13 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 42, Q1
Group the diseases shown in the images as communicable or non-communicable: cold and flu, typhoid, diabetes, asthma, chickenpox.
Hint. Ask of each one: is a pathogen responsible?
Apply the single test — is it caused by a pathogen? If one is, the disease can pass from person to person, so it is communicable.
| Disease | Pathogen? | Group |
|---|
| Cold and flu | Yes — virus | Communicable |
| Typhoid | Yes — bacteria | Communicable |
| Diabetes | No | Non-communicable |
| Asthma | No | Non-communicable |
| Chickenpox | Yes — virus | Communicable |
Communicable: cold and flu, typhoid, chickenpox. All three appear in Table 3.1 with a causal agent — cold and flu and chickenpox spread through the air, typhoid through contaminated water and food.
Non-communicable: diabetes and asthma. Neither is caused by a germ, and neither can be caught from another person. The chapter names both as examples of diseases "linked to lifestyle, diet, and/or environment".
A caution about asthma. It involves coughing and breathing difficulty, which can make it look like an infection. But you cannot catch asthma from someone who has it — air pollution can trigger it, which is an environmental cause, not a transmissible one.
✦ Answer: Communicable — cold and flu, typhoid, chickenpox (all caused by pathogens); Non-communicable — diabetes, asthma (linked to lifestyle, diet and environment).
21 markCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 43, Q2
From the options below, identify the non-communicable diseases: (i) Typhoid (ii) Asthma (iii) Diabetes (iv) Measles. Choose (a) (i) and (ii), (b) (ii) and (iii), (c) (i) and (iv), (d) (ii) and (iv).
Hint. Two of the four are caused by pathogens listed in Table 3.1.
Check each against Table 3.1:
| Disease | Causal agent | Type |
|---|
| (i) | Typhoid | Bacteria | Communicable |
| (ii) | Asthma | None | Non-communicable |
| (iii) | Diabetes | None | Non-communicable |
| (iv) | Measles | Virus | Communicable |
The non-communicable ones are (ii) and (iii).
✓ Option (b)
Why the distractors are wrong. Options (a), (c) and (d) each include typhoid or measles, and both of those appear in Table 3.1 with a named pathogen — typhoid caused by bacteria and spread through contaminated water and food, measles caused by a virus and spread through the air. Anything with a causal agent in that table is communicable.
✦ Answer: (b) (ii) and (iii) — asthma and diabetes.
34 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 43, Q3
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? (ii) If your benchmate starts showing flu symptoms, how can you respond considerately without being rude or hurtful? (iii) How can you protect yourself and others?
Hint. Flu spreads through the air — every answer should follow from that one fact.
(i) What the school should do. Flu is spread by an infected person coughing or sneezing, so the measures must interrupt airborne and contact spread:
- Ask students who are unwell to stay at home and rest until they recover — this both helps them recover and minimises spreading the disease
- Tell everyone to cover the mouth and nose when coughing or sneezing, and provide masks for crowded indoor spaces
- Ensure soap and water are available and encourage frequent hand-washing
- Keep classrooms well ventilated, and clean shared surfaces
- Tell students not to share personal items such as handkerchiefs, towels, bottles or food
- Inform parents so unwell children are kept at home rather than sent in
(ii) Responding to your benchmate. Be kind and practical rather than accusing. Quietly offer a mask or tissue, suggest they tell the teacher and go to the school nurse, and offer to share your notes so they do not worry about missing lessons. Move a little distance away without making a display of it. The framing that works is "you'll get better faster if you rest" rather than "stay away from me" — it is true, it comes from the chapter, and it is not hurtful.
(iii) Protecting yourself and others. Wash your hands with soap frequently, avoid touching your face, do not share personal items or food, wear a mask in crowded places, cover your own mouth and nose when you cough or sneeze, and stay home yourself if you develop symptoms.
✦ Answer: (i) send unwell students home, insist on covering mouth and nose, masks, hand-washing, ventilation and no sharing of personal items; (ii) respond kindly and practically — offer a mask, suggest the nurse, offer notes, and frame resting as helping them recover; (iii) wash hands, avoid sharing, wear a mask, cover coughs, and stay home if symptoms appear.
