NCERT Solutions for Class 9 Science Chapter 13 Why Do We Fall ill

NCERT Solutions for Class 9 Science (biology) Chapter 13 Why Do We Fall ill are given below. In these solutions, we have answered all the intext and exercise questions provided in NCERT class 9 science textbook. Class 9 NCERT Solutions Science Chapter 13 provided in this article are strictly based on the CBSE syllabus and curriculum. Students can easily download these solutions in PDF format for free from our app.

Class 9 Science Chapter 13 Textbook Questions and Answers


PAGE NO. 178

Question 1: State any two conditions essential for good health.

Answer: ‘Health’ is a state of being well enough to function well physically, mentally and socially. Therefore, for good health.
(i) One should be disease free. 
(ii) There should be social equality and harmony which are essential for individual health particularly for social and mental health.

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

Answer: The twoconditions essential for being free of diseases are:

(i) Personal hygiene and cleanliness are necessary to stay away from diseases.

(ii) Individuals should take a balanced diet that contains carbohydrates, fats, proteins, vitamins, fibres, and proper quantity of water.

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

Answer: No. The answers to the above questions may not necessarily be the same. This is because a disease free state is not the same as being healthy. Good health is the ability of an individual to realise his or her full potential. Individuals can have poor health without having any identifiable disease. Also, health is related to society and community, whereas having a disease is about an individual sick person. Hence, the conditions for good health and for being disease free can be same or even different.

PAGE NO. 180

Question 1: 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 not?

Answer: Common symptoms, which indicate sickness are:
(i) Headache,        
(ii) Cough and      
(iii) Loose motion.

Even seeing one symptoms. I will go to doctor.

Reason: A single symptom is the sign of a disease. On delaying, it may lead to serious illness.
For example, headache may mean meningitis.

Question 2: In which of the following case do you think the long – term effects on your health are likely to be most unpleasant?

  • If you get jaundice.
  • If you get lice.
  • If you get acne.  


Answer: Jaundice because it is a chronic disease and takes long time to be cured. Moreover, jaundice affects the whole body and it takes long time to be healthy.

PAGE NO. 186

Question 1: Why are we normally advised to tale bland and nourishing food when we are sick?

Answer: Infectious disease show a lack of success of the immune system of the body. For the functioning of immune system properly, sufficient nourishment and easily digestible food is necessary for a sick person.

Question 2: What are the different means by which infectious diseases are spread?

Answer: Diseases can be spread through various means such as air, water, sexual contact, blood, and vector.

(i) Certain disease-causing micro-organisms are expelled in air by coughing, sneezing, talking, etc. These micro-organisms can travel through dust particles or water droplets in air to reach other people. For example, tuberculosis, pneumonia, etc. spread through air.

(ii) Sometimes causal micro-organisms get mixed with drinking water and spread water borne diseases. Cholera for example is water borne disease.

(iii) Sexual act between two people can lead to the transfer of diseases such as syphilis, gonorrhoea, AIDS, etc.

(iv) Certain diseases such as AIDS can spread via blood to blood contact during blood transfusion or pregnancy.

(v) Certain diseases spread by animals called vectors. For example mosquitoes spread malaria.

Question 3: What precautions could you take in your school to reduce the incidence of infectious diseases?

Answer: Precautions to reduce incidence of infectious diseases are:

 (i) Preventing over crowing classes,
(ii) Providing safe drinking water,
(iii) Cleanliness in the school premises and also in the classroom,
(iv) Use of handkerchief or towel while an infected student in sneezing or coughing,
(v) Use of clean toilets,
(vi) Not to allows water to stagnate in school or around the school to avoid mosquito breeding,
(vii) To get vaccinated whenever programmers organized in the  for inoculation against  various diseases.
(viii) Not eating food exposed to flies, mosquitoes etc.

Question 4: What is immunization?

Answer: Introduction of mild type of infection (microbes) or killed infectious microbes into the body by vaccination / by other means to activate the immune system against a particular infection / disease is called immunization. 

Question 5:  What is the immunization programme available at the nearest health center in your locality?

Which of these diseases are the major health problems in your area?

Answer:  Immunization programme
(i) BCG vaccine against tuberculosis.
(ii) Polio drops against polio.
(iii) Vaccination against chicken pox.
(iv) Vaccination against Hepatitis.
(v) DPT vaccination against diptheria, pertusis (whooping cough) and tetanus.
(vi) Immunisation against measles.

Major health problems are (i) Hepatitis, (ii) Chicken pox, (iii) Tuberculosis, and (iv)


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

Answer: The illness was 2-3 times, common-cold, occurred in a year.
(a) One change I would make in my habits in order to avoid the above illness is that I would take a proper diet rich in vitamin C and would avoid too cold food.
(b) The surroundings should be neat, and clean,

Question 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?

Answer: A doctor/nurse/health worker when exposed to sick people they keep their nose and mouth covered, take care of hygiene, wash hands with soap before drinking water or eating food. They use mask, gloves, etc to avoid direct contact with the person suffering from infectious diseases.

Question 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 your local authorities to bring down the incidence of these diseases.

Answer: The following three are the most common diseases in any neighbourhood:
Cold and cough, loose motions, and malaria.
Some of the preventive measures that can be taken are:

(a) By drinking fresh, uncontaminated, and clean water.
(b) By maintaining hygienic-sanitary conditions.
(c) By educating people about various preventive measures with the help of posters, and pamphlets.

Question 4. A baby is not able to tell bis/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?

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

Question 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 is taking care of someone suffering from chicken-pox.
(c) When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox.

Answer: (c) When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox.

As the person is not taking a proper diet which is required for her proper health and healing of the body.
Her chances of getting chicken-pox also high as her body’s immunity have lowered.

Question 6. Under which of the 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.

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

A person can most likely fall sick when his/her friend is suffering from measles. It is a highly contagious disease and can easily be transferred through air and respiration. It is always better to stay away from your friend who is affected with measles, else even you may get infected with the disease.

Class 9 Science NCERT Solutions Chapter 13 Why Do We Fall ill?

CBSE Class 9 Science NCERT Solutions Chapter 13 helps students to clear their doubts and to score good marks in the board exam. All the questions are solved by experts with a detailed explanation that will help students complete their assignments & homework. Having a good grasp over CBSE NCERT Solutions for Class 9 Science will further help the students in their preparation for board exams and other competitive exams such as NTSE, Olympiad, etc.

NCERT Solutions for Class 9 Science Chapter 13 PDF

Below we have listed the topics discussed in NCERT Solutions for Class 9 Science Chapter 10. The list gives you a quick look at the different topics and subtopics of this chapter.

Section in NCERT BookTopics Discussed
13.1Health and its Failure
13.2Disease and Its Causes
13.3Infectious Diseases
13.3.4Principles of Treatment
13.3.5Principles of Prevention

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