Class 8 Science – Curiosity (NCERT New Book 2026-27)
Chapter 3: Health: The Ultimate Treasure
Full A-Z Detailed Notes (Easy to Remember Style)
These notes are made super simple, short, and memorable with bullets, tables, mnemonics, key phrases, and “Remember This” boxes. Everything comes straight from the NCERT Curiosity textbook. No copying from any website – just clear, student-friendly explanation with original graphics created for you.
1. Probe & Ponder (Start with these questions – they open your mind!)
- How does your body fight a common cold?
- Why are old diseases like smallpox/polio gone, but diabetes and heart problems are rising?
- Can climate change bring new diseases?
- Can stress or worry actually make you sick?
- Why do some people/groups get hit harder during outbreaks?
Remember: Health is not just “no disease” – it is complete Physical + Mental + Social well-being (WHO definition).
2. 3.1 Health: Is It More Than Not Falling Sick?
Health = P.M.S. Formula (easy mnemonic) Physical well-being Mental well-being Social well-being
- WHO says: “Health is a state of complete physical, mental, and social well-being and not merely the absence of disease.”
- Ayurveda adds: Health = balance of body + mind + surroundings. Follow dinacharya (daily routine) and ritucharya (seasonal routine), eat fresh food as per your body type (prakriti), do yoga, meditation, stay clean, sleep well, keep calm mind.
Real-life Story (Activity 3.1): A new-school boy felt lonely → used phone a lot → headaches, weight loss, no sleep → needed friends + counsellor. Lesson: Loneliness and too much screen time harm mental health even if body looks fine.
Graphic: What is True Health?
3. 3.2 How Can We Stay Healthy?
Golden Rule: “Prevention is better than cure” starts with daily habits!
Good Habits (Do these – “5 Friends of Health”)
- Personal hygiene & cleanliness
- Balanced diet (fruits, vegetables, whole grains)
- Regular exercise/play outdoors
- Enough sleep + relaxation/yoga
- Positive attitude + time with family & friends
Bad Habits (Avoid these – “5 Enemies of Health”)
- Too much mobile/screen time
- Junk/fast food daily
- Sleeping very late
- Skipping meals (especially breakfast)
- Tobacco, alcohol, drugs
3.2.1 Healthy Lifestyle Tips (Easy 6-Step Formula)
- Eat balanced → Avoid processed/sugary/fatty food
- Stay active (walk, cycle, play)
- Limit screen time → Spend time in nature
- Sleep well
- Yoga/pranayama daily
- Say NO to tobacco, alcohol, drugs
3.2.2 Clean Environment = Healthy You Clean playground (Fig. 3.3a) vs dirty one full of flies/mosquitoes (Fig. 3.3b). Clean air & water are must! Air Quality Index (AQI) tells how polluted air is. Polluted air → cough, asthma. Community tip: Good sanitation (toilets, no open defecation) reduces diarrhoea and infections (example: Odisha campaign success).
Graphic: Healthy Habits Wheel
4. 3.3 How Do We Know We Are Unwell?
Symptom = What you feel (pain, tiredness, dizziness) Sign = What doctor sees/measures (fever, rash, high BP, swelling)
Body gives signals when something is wrong.
5. 3.4 Diseases: Causes & Types
Disease = Condition when body or mind does not work normally. Pathogens = Germs that cause disease (bacteria, virus, fungi, worms, protozoa).
Two Big Types (Easy Mnemonic: C & N)
- Communicable → Spread from person to person (by pathogens)
- Non-communicable → Do not spread (lifestyle or deficiency)
Table 3.1: Common Communicable Diseases (Learn in 3 Groups – AIR, WATER/FOOD, INSECTS)
| Group | Disease | Germ | Symptoms | Prevention (Key) |
|---|---|---|---|---|
| Air | Common cold & Flu | Virus | Nose block, cough, fever, body ache | Wash hands, mask, no sharing items |
| Chickenpox | Virus | Itchy rashes, blisters | Isolation, vaccination | |
| Measles | Virus | Fever, red rashes | Isolation, vaccination | |
| TB | Bacteria | Cough, fever, night sweats | Cover mouth, vaccination, avoid contact | |
| Water/Food | Hepatitis A | Virus | Jaundice, vomiting, tiredness | Boiled water, vaccination |
| Cholera | Bacteria | Severe diarrhoea | Clean food/water, hygiene | |
| Typhoid | Bacteria | Fever, headache, diarrhoea | Clean food/water, hygiene | |
| Ascariasis (worms) | Worms | Worms in stool, weight loss, anaemia | Clean food/water, hygiene | |
| Insects | Malaria | Protozoa | High fever, chills, sweating | Mosquito net, no stagnant water |
| Dengue | Virus | Fever, joint pain (“break-bone fever”) | Mosquito net, no stagnant water |
Remember Trick: AIR diseases → cover mouth & mask; WATER → boil & cook; INSECT → net & no water logging.
Non-Communicable Diseases (Table 3.2 style) Caused by poor diet, no exercise, stress, pollution, genetics. Examples: Obesity, Diabetes, High BP, Heart disease, Cancer, Asthma, Deficiency diseases (Anaemia, Scurvy, Goitre). India fact: Most deaths now from these NCDs because of junk food + less activity.
Graphic: Communicable vs Non-Communicable
6. 3.5 How to Prevent & Control Diseases?
Key Mantra: Prevention > Cure
Immunity = Body’s natural army that fights germs. Vaccination = Training the army (acquired immunity). Vaccine is weakened/dead germ or its part → body learns to fight without getting sick. Examples: Polio drops, Measles, Tetanus shot, Hepatitis, COVID vaccine. India is a big vaccine producer!
History in short: Edward Jenner discovered first vaccine using cowpox to fight smallpox (now eradicated worldwide). Ancient India used variolation too.
Community Health = Everyone together keeps surroundings clean (toilets, no garbage, clean water). Example: Odisha sanitation campaign reduced diarrhoea.
Final Prevention Tips (Easy 7-Point List)
- Personal & community hygiene
- Balanced diet + exercise
- Vaccination on time
- Safe drinking water & cooked food
- Mosquito control
- Say no to tobacco/alcohol
- Manage stress & sleep well
Be a Scientist: Dr. Kamal Ranadive showed how diet, tobacco, pollution increase cancer risk – healthy lifestyle matters!
Graphic: How Vaccine Works (Simple Flow)
Quick Revision Box (A-Z Memory Tips)
- Health = P.M.S. (not just no disease)
- Stay healthy = 5 Friends (diet, exercise, sleep, clean, friends)
- Diseases = C (spread) vs N (no spread)
- Communicable = 3 routes → AIR (mask), WATER/FOOD (boil), INSECT (net)
- Immunity = Body’s army; Vaccine = training
- Prevention = Best medicine
Activity Tip for Exam: Make your own Table 3.1 and 3.2 in notebook – it helps score full marks!
These notes cover every single point from the chapter in easy language. Revise once daily – you will remember everything for exams! Stay healthy and curious! 🌟