NCERT Class 9 Science Solutions: Chapter 13 Why Do We Fall Ill –Part 1

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Q 1 Image Showing Healthy And Infected Person.

Q 1 Image Showing Healthy and Infected Person

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Question 1:

Q. State any two conditions essential for good health.


The two conditions essential for good health are:

  • An individual must have better health facilities and more professionals to deal with health problems.

  • All basic necessary conditions to prevent diseases must be present. For example, proper garbage collection and disposal, clearing of drains, supply of healthy drinking water, etc.

Question 2:

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


The two conditions 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:

Q. Are the answer to the above questions necessarily the same or different? Why?


No. The answers to the above questions may not be necessarily being the same. This is because a disease frees state in not the same as being healthy. Good health is the ability of an individual to realize 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.

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 or why not?


Symptoms such as a headache, stomach pain, nausea, vomiting, fever, etc. make us feel that we are sick and must visit a doctor. These symptoms basically indicate that there might be a disease, but we cannot predict the kind of disease. Therefore, it becomes necessary to visit a doctor so that the disease can be identified and can be treated with proper medication.

However, if only one of these symptoms is present, we usually do not visit a doctor. This is because such symptoms do not have much effect on our general health and ability to work. However, if a person is experiencing these symptoms for quite sometime, then he needs to visit a doctor for proper treatment.

Question 2:

Q. 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



Jaundice is a disease that can cause long-term effects on our health. It is a chronic disease that lasts for a long period of time. Jaundice does not spread rapidly, but it develops slowly over a period of time.

Question 1:

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


We are normally advised to consume bland and nourishing food when we are sick so that we can get the nutrients and energy quickly to fight off the foreign disease causing agents.

Question 2:

Q. What are the different means by which infectious diseases are spread?


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, Gonorrhea, 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.