Class 8 Science Curiosity Chapter 3 Solutions (NCERT 2026–27) – Health: The Ultimate Treasure

These Class 8 Science Curiosity Chapter 3 solutions cover Health: The Ultimate Treasure from the new NCF-2023 textbook (2026–27), with every “Keep the curiosity alive” question solved step by step.

Class: 8 Subject: Science Book: Curiosity Chapter: 3 Exercise: Keep the curiosity alive (11 Qs) Session: 2026–27
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Class 8 Science Curiosity Chapter 3 Solutions – Overview

Chapter 3 of Curiosity, Health: The Ultimate Treasure, explains that health is a state of complete physical, mental and social well-being – not merely the absence of disease (the WHO definition). It shows how a healthy lifestyle and a clean environment keep us well, the difference between signs and symptoms, and how diseases are grouped into communicable (caused by pathogens that spread) and non-communicable (lifestyle, deficiency and chronic) diseases. It covers how communicable diseases spread (air, water/food, vectors), immunity, vaccines, antibiotics and the growing problem of antibiotic resistance. These Class 8 Science Curiosity Chapter 3 solutions answer every textbook question accurately and in exam-ready language.

Key Concepts & Definitions

Health: a state of complete physical, mental and social well-being, not just the absence of disease (WHO).

Disease: a condition that affects the normal working of the body or mind. Pathogens are disease-causing organisms – bacteria, viruses, fungi, worms or protozoa.

Symptom vs sign: a symptom is what we feel (pain, tiredness); a sign is what can be seen or measured (fever, rash, high blood pressure).

Communicable diseases: caused by pathogens and spread from person to person (typhoid, dengue, flu, chickenpox, COVID-19). Non-communicable diseases (NCDs): not caused by germs and do not spread (cancer, diabetes, asthma); linked to lifestyle, diet and environment. Deficiency diseases (scurvy, anaemia, goitre) and chronic diseases (lasting more than 3 months) are non-communicable.

Vectors: insects such as mosquitoes and houseflies that carry pathogens. Immunity: the body’s natural ability to fight diseases, through the immune system.

Vaccine: trains the immune system to recognise and fight a germ, giving acquired immunity; preventive, not curative. Antibiotics: medicines that kill bacteria; they do not work against viruses or protozoa. Antibiotic resistance: bacteria surviving and multiplying despite antibiotic treatment.

“Probe and ponder” — Answers

How does your body respond to an infection such as common cold?

ANSWERThe immune system reacts to the invading virus. We may get fever, a runny nose, coughing and sneezing — these are the body’s ways of fighting and removing the germs. The immune cells attack the pathogen and we usually recover in a few days.

We rarely see cases of smallpox or polio these days, but diseases like diabetes and heart problems are more common. Why?

ANSWERSmallpox and polio are communicable diseases that have been controlled by vaccination (smallpox is eradicated). Diabetes and heart problems are non-communicable diseases linked to changing lifestyles — processed food, less exercise and longer lives — so they are now more common.

Could climate change lead to new types of diseases?

ANSWERYes. Warmer, wetter conditions can spread vectors like mosquitoes to new areas, increasing diseases such as malaria and dengue, and may help new pathogens emerge or old ones spread further.

How do emotions like stress or worry affect us and make us sick?

ANSWERHealth includes mental well-being. Long-term stress or worry can cause headaches, poor sleep, weight loss and a weaker immune system, making us fall ill more easily — as seen in Activity 3.1 about the lonely student.

Why do some groups of people get affected more than others during disease outbreaks?

ANSWERPeople with weaker immunity, poor nutrition, crowded or unhygienic surroundings, less access to clean water, vaccines or healthcare, or existing illnesses are more vulnerable and so get affected more during outbreaks.

Class 8 Science Curiosity Chapter 3 Solutions — Keep the Curiosity Alive

1. Group the diseases shown in the images as communicable or non-communicable. Cold and flu   Typhoid   Diabetes   Asthma   Chickenpox

ANSWER
Communicable (spread by pathogens)Non-communicable (lifestyle/other)
Cold and flu, Typhoid, ChickenpoxDiabetes, Asthma
Cold/flu, typhoid and chickenpox are caused by germs and spread from person to person, so they are communicable. Diabetes and asthma are not caused by germs and do not spread, so they are non-communicable.

2. Diseases can be broadly grouped into communicable and non-communicable diseases. From the options given below, identify the non-communicable diseases. (i) Typhoid   (ii) Asthma   (iii) Diabetes   (iv) Measles (a) (i) and (ii)   (b) (ii) and (iii)   (c) (i) and (iv)   (d) (ii) and (iv)

ANSWER (b) (ii) and (iii) — asthma and diabetes are non-communicable. Typhoid and measles are caused by pathogens (bacteria and virus) and spread, so they are communicable.

