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 (conditions such as diabetes and asthma) 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: infections whose pathogens can pass between hosts directly or indirectly, such as flu, typhoid and dengue. Non-communicable diseases: conditions such as diabetes and asthma that are not passed from person to person. Their causes can include genetic, physiological, environmental and behavioural factors.

Deficiency diseases: caused by inadequate nutrients, for example scurvy from too little vitamin C. Some anaemia is due to iron deficiency and some goitre to iodine deficiency, but both have other possible causes. Chronic: lasting a long time; the textbook uses more than three months. Chronic does not mean non-infectious: some infections are chronic too.

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 used for certain bacterial infections; they kill susceptible bacteria or inhibit their growth. They do not treat viral colds or flu. Different infections require different medicines chosen by a clinician. 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?

ANSWERClimate change can alter the conditions in which mosquitoes, ticks and pathogens survive, shifting where some infections occur. Heat, flooding and disrupted water supplies can also affect health. It does not mean that warming automatically creates a new pathogen; local ecology, sanitation and healthcare also matter.

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

ANSWERPersistent stress can affect sleep, appetite, concentration and how the body feels. It may contribute to headaches or other health difficulties, but feeling worried does not automatically mean someone is ill.Supportive relationships, rest and talking with a trusted adult can help. If distress or physical symptoms persist or interfere with daily life, a counsellor or health professional can assess them; the textbook story is not enough to diagnose a real 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) The school should notify families, arrange safe care for unwell pupils, encourage staying home while ill, improve ventilation, support handwashing and cough etiquette, and follow local health advice on masks and gatherings.(ii) Speak kindly and help the classmate tell the teacher or school health staff. Offer notes or schoolwork while they recover; do not blame or ridicule them.(iii) Cover coughs with a tissue or elbow, wash hands, avoid sharing drinking bottles, improve indoor air and use a well-fitting mask when appropriate. Stay home when ill and follow school and health-authority return guidance. See CDC respiratory-virus precautions.

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 destination advice and consult a clinician about whether preventive malaria medicine is needed. During: use appropriate repellent as directed, covering clothes, screens and an insecticide-treated net where recommended. Take prescribed prevention for its full advised schedule, including after travel if instructed. After: fever during or after travel needs prompt medical assessment; tell the clinician where and when you travelled.(ii) Nets and repellents reduce mosquito bites, lowering the chance that an infected mosquito passes malaria parasites to us. They reduce risk rather than guaranteeing complete protection.(iii) Ignoring advice can lead to malaria and serious illness. An infected traveller may also contribute to transmission where suitable mosquitoes are present; malaria is not spread by ordinary casual contact.Reference: CDC malaria travel prevention.

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?

ANSWERVinita could ask: “Do antibiotics cure a viral cold or flu?” No. “Does every bacterial infection need the same medicine?” No; treatment depends on the infection. “Can resistant bacteria survive treatment?” Yes.These questions show why antibiotics are not a cure for every infection. Use them only when prescribed and follow the clinician’s instructions; do not share or reuse leftover medicine.

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: 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) In many parts of India, these months overlap the monsoon. Rain can fill containers with standing water, and warmth and humidity can favour mosquito survival and transmission. These are plausible explanations; this table alone cannot establish the cause or describe every region. (iv) Before the peak season: empty and scrub water-holding containers weekly, cover stored water, remove discarded tyres and litter, improve drainage and provide community education. Use screens, covering clothes and suitable repellent as directed. Aedes mosquitoes bite mainly during the day, so night-time nets alone are insufficient. Authorities should guide targeted mosquito control; fogging alone does not remove breeding sites.
Bar graph of textbook dengue cases: January 10, February 12, March 15, April 18, May 22, June 40, July to September 65 each, October and November 30 each, December 20.
Question 7: all 12 bars use the NCERT values. July, August and September tie for the maximum; January has the minimum. Tap to view at full size.

The data are a textbook exercise, not a current dengue surveillance report. Prevention reference: WHO dengue guidance.

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?

ANSWERAntibiotics act on susceptible bacteria, not the viruses that cause colds and flu. They therefore do not cure those viral infections; unnecessary use can cause side effects and select resistant bacteria.A cough is a symptom, not a disease caused only by viruses. Its cause and any need for treatment should be assessed appropriately. Reference: CDC antibiotic-use guidance.

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?

ANSWERDuring the first encounter, the adaptive immune system takes time to recognise the pathogen and build a specific response. Some activated lymphocytes become memory cells.On a later encounter with the same recognised antigen, memory cells can trigger a faster and often stronger response. Vaccination develops this protective memory without requiring the person to suffer the disease. Protection varies with the pathogen, vaccine and person, so it is not a guarantee that reinfection is impossible.The body also has immediate, general defences; “slow first response” does not mean it has no protection at first exposure.
First encounter activates a specific immune response and forms memory cells; a later encounter triggers a faster response.
How immune memory supports protection. This is a conceptual diagram, not a measured clinical timeline. Tap to view at full size.

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 do not treat viral colds or flu; suitable treatment depends on the infection.
  • Thinking vaccines treat a disease — vaccines are preventive, not curative.
  • Assuming all illness is caused by germs or unhealthy choices — genetics, nutrition, environment and other factors also matter.
  • Changing prescribed antibiotic treatment yourself or using leftovers — follow the clinician’s dose and duration, and seek advice about side effects or concerns.

Extra Practice Questions

These questions and MCQs are ClearStudy practice, separate from the NCERT exercise.

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: pathogens can spread between hosts directly or indirectly, for example typhoid through contaminated food or water. Non-communicable: the condition is not transmitted between people, for example diabetes. Causes can involve inherited, environmental and other factors.

Q2. How does a vaccine protect us from disease?

ANSWERA vaccine exposes the immune system to a harmless target, such as a weakened or inactivated pathogen, a component, or instructions for making a component. This develops a specific response and immune memory, helping protect against later disease. The vaccines discussed here prevent disease rather than treating an established illness.

Long Answer Type Question

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

ANSWERResistance: bacteria survive or grow despite an antibiotic that would normally act against them. It is the bacteria, not the person’s body, that become resistant.Development: resistance can arise through genetic changes or acquisition of resistance genes. Antibiotic exposure can select resistant bacteria, which then multiply and spread; unnecessary use increases this selection pressure.Prevention: use antibiotics when prescribed, follow the prescribed dose and duration, and ask the clinician before changing treatment. Do not share medicines or use leftovers. Infection prevention also reduces antibiotic need.

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 not transmitted from one person to another.

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 experienced by the person, whereas a sign can be observed or measured.

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 have varied causes, including genetic and environmental factors. Healthy habits can reduce many risks but do not prevent every case.
  • 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 are used for certain bacterial infections, 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 reduce the risk of type 2 diabetes and cardiovascular disease, while supporting general health. Using antibiotics only as prescribed keeps them effective against bacterial infections for the future.

How to write a clear answer

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 are used for certain bacterial infections and that vaccines are preventive. For data questions like the dengue graph, read values carefully and link the peak to the monsoon.

Further reading: WHO on non-communicable diseases and their wider causes. These are textbook explanations; individual treatment decisions belong with a qualified health professional.

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 transmitted between people (e.g. diabetes, asthma). Genetic, physiological, environmental and behavioural factors can contribute.

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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