44 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 43, Q4
Your family is travelling to a city where malaria is prevalent. (i) What precautions should you take before, during and after the trip? (ii) How would you explain the importance of mosquito nets or repellents to your sibling? (iii) What could happen if travellers ignore health advisories?
Hint. Malaria is caused by a protozoan and carried by a mosquito — so the whole answer is about avoiding bites.
(i) Precautions.
Before: find out about the malaria situation and any health advisory for that city; consult a doctor about preventive medication; pack mosquito nets, repellents and long-sleeved clothes.
During: sleep under a mosquito net; apply repellent on exposed skin; wear long-sleeved clothes and full-length trousers, especially at dawn and dusk; keep windows screened or closed; avoid places with still water, where mosquitoes breed.
After: watch for symptoms — high fever, profuse sweating and periodic chills — for some weeks after returning, since malaria may not appear immediately. See a doctor promptly if they occur, and mention where you travelled.
(ii) Explaining it to a sibling. Keep it concrete: malaria is not in the air, it is inside a mosquito. The mosquito has to bite you to pass it on. A net and repellent simply stop it reaching your skin — so no bite, no malaria. Naming the mechanism makes the precaution obviously worth the bother, which a rule alone does not.
(iii) If advisories are ignored. Travellers may catch malaria, with high fever, sweating and chills, and may become seriously ill. They may also carry the infection home, where local mosquitoes can pick it up and pass it on — so ignoring an advisory risks not just the traveller but their community. And delayed treatment makes the illness harder to manage.
✦ Answer: (i) before — check advisories, consult a doctor, pack nets and repellents; during — nets, repellents, long sleeves, avoid still water; after — watch for fever, sweating and chills and see a doctor; (ii) explain that the disease travels inside the mosquito, so blocking the bite blocks the disease; (iii) travellers may fall seriously ill and carry the infection home to spread locally.
54 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 43, Q5
Your uncle has started smoking to fit in with friends. (i) What would you say to make him stop, without being rude? (ii) What would you do if a friend offers you a cigarette at a party? (iii) How can schools help prevent students from such harmful habits?
Hint. The chapter's advice is a single line: say 'NO' to tobacco, alcohol and addictive drugs.
(i) Talking to your uncle. Speak from concern rather than judgement, and give him a reason rather than a rebuke:
- Say you care about him and want him around for a long time
- Point out that the chapter's own list of healthy living puts saying 'NO' to tobacco alongside diet, exercise and sleep — it is that basic
- Mention that Kamal Ranadive's research showed that tobacco raises the risk of cancer, so this is established evidence, not opinion
- Note that the reason he started — fitting in — is not a reason to continue, and that real friends will not require it
- Offer practical help: suggest he talk to a doctor, since stopping is genuinely hard and support works better than willpower alone
(ii) If a friend offers you a cigarette. Refuse clearly and without embarrassment — "No thanks, I don't smoke" is enough, and needs no justification. You can change the subject or move away. If you are pressed, say plainly that you know what it does to health. Deciding in advance what you will say makes it far easier than deciding in the moment.
(iii) What schools can do. Teach clearly why these substances are harmful rather than only forbidding them; invite doctors to speak; run awareness campaigns and student-led activities; provide counsellors students can approach without fear — as the school in Activity 3.1 did; encourage sport and other activities that provide belonging without harmful habits; and enforce a tobacco-free campus.
✦ Answer: (i) speak out of concern, cite the evidence that tobacco raises cancer risk, point out that fitting in is not a reason to continue, and offer to help him get support; (ii) refuse clearly and without apology — 'no thanks, I don't smoke'; (iii) schools should explain the reasons, invite doctors, provide counsellors, offer alternative activities and keep campuses tobacco-free.
64 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 43, Q6
Saniya tells Vinita: "Antibiotics can cure any infection, so we don't need to worry about diseases." What questions can Vinita ask to help Saniya see that this is incorrect?
Hint. The claim contains two separate errors — ask about each.
Saniya has made two mistakes, and good questions will expose them one at a time.
Questions about the first error — antibiotics do not work on everything:
- "Antibiotics kill bacteria by attacking parts of bacterial cells. So what do you think they do to a virus, which isn't even made of a cell?"