3. There is a flu outbreak in your school. Several classmates are absent, while some are still coming to school coughing and sneezing. (i) What immediate actions should the school take to prevent further spread? (ii) If your classmate, who shares the bench with you, starts showing symptoms of the flu, how can you respond in a considerate way without being rude or hurtful? (iii) How can you protect yourself and others from getting infected in this situation?

ANSWER (i) Ask sick students to stay home and rest; advise masks; ensure handwashing with soap and provide sanitiser; improve ventilation; clean shared surfaces; spread the disease to fewer people by avoiding large gatherings or assemblies until it is under control. (ii) Be kind — gently suggest they wear a mask, cover their mouth and nose while coughing or sneezing, wash their hands, and rest at home until they feel better. Offer to help them inform the teacher, instead of teasing or avoiding them rudely. (iii) Wash hands often, wear a mask, do not share water bottles, food or stationery, cover your own mouth and nose when coughing/sneezing, keep a little distance, and stay home if you feel unwell.

4. Your family is planning to travel to another city where malaria is prevalent. (i) What precautions should you take before, during, and after the trip? (ii) How can you explain the importance of mosquito nets or repellents to your sibling? (iii) What could happen if travellers ignore health advisories in such areas?

ANSWER (i) Before: check health advisories, carry mosquito repellent, nets and long-sleeved clothes, and consult a doctor about preventive medicine. During: use nets and repellents, wear full-sleeved clothes, avoid areas with stagnant water at dusk/night. After: watch for fever, chills or sweating and see a doctor at once if symptoms appear. (ii) Tell them simply: malaria is spread by the bite of an infected mosquito, so a net while sleeping and repellent on the skin stop mosquitoes from biting and keep us from falling sick. (iii) They could be bitten by infected mosquitoes and catch malaria (high fever, chills, sweating), fall seriously ill, and even spread the infection to others through mosquitoes when they return.

5. Your uncle has started smoking just to fit in with his friends, even though it is well known that smoking can seriously harm health and even cause death. (i) What would you say to him to make him stop, without being rude? (ii) What would you do if your friend offers you a cigarette at a party? (iii) How can schools help prevent students from indulging in such harmful habits?

ANSWER (i) Calmly tell him that you care about him; explain that smoking damages the lungs and heart and raises the risk of cancer, so real friends would not want him to harm himself. Suggest healthier ways to relax and offer to support him in quitting. (ii) Politely but firmly say “No, thank you”, explain that it harms health, and walk away. A true friend will respect my choice; I should never feel pressured to fit in. (iii) Schools can run awareness programmes and talks by doctors, teach about the harms of tobacco and alcohol, encourage sports and hobbies, enforce a no-tobacco rule on campus, and offer counselling support.

6. Saniya claims to her friend Vinita that “Antibiotics can cure any infection, so we don’t need to worry about diseases.” What question(s) can Vinita ask her to help Saniya understand that her statement is incorrect?

ANSWER Vinita can ask, for example: “Do antibiotics work against viral infections like the common cold or flu?” (they do not), “Can antibiotics cure non-communicable diseases such as diabetes or asthma?” (they cannot), and “What happens if we take antibiotics carelessly?” (bacteria develop antibiotic resistance). These questions show that antibiotics only kill certain bacteria, not all infections.

7. The following table contains information about the number of dengue cases reported in a hospital over a period of one year: Jan 10, Feb 12, Mar 15, Apr 18, May 22, Jun 40, Jul 65, Aug 65, Sep 65, Oct 30, Nov 30, Dec 20. Make a bar graph of the number of cases on the Y-axis and the month on the X-axis. Critically analyse your findings and answer the following: (i) In which three months were the dengue cases highest? (ii) In which month(s) were the cases lowest? (iii) What natural or environmental factors during the peak months might contribute to the increase in dengue cases? (iv) Suggest a few preventive steps that the community or government can take before the peak season to reduce the spread of dengue.

ANSWER Bar graph (described): draw months Jan–Dec along the X-axis and cases (0–70) along the Y-axis. Each bar height = the value above. The bars rise from January, peak in July–September (65 each), then fall.
MonthCasesMonthCases
January10July65
February12August65
March15September65
April18October30
May22November30
June40December20
(i) Cases were highest in July, August and September (65 cases each). (ii) Cases were lowest in January (10 cases). (iii) The peak months are the monsoon season — rain leaves stagnant water in which mosquitoes breed, plus warm and humid weather, so the dengue-carrying Aedes mosquito population rises. (iv) Before the peak season: remove stagnant water from coolers, pots, tyres and drains; spray/fog to control mosquitoes; supply mosquito nets and repellents; run awareness drives; cover water storage; and clean surroundings regularly.

