatively charged particles protect their identity being together.
 
  • Rutherford bombarded a - particles at very high speed to more...
Catgeory: 9th Class

Cell

  Cell - The Fundamental Unit of Life   Synopsis  
  • The cell is the basic unit of life. Cells were first discovered by Robert Hooke in 1665 by the observation of a cork slice under microscope. The cell theory was proposed by Schleiden and Schwann.
 
  • Rudolf Virchow proposed that all cells originate from pre-existing cells. The outermost covering that separates the contents of the cell from its external environment is called the plasma membrane, which is selectively permeable and is made up of lipids and proteins.
 
  • Plant cells have a rigid outer covering in addition to the plasma membrane. It is called the cell wall and is composed of cellulose.
 
Catgeory: 9th Class

Tissues

  Tissues   Synopsis  
  • A group of cells that are similar in structure and work together to perform a particular function is called a tissue
                    
  • Most of plant tissues that are supportive are dead but provide mechanical strength whereas most of the animal tissues are living. Plant tissues can be classified as meristema tic and permanent tissues Meristema tic tissues are classified as apical (tip of stem and roots), lateral (girth of stem and root), intercalary meristems (internodes).
 
  • Cells formed by meristema tic tissue lose the ability to divide and form a permanent tissue, which is termed as differentiation
 
  • Permanent tissues, which consist of similar types of cells are called simple permanent tissues Parenchyma, collenchyma and sclerenchyma are more...
Catgeory: 9th Class

Diversity in Living Organisms

  Diversity in Living Organisms   Synopsis  
  • Classification helps us in exploring the diversity of life forms and systematic study of organisms.
 
  • Robert Whittaker (1959) proposed the '5-kingdom System' based on the cell structure, mode of nutrition and body organisation. The five kingdoms are Monera, Protista, Fungi, Plantae and Animalia.
 
  • Scheme of classification is:
          Kingdom \[\to \] Phylum (or) Division \[\to \] Class \[\to \]Order\[\to \] Family \[\to \] Genus \[\to \] Species.  
  • Monerans do not have a defined nucleus. The mode of nutrition is either autotrophic or heterotrophic. e.g., cyanobacteria, mycoplasma, etc.
 
  • Protista includes unicellular eukaryotic organisms mode of nutrition is either autotrophic or heterotrophic. e.g., diatoms, protozoan, etc.
    • more...
Catgeory: 9th Class

Health and Diseases

  Health and Diseases   Synopsis  
  • Health is a state of complete physical, mental and social well-being and not merely an absence of disease.
 
  • Basic conditions required for good health include balanced diet, personal hygiene, clean food, water and air, exercise, no addictions and good economic conditions.
 
  • Health is influenced by genetic, environmental, economic status and psychological factors.
 
  • A sign of a disease is a change in the bodily function or structure that can be observed, e.g., rashes, swelling or glands, change in colour of the skin, etc.
 
  • Depending upon the duration of diseases, they are classified into acute and chronic diseases.
 
Catgeory: 9th Class

Improvement in Food Resources

  Improvement in Food Resources   Synopsis  
  • Food supplies all the required nutrients for the development, growth and health of the body.
 
  • Cereals like wheat, provide carbohydrates, pulses (grams) provide proteins and oil seeds provide fats.
 
  • Hybridization is the crossing between genetically dissimilar plants.
 
  • Improvement of agriculture is done for higher yield, biotic and abiotic resistance, improved quality grade, adaptability and other factors.
 
  • Macronutrients are those that are required in large quantities by the plants (N, R K, Ca, Mg,S, etc.).
 
  • Micronutrients are those that are required in small quantities (Mn, B, Zn, etc.).
 
  • Manure contains organic matter and supplies nutrients more...
Catgeory: 9th Class

Natural Resources

  Natural Resources   Synopsis  
  • Life on earth depends on resources like soil, water, air and energy from the sun.
 
  • The outer crust of the earth is called the lithosphere.
 
  • The air that covers the earth like a blanket is called the atmosphere. It prevents the sudden increase in temperature during daytime.
 
  • The life supporting zone on earth is known as the biosphere. Living things constitute the biotic components and non-living things constitute the abiotic components of biosphere.
 
  • The hot air released from various biological activities consists of water vapour that can expand and cool. This cooling causes it to condense and form rain.
 
Catgeory: 9th Class

Work and Energy

  Work and Energy   Chapter Overview  
  • Introduction
  • Definition of Work
  • Measurement of work done by a content force
  • Nature of work
  • Unit of work
  • Energy
  • Different forms of energy
  • Kinetic energy
  • Relation between kinetic energy and linear momentum
  • Potential energy
  • Definition of potential energy
  • Types of potential energy of a system
  • Potential energy of an object at a height
  • Transformation of energy
  • Conversion of potential energy into kinetic energy and then in electrical energy
  • Devices used to transform energy from one form to another
  • Law of conservation of energy
  • Power
  • Average in terms of energy
  • Power in terms of energy
  • Commercial unit of energy
 
  • Introduction
    • The concept of work is related to the concept of more...
    Catgeory: 9th Class

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