- "When you had a cold last month, did the doctor give you an antibiotic? Why not?"
- "Malaria is caused by a protozoan and ascariasis by worms — would an antibiotic help either?"
- "What about diabetes or asthma? Nothing infected the person — what would an antibiotic even do?"
Questions about the second error — even against bacteria, antibiotics are not permanently reliable:
- "Have you heard of antibiotic resistance? What happens when bacteria survive the antibiotic that used to kill them?"
- "If we take antibiotics whenever we like, will they still work when we really need them?"
- "Why do doctors insist on finishing the full course rather than stopping when you feel better?"
And one question about the conclusion itself:
- "If we can always be cured, why did the world bother to eradicate smallpox by vaccination instead of just treating it?" — which brings out that prevention is better than cure, and that vaccines are preventive, not curative.
What Saniya should end up seeing. Antibiotics work only against bacterial infections; they are useless against viruses, protozoa, worms and all non-communicable diseases; and misuse breeds resistance, which makes even bacterial infections harder to treat.
✦ Answer: Vinita should ask what antibiotics do to viruses, protozoa, worms and non-communicable diseases — nothing, since they target bacterial cell structures — and what antibiotic resistance is and what causes it, showing that misuse makes them stop working even against bacteria.
75 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 44, Q7
Dengue cases reported over a 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. Draw a bar graph with cases on the Y-axis and month on the X-axis. (i) Which three months were highest? (ii) Which month(s) lowest? (iii) What natural or environmental factors during the peak months might contribute? (iv) Suggest preventive steps before the peak season.
Hint. Look at when the peak falls in the Indian year.
Drawing the graph. Months along the X-axis in order, cases on the Y-axis with a scale to 70 (say, 10 per division). Twelve bars of equal width and equal spacing, each drawn to its value, with both axes labelled and the graph titled.
| Month | Cases | | Month | Cases |
|---|
| January | 10 | | July | 65 |
| February | 12 | | August | 65 |
| March | 15 | | September | 65 |
| April | 18 | | October | 30 |
| May | 22 | | November | 30 |
| June | 40 | | December | 20 |
(i) Highest: July, August and September, with 65 cases each.
(ii) Lowest: January, with 10 cases.
(iii) Why those months. July to September is the monsoon and immediately post-monsoon period in most of India, and every factor points the same way:
- Rain leaves still water collected in pots, tyres, coolers, drains and puddles — and Table 3.1 names avoiding areas with still water as a dengue precaution precisely because that is where mosquitoes breed
- Warmth and high humidity let mosquitoes survive longer and breed faster
- More standing water plus faster breeding means a much larger mosquito population carrying the dengue virus
Notice the shape of the curve supports this: the rise begins in June (40, up from 22) as the rains arrive, holds through the peak, and falls sharply in October (30) as they end.
(iv) Preventive steps before the peak season — the key word is before, since the aim is to act while numbers are still low:
- Remove or cover still water — empty coolers, pots, tyres and containers weekly
- Clear drains and clean surroundings so rainwater does not collect
- Distribute or promote mosquito nets and repellents
- Run awareness campaigns before the monsoon, telling people to check their homes
- Promote long-sleeved clothes, and screens on windows
- Ensure hospitals are prepared for the expected rise in cases
✦ Answer: (i) July, August and September (65 each); (ii) January (10); (iii) the monsoon leaves still water for mosquitoes to breed in, with warmth and humidity speeding breeding; (iv) before the season, remove standing water, clear drains, distribute nets and repellents, and run awareness campaigns.
84 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 44, Q8
Imagine you are in charge of a school health campaign. What key messages would you use to reduce communicable and non-communicable diseases?
Hint. The two types need different messages, because they have different causes.
Why two sets of messages. Communicable diseases spread from person to person, so the messages must be about stopping transmission. Non-communicable diseases do not spread at all, so those messages must be about how we live. A campaign that confuses the two wastes its effort.