8. Imagine you are in charge of a school health campaign. What key messages would you use to reduce communicable and non-communicable diseases?

ANSWER For communicable diseases: “Wash your hands with soap”, “Cover your mouth and nose while coughing or sneezing”, “Drink clean/boiled water and eat properly cooked food”, “Get vaccinated”, and “Stay home when sick”. For non-communicable diseases: “Eat a balanced diet, avoid junk food and sugary drinks”, “Stay physically active and play outdoors”, “Limit screen time and get enough sleep”, and “Say NO to tobacco and alcohol”. A combined message: Prevention is better than cure.

9. It is recommended that we should not take an antibiotic for a viral infection like a cold, a cough, or flu. Can you provide the possible reason for this recommendation?

ANSWER Antibiotics kill bacteria by targeting parts of bacterial cells; colds, coughs and flu are caused by viruses, which have a different structure, so antibiotics have no effect on them. Taking antibiotics needlessly does not cure the viral illness and instead encourages bacteria to develop antibiotic resistance, making the medicines less effective in future.

10. Which disease(s) among the following may spread if drinking water gets contaminated by the excreta from an infected person? Hepatitis A, Tuberculosis, Poliomyelitis, Cholera, Chickenpox.

ANSWER Hepatitis A, Poliomyelitis and Cholera spread through water contaminated with the excreta of an infected person. Tuberculosis and chickenpox spread mainly through the air (respiratory route), not contaminated water.

11. When our body encounters a pathogen for the first time, the immune response is generally low but on exposure to the same pathogen again, the immune response by the body is much more compared to the first exposure. Why is it so?

ANSWER On the first exposure, the immune system takes time to recognise the new pathogen and build defences, so the response is slow and low. During this, the body forms memory cells that “remember” the pathogen. On the next exposure, these memory cells recognise the germ at once and act faster and more strongly, giving a much stronger immune response. This is also why vaccines work — they create this memory in advance.

Common Misconceptions to Avoid

Watch out for these

  • Thinking health means only “not being sick” — it includes physical, mental and social well-being.
  • Confusing a sign with a symptom — a symptom is felt (pain); a sign can be seen or measured (fever, rash).
  • Believing antibiotics cure all infections — they kill only bacteria, not viruses or protozoa.
  • Thinking vaccines treat a disease — vaccines are preventive, not curative.
  • Assuming all diseases are caused by germs — non-communicable and deficiency diseases are not.
  • Stopping an antibiotic course early or taking it without a prescription — this breeds antibiotic resistance.

Extra Practice Questions

Very Short Answer Type Questions

Q1. Define a pathogen.

ANSWERA pathogen is a disease-causing organism, such as a bacterium, virus, fungus, worm or protozoan.

Q2. What are vectors? Give two examples.

ANSWERVectors are insects that carry and spread pathogens from one person to another, for example mosquitoes and houseflies.

Q3. Who discovered the first vaccine, and against which disease?

ANSWEREdward Jenner discovered the first vaccine, against smallpox, using cowpox material.

Short Answer Type Questions

Q1. Differentiate between communicable and non-communicable diseases with one example each.

ANSWERCommunicable diseases are caused by pathogens and spread from person to person, e.g. typhoid. Non-communicable diseases are not caused by germs and do not spread; they are linked to lifestyle, diet or environment, e.g. diabetes.

Q2. How does a vaccine protect us from disease?

ANSWERA vaccine contains dead, weakened or harmless parts of a germ. It trains the immune system to recognise and attack that germ and to form memory cells, so if the real pathogen attacks later, the body fights it quickly — this is acquired immunity. Vaccines are preventive, not curative.

Long Answer Type Question

Q1. What is antibiotic resistance? Explain how it develops and how it can be prevented.

ANSWER Antibiotic resistance is when bacteria that were once killed by an antibiotic survive and multiply despite treatment with it. How it develops: taking antibiotics when they are not needed, in the wrong dose, or not completing the course allows a few naturally resistant bacteria to survive. These multiply and can even pass resistance to other bacteria, and resistant bacteria can spread through people, hospitals, food and the environment. Prevention: use antibiotics only when prescribed by a doctor, in the correct dose, and complete the full course; never use them for viral illnesses or in animals unnecessarily; and maintain good hygiene to prevent infections in the first place.

