Class 9 Science Notes – Let’s Revise!

Class 9 Science Notes:

We have consolidated some highlights of basic scientific knowledge in the following Class 9 Science Notes. Let us look at these class 9 science notes and revise our understanding of the subject.

Matter in Our Surrounding

• Anything that has mass, volumes and can be comprehended by the senses is matter.
• Matter is created from very small particles that can be seen by a microscope (AFM).
• Matter has kinetic energy that intensifies with an increase in temperature.
• When particles of two or more materials intermingle on their own it is known as diffusion. .
• There are five states of matter
  • Solid
  • Liquid
  • Gas
  • Plasma
  • Bose-Einstein Condensate
• Solid state is attained when the particles are firmly packed together and vibrate only in their fixed positions. Kinetic energy is low.
• The kinetic energy of atoms in liquids is more than of solids.
• The kinetic energy of atoms in gases are loose enough for them to break free from any boundaries, they are not restricted and can move about in an arbitrary motion.
• Plasma is the fourth state and they have super active and super energized atoms in the form of ionised gases.
• The Bose-Einstein condensates are created when a gas of low density is frozen and the atoms break down into a single quantum state.

Is matter around us pure?

• In terms of matter, as per scientists the best way to determine if a substance is pure or not is to take a part of that substance from one portion and compare it to another part of that very substance obtained from another random portion. They should match and there should be no discrepancy.
• One can say that a pure substance is that which is made of a single element or only one kind of molecules.
• Pure substances are divided into elements and compounds.
• Elements can be grouped as metals, non – metals and metalloids.
• If a substance is made up of different kinds of elements or molecules it is known as impure.
• Impure substances are known as a mixture. Mixtures can be homogenous or heterogeneous.
• Heterogenous mixtures can further be divided into suspensions, colloids and Tyndall Effect.

Atoms and Molecules

• The process of combining two or more elements to form new compounds is governed by the laws of chemical combination, they are of two types
  • Law of conservation of mass
  • Law of constant proportion
• Dalton’s atomic theory states that all matter is composed of small particles called atoms.

Structure of the Atom

• There are three fundamental particles of an atom. The proton, electron and neutron.
• The Electron was discovered by J.J. Thomson by conducting a cathode ray experiment.
• Proton was discovered by Ernest Goldstein by the Canal Rays experiment.
• Neutron was discovered by J. Chadwick.
• Thomsons Model of Atom states that atom is electrically neutral.
• Bohr’s Model of Atom states that there is a heavily charged nucleus. The electrons revolve around it in an orbit.

Image Credits: Who Invented First

The Fundamental Unit of Life

• Cell Theory states that all living organisms are made up of cells.
• A cell is the structural and the functional unit of life.
• It was discovered by Robert Hooke.
• There are unicellular organisms and there are multicellular organisms.
• There are prokaryotic cells and eukaryotic cells. The first is devoid of the nucleus and the second has it.
• The cell is made up of the
  • cell wall,
  • membrane,
  • nucleus and
• The plasma membrane is permeable and substances can pass through by
  • Diffusion
  • Osmosis – solutions exhibiting osmosis
    • Hypnotic solution
    • Hypertonic solution

Image Credits: National Cancer Institute

Tissues

• A group of cells that have similar shape and function are known as tissues. Multiple tissues form an organ.
• There are four basic types of tissues
  • Epithelial Tissue- formed by cells that cover the external part of the body organs.
  • Connective Tissue – these give shape to the organs and holds them in place.
    • fibrous connective tissue,
    • fluid connective tissue,
    • skeletal connective tissue.
  • Muscular Tissue- involved in producing force and generating muscles.
    • Skeletal muscle
    • Cardiac muscle
    • Visceral or smooth muscle
  • Nervous Tissue – the main tissue component of the brain and the spinal chord.
• There are three tissue systems for plants
  • Epidermis tissues
  • Vascular tissues
  • Ground Tisssues
• There are two types of plant tissues
  • Meristematic tissues
    • Apical Meristem
    • Lateral Meristem
    • Intercalary Meristem
  • Permanent Tissues
    • Simple Permanent Tissues
    • Complex Permanent Tissues
    • Secretory Tissues

Gravitation

• Every object in the universe attracts another object by a force of attraction which is directly proportional to the product of masses of the objects and inversely proportional to the square of the distance between them.

• When an object free falls its acceleration changes due to the gravitational force, this is known as acceleration due to gravity (g). Unit ms⁻²

Work and Energy

• The force acting upon an object to cause displacement is known as work. W=f(force)x s(displacement). Unit – joule
• The capacity of a body to do work is known as energy. Unit – joule
• There are various kinds of energy
  • Kinetic energy

• Potential energy- E_p = mgh,
  • Gravitational potential energy
  • Elastic potential energy
• The time rate of doing work is power. Power= work/time. Unit joule/s

Natural Resources

• That which cannot be made but collected from nature. Eg. Water, coal, iron.
• There are two types
  • renewable natural resources
    • fossil fuel
    • air
  • non-renewable natural resources

Image Credits: Eschool Today

It is important to partake in the conservation of natural resources as they are getting exhausted at an alarming rate besides having an adverse reaction to the environment. These class 9 science notes will help you get through your subjective questions in exam.