Messages against communicable diseases:
- Wash your hands with soap and water — before eating, after using the toilet
- Cover your mouth and nose when you cough or sneeze
- Stay home when you are unwell — it helps you recover and protects everyone else
- Don't share handkerchiefs, towels, bottles or food
- Drink boiled or safe water; eat properly cooked food
- Get vaccinated — it protects you and the people around you
- No still water around the school or home — that is where mosquitoes breed
- Keep our surroundings clean
Messages against non-communicable diseases:
- Eat a balanced diet — fruits, vegetables and whole grains; limit processed, fatty and sugary food
- Play and move every day — walking, running, cycling, sport
- Sleep enough, and keep regular hours
- Limit screen time
- Say NO to tobacco, alcohol and drugs
- Look after your mind too — talk to friends and family; ask a counsellor for help if you are struggling
One message that covers both: prevention is better than cure — and a second worth adding, that health is physical, mental and social, so a campaign that only talks about the body is missing a third of the subject.
How to make it work. Short slogans, posters, a demonstration of proper hand-washing, a doctor invited to speak, a weekly check for standing water, and student-led activities so it is not simply a list of rules from adults.
✦ Answer: for communicable diseases — hand-washing, covering coughs, staying home when ill, not sharing personal items, safe water and food, vaccination and removing still water; for non-communicable — balanced diet, daily activity, enough sleep, less screen time, no tobacco or alcohol, and care for mental and social well-being.
93 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 44, Q9
It is recommended that we should not take an antibiotic for a viral infection like a cold, a cough, or flu. Give the possible reasons for this recommendation.
Hint. There are two reasons — one about it not working, one about the harm it does.
Reason 1 — it cannot work. Antibiotics target parts of bacterial cells that are different from human or other animal cells. A cold, cough or flu is caused by a virus, which is not a bacterium and does not have those structures — indeed, as Chapter 2 explained, a virus is acellular, not made of a cell at all. So there is nothing for the antibiotic to attack. The chapter states it directly: antibiotics do not work against viruses.
Reason 2 — it does active harm. Taking antibiotics when they are not required is one of the two named causes of antibiotic resistance. The mechanism:
- The antibiotic kills good bacteria that protect the body from infection
- A few bacteria develop resistance and survive
- Those resistant bacteria grow and take over, their competitors having been removed
- Some transfer resistance to other bacteria, spreading it further
So an antibiotic taken for a cold does nothing for the cold, while making future bacterial infections harder to treat, with greater risk of complications, prolonged illness and even death.
What to do instead. Rest at home, which helps the body recover and stops the infection spreading; the immune system deals with most viral infections on its own.
✦ Answer: because antibiotics only work on bacteria — they attack bacterial cell structures that a virus does not have — and because unnecessary use breeds antibiotic resistance, killing protective bacteria and letting resistant strains take over, so the drug fails when it is genuinely needed.
103 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 44, Q10
Which of the following may spread if drinking water gets contaminated by the excreta of an infected person: Hepatitis A, Tuberculosis, Poliomyelitis, Cholera, Chickenpox?
Hint. Sort them by route of transmission, not by how serious they are.
The test. The question describes contamination of drinking water by human excreta, so the answer is every disease that spreads by the water-and-food route. Sort each one by how it actually travels:
| Disease | Route of spread | Spreads this way? |
|---|
| Hepatitis A | Contaminated water and food (Table 3.1) | ✓ Yes |
| Tuberculosis | Air — from an infected person's cough (Table 3.1) | ✗ No |
| Poliomyelitis | Contaminated water and food | ✓ Yes |
| Cholera | Contaminated water and food (Table 3.1) | ✓ Yes |
| Chickenpox | Air and direct contact (Table 3.1) | ✗ No |
The two that do not fit. Tuberculosis settles in the lungs and is passed on when an infected person coughs; Table 3.1 places it firmly among the airborne diseases. Chickenpox likewise infects the respiratory tract and skin and spreads through the air and by contact — which is why its preventive measure is complete isolation of the patient, not boiled water.
The pattern in the three that do. All three are prevented by the same measures — boiled drinking water, properly cooked food, and good sanitation — which is exactly why the Odisha campaign to stop open defecation reduced diarrhoea and infections.
✦ Answer: Hepatitis A, Poliomyelitis and Cholera — all spread by the faecal contamination of water and food; tuberculosis and chickenpox do not, since both spread through the air.