MCQs & Assertion–Reason

1. According to the WHO, health is:

(a) only the absence of disease    (b) complete physical, mental and social well-being    (c) only physical fitness    (d) being free from injury

2. Which of the following is a non-communicable disease?

(a) typhoid    (b) dengue    (c) diabetes    (d) chickenpox

3. Malaria is caused by a:

(a) virus    (b) bacterium    (c) protozoan    (d) worm

4. Which disease spreads through contaminated water and food?

(a) cholera    (b) tuberculosis    (c) measles    (d) chickenpox

5. Antibiotics are effective against:

(a) viruses    (b) bacteria    (c) all pathogens    (d) non-communicable diseases

6. The natural ability of the body to fight diseases is called:

(a) infection    (b) immunity    (c) symptom    (d) resistance

7. A sign of being unwell is:

(a) pain    (b) tiredness    (c) fever (measured temperature)    (d) dizziness

8. Insects like mosquitoes and houseflies that spread pathogens are called:

(a) parasites    (b) vectors    (c) hosts    (d) pathogens

9. Edward Jenner developed the first vaccine against:

(a) polio    (b) tetanus    (c) smallpox    (d) cholera

10. Diseases that last for more than three months are called:

(a) acute diseases    (b) chronic diseases    (c) deficiency diseases    (d) communicable diseases

Answer key: 1-(b), 2-(c), 3-(c), 4-(a), 5-(b), 6-(b), 7-(c), 8-(b), 9-(c), 10-(b).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: Vaccines are preventive and not curative.

Reason: A vaccine trains the immune system to fight a germ before infection happens.

A-R 2. Assertion: Antibiotics should not be taken for the common cold.

Reason: The common cold is caused by a virus, against which antibiotics are ineffective.

A-R 3. Assertion: Diabetes is a communicable disease.

Reason: Diabetes is caused by pathogens that spread from person to person.

A-R 4. Assertion: Dengue cases often rise during the monsoon season.

Reason: Stagnant rainwater provides breeding sites for mosquitoes that spread dengue.

A-R 5. Assertion: A symptom and a sign are the same thing.

Reason: A symptom is something a doctor can measure, like body temperature.

Answer key: 1-(A), 2-(A), 3-(D), 4-(A), 5-(D).

Quick Revision Summary

  • Health means complete physical, mental and social well-being — not just the absence of disease. Health and happiness are closely related.
  • A disease affects the normal working of the body or mind. Symptoms are what we feel; signs are what can be seen or measured.
  • Non-communicable diseases (diabetes, heart disease) are caused by lifestyle and environment, not germs, and can often be prevented by healthy habits.
  • Communicable (infectious) diseases are caused by pathogens — bacteria, viruses or worms — and spread by air, water/food or vectors.
  • The immune system protects us; vaccines train it using dead, weakened or harmless parts of a germ to prevent disease.
  • Diagnosis and treatment matter; antibiotics work only on bacteria, and their misuse causes antibiotic resistance.

Real-life Applications

This chapter guides daily life: washing hands with soap, drinking boiled/clean water and eating properly cooked food prevents cholera, typhoid and hepatitis; removing stagnant water and using nets and repellents controls malaria and dengue; getting vaccinated protects against polio, measles and tetanus; and a balanced diet, exercise, sleep and saying NO to tobacco help prevent diabetes, obesity and heart disease. Using antibiotics only as prescribed keeps them effective against bacterial infections for the future.

How to score full marks in this chapter

Memorise the WHO definition of health and the exact difference between a sign and a symptom. Be ready to classify any disease as communicable or non-communicable with its cause and mode of spread. Remember that antibiotics work only on bacteria and that vaccines are preventive. For data questions like the dengue graph, read values carefully and link the peak to the monsoon.

Frequently Asked Questions

What is Class 8 Science Curiosity Chapter 3 about?

Chapter 3, Health: The Ultimate Treasure, explains what health means (physical, mental and social well-being), how to stay healthy, signs versus symptoms, communicable and non-communicable diseases, immunity, vaccines, antibiotics and antibiotic resistance.

What is the difference between communicable and non-communicable diseases?

Communicable diseases are caused by pathogens and spread from person to person (e.g. typhoid, dengue, flu). Non-communicable diseases are not caused by germs and do not spread; they are linked to lifestyle, diet and environment (e.g. diabetes, asthma).

How many questions are in the “Keep the curiosity alive” exercise of Chapter 3?

There are 11 questions, all solved on this page along with the “Probe and ponder” prompts.

Are these Class 8 Science Curiosity Chapter 3 solutions free?

Yes. All solutions are free and follow the official NCERT Curiosity textbook for 2026–27.

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