NCERT Solutions for Class 9 Science Chapter 13 Why do we Fall Ill

Chapter Name

NCERT Solutions for Class 9 Science Chapter 13 Why do we Fall Ill

Topics Covered

  • NCERT Intext Questions
  • NCERT Exercise Solutions

Related Study

  • NCERT Solutions for Class 9 Science
  • NCERT Revision Notes for Class 9 Science
  • Important Questions for Class 9 Science
  • MCQ for Class 9 Science
  • NCERT Exemplar Questions For Class 9 Science

NCERT Intext Questions

1. State any two conditions essential for good health.


Two conditions essential for good health are :

  1. State of physical, mental and social well-being.
  2. Healthy environment.

2. State any two conditions essential for being free of disease.


The two conditions essential for being free of disease are :

  1. Personal hygiene.
  2. Clean environment.

3. Are the answers to the above questions necessarily the same or different? Why?


The answer to the above questions are not same because a person may be free of disease but it is not necessary that his mental, social or economical health may be good.

4. List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor? Why or why not?


There are three reasons to think that he is sick are (1) headache, (2) cold and cough, (3) loose-motions. This indicates that there may be a disease but does not indicate the name of disease. So, one would visit the doctor for the diagnosis and treatment. Even in case of single symptom one needs to go to the doctor to get proper treatment.

5. In which of the following case do you think the long- term effects on your health are likely to be most unpleasant?
a. If you get jaundice
b. If you get lice
c. If you get acne


Lice and acne are acute problems of our health which can be cured in short duration. But jaundice is the disease that can have adverse effect on our health as it affects the liver. This disease is a chronic one.

6. Why are we normally advised to take bland and nourishing food when we are sick?


We are advised to take bland and nourishing food when we are sick because our body needs energy to release cells to overcome the infection, the wear and tear of body organ. The nourishing food provides nutrients to our body that will further provide energy and make new cells. No spices in the food makes its digestion process faster, does not release acids in thebody that can interfere in the treatment and cure.

7. What are the different mean by which infectious diseases are spread?


The different means by which infectious diseases spread are :

  1. Air : Common cold, influenza, tuberculosis, etc. diseases are air borne diseases, which can spread by little droplets thrown by sneezing or cough in air.
  2. Food and water : Contaminated food/water that contains bacteria, cause diseases like cholera, hepatitis.
  3. Physical contact : Many diseases spread by contact of infected person with the healthy person. Example : Fungal infections, skin diseases, scabies, etc.
  4. Sexual contact : Many diseases can be transmitted through sexual contacts. Example : Syphilis, AIDS.
  5. Vectors : The organism that spreads a disease from a patient to the host, is called vector. Example : Mosquitoes are vectors that carry pathogens like protozoa.

8. What precautions can you take in your school to reduce the incidence of infectious diseases?


The precautions that one can take in school to reduce the incidence of infectious diseases are :

  1. Using handkerchief while coughing and sneezing.
  2. Washing hands before eating.
  3. Staying at home during infectious diseases.
  4. Clean school surroundings and toilets.

9. What is immunization?


When the body attains immunity against any disease by vaccination, is called immunization.

10. What are the immunization programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?


Immunization programmes :

  1. Vaccination against smallpox.
  2. BCG vaccination against tuberculosis.
  3. Polio vaccination against polio.
  4. Vaccination against chicken pox.
  5. (v) Vaccination against hepatitis.
  6. (vi) DPT vaccination against tetanus, diphtheria, cough Chicken pox, Tuberculosis and Tetanus are the major health problems.

NCERT Exercises Solutions

1. How many times did you fall ill in the last one year? What were the illnesses?
(a) Think of one change you can make in your habits in order to avoid any of the above illnesses.
(b) Think of one change you would wish for in your surroundings in order to avoid any of most the above illness.


I suffered from cough and cold twice and malaria once.
(a) Change in Habits : I should avoid the company of persons suffering from cold and cough and not eating uncovered food. I will wear clothes suitable to protect from mosquito bites.
(b) Change in Surroundings :

  1. I will try to improve sanitary conditions in the surroundings.
  2. I will try to get drains cleaned regularly and kept covered not allowing water to collect near the houses to avoid mosquito breeding.

2. A doctor/nurse/health worker is exposed to more sick people than others in the community. Find out how she/he avoids getting sick herself/ himself?


A doctor/nurse/health worker when exposed to sick people :

  1. By keeping their nose and mouth covered.
  2. By taking care of their hygiene.
  3. Wash hands with soap before drinking water or eating food.
  4. Use mask, gloves, etc. to avoid the direct contact with the person suffering from infectious diseases.

3. Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by bring down the incidence of these diseases.


Common diseases are dysentery, malaria, viral and fever.

  1. Proper diet and avoid too cold food.
  2. Clean surrounding.
  3. Safe drinking water.
  4. Personal hygiene.
  5. Stop stagnation of water.

4. A baby is not able to tell his/her caretakers that she/he is sick. What would help us to find out?
(a) That the baby is sick?
(b) What is the sickness?


(a) The symptoms like body temperature, fever, cough, cold, loose-motions, non-stop crying improper or no food intake, etc. would help us to find that the baby is sick.
(b) The symptoms could help us to find out the sickness of the body.

5. Under which of the following conditions is a person most likely to fall sick?
(a) When she is recovering from malaria.
(b) When she has recovered from malaria and taking care of someone suffering from chickenpox. (c) When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox. Why?


(c) When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox. The functioning of the immune system will not be good in lack of proper and sufficient food.

6. Under which of following conditions are you most likely to fall sick?
(a) When you are taking examinations.
(b) When you have travelled by bus and train for two days.
(c) When your friend is suffering from measles. Why?


(c) When your friend is suffering from measles, as it is an infectious disease.

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