114 marksCuriosity Grade 8, Chapter 3, Keep the curiosity alive, page 45, Q11
When our body encounters a pathogen for the first time the immune response is generally low, but on a second exposure to the same pathogen the response is much stronger. Why is it so?
Hint. The immune system does something on the first encounter besides fighting.
The first encounter. The pathogen is unfamiliar. The immune system has to recognise it as harmful and work out how to attack it, which takes time — so the response builds slowly and stays comparatively weak, and you fall ill while it catches up.
What is left behind. The immune system does not simply win and forget. It remembers the pathogen — this is what the chapter calls acquired immunity, protection developed after exposure to a pathogen or a vaccine.
The second encounter. Because the pathogen is now recognised immediately, the immune system attacks faster and much more strongly, often destroying it before you notice any symptoms at all. That is why many diseases — chickenpox and measles among them — are usually caught only once.
Why this is the whole basis of vaccination. A vaccine works by training the immune system to recognise and attack harmful germs using weakened, dead or harmless parts of the pathogen. It is a deliberate first exposure that is safe — so when the real pathogen arrives, your body is already meeting it for the second time and mounts the strong, fast response instead of the slow, weak one.
And why the tetanus shot works. It contains an inactivated bacterial toxin that lets the immune system develop protection without causing the disease — the same principle exactly.
✦ Answer: because on the first exposure the immune system must recognise an unfamiliar pathogen from scratch, but it remembers it afterwards — giving acquired immunity — so on a second exposure it recognises and attacks faster and far more strongly; this memory is precisely what vaccines create in advance.
Solutions written by the tuition.in editorial team and checked against NCERT Curiosity - Textbook of Science for Grade 8 (hecu103.pdf), Chapter 3 'Health: The Ultimate Treasure', pages 28-45, Reprint 2026-27. HAND-WRITTEN throughout. Page count verified against the printed contents page (hecu1ps.pdf p.18): 18 pages, 28-45, matching exactly. Covers the 5 'Probe and ponder' prompts (p.28), all 7 activities (3.1-3.7), every in-text section (3.1-3.5.1), both 'Our scientific heritage' boxes (Ayurveda; variolation and teekedaars), both 'Be a scientist' boxes (Kamal Ranadive; Maharaj Kishan Bhan), both 'Think like a scientist' boxes (Jenner; Fleming), the 'Ever heard of' box on India's vaccine production, the 11 numbered 'Keep the curiosity alive' exercises (pp.42-45) and the 5 'Discover, design, and debate' projects (p.45). ALL OF TABLE 3.1 TRANSCRIBED FROM THE PDF rather than from memory - 10 diseases with causal agent, site of infection, symptoms and preventive measures, in the book's own three groupings (air-spread: common cold and influenza, chickenpox, measles, tuberculosis; water- and food-spread: hepatitis A, cholera, typhoid, ascariasis; insect-transmitted: malaria, dengue). Exercise Q7's dengue figures were transcribed and re-read: Jan 10, Feb 12, Mar 15, Apr 18, May 22, Jun 40, Jul 65, Aug 65, Sep 65, Oct 30, Nov 30, Dec 20 - so the three peak months are July, August and September at 65 each and the lowest is January at 10, with the rise beginning in June and the fall in October, which matches the monsoon and is the basis of the answer to (iii). Exercise Q10 was answered by route of transmission using Table 3.1: hepatitis A, poliomyelitis and cholera spread by faecal contamination of water, while tuberculosis and chickenpox are airborne and do not. THREE POINTS OF DELIBERATE CAUTION. (1) The 'could climate change lead to NEW types of diseases' prompt is answered as changing WHERE, WHEN and HOW MUCH existing diseases occur, with the emergence of genuinely new diseases flagged as an open research question rather than asserted. (2) The CPR project answer gives the broad current sequence and India's emergency number 112, but states plainly that CPR is a practical skill that cannot be learnt from a written description, that guidelines are periodically revised, and that it must be learnt hands-on from a qualified instructor - which is what the book itself asks by suggesting a doctor demonstrate a mock drill. (3) The four Indian scientists in the reading project are given as starting points describing the FIELD each worked in, with the student told to verify and cite sources and to note disagreement between them, rather than being handed specific dates and claims to reproduce.. Questions are referenced from the NCERT textbook for identification.
