Class 9 Science

Treatment or Prevention

  • Prevention is better than cure
  • How to prevent infections
    • By preventing exposure
    • Boosting the immune system
    • Vaccination

Prevention is Better Than Cure

Whenever a person suffers from infection, doctor gives suitable medicines to get rid of infection.

But treating the infection has certain limitations which are as follows:

  • An infection hampers the routine activity of a person for a few or many days. This often results in loss of work for that person. This can also result in loss of earning for the person.
  • An infection may result in short term or long term debility.
  • Treating a disease involves many costs; like cost of medicine, fees of doctor, cost of hospital stay, etc.
  • An infected person may become a source of infection for many other persons.

Hence, prevention is always better than cure. Prevention can help in ruling out most of the above costs which are associated with a disease.

How to Prevent Infections

By Preventing Exposure

Many diseases can be prevented by preventing the exposure against microbes.

Air borne disease can be prevented by some simple measures. If you are suffering from common cold then you should cover your face while sneezing or coughing. In case of a flu scare in the city, you should wear a face mask while going to a public place or traveling by public transport.

Water borne disease can be prevented by avoiding the use of contaminated water. You should always carry drinking water from home. If that is not possible then you should buy bottled water for drinking. Never buy food from those vendors who do not keep their food items covered. Don’t eat stale or spoiled food items.

Vector borne diseases can be prevented by preventing the breeding of vectors. If we can prevent mosquitoes from breeding around us, we can easily prevent malaria and dengue. Additionally, we should use mosquito repellants to prevent mosquito bite.

Pet dogs should be vaccinated against rabies. We should be careful of stray dogs as some of them may be infected with rabies.

We should not share clothes with a person who may be suffering from skin disease.

For preventing AIDS and hepatitis B, we should always use disposable syringe.

Boosting the Immune System

Whenever a pathogen enters our body, our immune system fights against that. We suffer from an infectious disease only when the microbes overpower our immune system. So, strengthening the immune system can help in preventing many diseases. This can be achieved by eating well balanced and nutritious diet. Our food should include all the necessary nutrients as well as vitamins and minerals.

The above methods of prevention are called general ways of prevention because they are not directed against any particular disease. But when a prevention method is directed against a particular disease, it is called the specific way of prevention. Vaccination comes under this category.


Vaccination is based on the principle that our body learns to fight against a certain microbe when the microbe attacks our body for the first time. Vaccines are made from dead or weak strains of a microbe. Vaccine is inoculated in the body in appropriate dose. After vaccination, the body learns to fight with that microbe. As a result, our body easily wards off any future onslaught of that microbe. Many diseases can be prevented by vaccines.

Small Pox

Small pox was a deadly disease in the nineteenth century. Edward Jenner was he scientist who developed vaccine against small pox.

Now-a-days, vaccines are available for many diseases. Example: Small pox, polio, whooping cough, tuberculosis, diphtheria, tetanus, Hepatitis B, rabies, etc.


See Answer

1: (a) Air borne disease, 2: (b) Water borne disease, 3: (d) Vaccine, 4: (c) Rabies, 5: (d) All of the above, 6: (a) Mosquito, 7: (d) All of the above, 8: (b) Small pox, 9: (a) Diphtheria, Pertussis, Tetanus, 10: (d) Tuberculosis

Matter in Our Surroundings

Anything that has both mass and volume is called matter. You can also say that anything which has mass and which occupies space is called matter.

Is Matter Around Us Pure?

Elements and compounds are pure substances. All other substances are mixtures which means they are not pure substances.

Atoms and Molecules

Read about law of conservation of mass, law of constant proportions and Dalton's atomic theory.

Structure of Atoms

Atom is made of three particles; electron, proton and neutron. These particles are called fundamental particles of an atom or sub atomic particles.

Cell: The Fundamental Unit of Life

A cell is capable of independent existence and can carry out all the functions which are necessary for a living being.


A groups of cells which is meant for a specific task is called tissue. Tissues are the first step towards division of labour in complex organisms.

Diversity in Living Organisms

Without proper classification, it would be impossible to study millions of organisms which exist on this earth.


If an object changes its position with respect to a reference point with elapse of time, the object is said to be in motion.

Force & Laws of Motion

Force has numerous effects. Force can set a stationary body in motion. Force can stop a moving body.


Earth attracts everything towards it by an unseen force of attraction. This force of attraction is known as gravitation or gravitation pull.

Work & Energy

When force is exerted on an object and object is displaced, work is said to be done. It means work is the product of force and displacement.


Sound is a type of energy. Sound travels in the form of wave from one place to another.

Why Do We Fall Ill

Health is a state of physical, mental and social well being. A condition in which the affected person is unable to carry out normal activities is termed as disease.

Natural Resources

Resources which are obtained from nature are called natural resources. Examples: Air, water, soil, wood, etc.

Improvement in Food Production

Food security is said to exist when all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life.