Class 8 Science Chapter 3 – Health: The Ultimate Treasure from NCERT Curiosity with easy Notes and complete Book Solutions. Get simple explanations, important concepts, questions and answers, and revision material for effective learning, practice and exam preparation.

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Health: The Ultimate Treasure

Class 8 Science – Curiosity

Short Notes, Easy Concepts and Complete Book Questions with Answers

Chapter at a Glance

Health
Physical + Mental + Social well-being

Diseases
Communicable + Non-communicable

Prevention
Healthy habits + Hygiene + Immunity

3.1 Health: Is It More Than Not Falling Sick?

Health does not mean only being free from disease. A healthy person should have good physical, mental and social well-being.

WHO definition of health: Health is a state of complete physical, mental, and social well-being, and not merely the absence of disease.

Three Important Aspects of Health

Physical health: Our body works properly and we remain physically active.
Mental health: We can manage emotions, stress and difficult situations.
Social health: We maintain healthy relationships with family, friends and society.

Easy Concept: A person may not have a disease but may still feel lonely, stressed or unhappy. Therefore, complete health includes the body, mind and relationships.

Ayurveda and Health

Ayurveda teaches that good health is a balance of body, mind and surroundings.

Dinacharya: Daily routine.
Ritucharya: Seasonal routine.
Fresh and wholesome food according to one’s body constitution supports health.
Exercise, cleanliness, proper sleep, yoga, meditation and mindfulness help maintain well-being.

3.2 How Can We Stay Healthy?

We can stay healthy by developing good habits.

Eat nutritious and balanced food.
Maintain personal hygiene.
Keep our surroundings clean.
Exercise regularly.
Get enough sleep.
Spend time with family and friends.
Maintain a positive attitude.
Manage stress.

3.2.1 Maintain a Healthy Lifestyle

Eat plenty of fruits, vegetables and whole grains.
Avoid too much processed, fatty and sugary food.
Stay physically active.
Limit screen time.
Spend time in nature.
Get enough sleep.
Practise yoga or simple breathing exercises.
Say no to tobacco, alcohol and addictive drugs.

Remember: Healthy food + Exercise + Sleep + Hygiene + Positive mind = Better health

3.2.2 Keep the Environment Clean

A clean environment helps us stay healthy. Dirty surroundings may encourage the growth and spread of disease-causing organisms.

Keep homes and surroundings clean.
Use clean drinking water.
Dispose of waste properly.
Reduce pollution.
Prevent mosquito breeding.

Air pollution from vehicles and factories can cause problems such as coughing and asthma.

AQI: Air Quality Index tells us about the quality of air.

Our emotions and relationships also affect health. Talking with family and friends, laughing and spending time together can support mental well-being.

3.3 How Do We Know That We Are Unwell?

Symptom
What we feel

Sign
What can be seen or measured

Disease
Condition affecting normal body or mind functions

Symptom: Something that a person feels, such as pain or tiredness.

Sign: Something that can be seen or measured, such as fever, rash, high blood pressure or swelling.

Doctors use signs and symptoms to understand what may be making a person unwell.

3.4 Diseases: What Are the Causes and Types?

A disease is a condition that affects the normal working of the body or mind.

Some diseases are caused by disease-causing organisms called pathogens.

Major Types of Diseases

Communicable Diseases	Non-communicable Diseases
Caused by pathogens.	Not caused by pathogens.
Can spread from one person to another.	Do not spread from one person to another.
Examples: flu, typhoid, dengue, chickenpox.	Examples: diabetes, cancer, asthma.

Important: Changes in lifestyle such as unhealthy food, less physical activity and longer life expectancy have contributed to the increase of non-communicable diseases.

3.4.1 How are Communicable Diseases Caused and Spread?

Communicable diseases are caused by pathogens. Pathogens may enter the body through air, contaminated food or water, direct contact and other routes.

Infected person → Pathogen → Mode of transmission → Healthy person

Common Modes of Transmission

By air
By direct contact
By indirect contact
By contaminated food and water
Through insects such as mosquitoes and houseflies
Through infected animals in some diseases

Vector: An insect or other organism that spreads a pathogen from one host to another. Mosquitoes and houseflies can act as vectors.

Common Communicable Diseases

Disease	Causal Agent	Main Spread	Some Symptoms
Common cold and influenza	Virus	Air	Nasal congestion, sore throat, fever, cough, body ache
Chickenpox	Virus	Air	Fever, itchy skin, rashes, blisters
Measles	Virus	Air	Fever, sore throat, reddish rashes
Tuberculosis (TB)	Bacteria	Air	Cough, fever, fatigue, loss of appetite, night sweats
Hepatitis A	Virus	Food and water	Fatigue, fever, nausea, vomiting, jaundice
Cholera	Bacteria	Food and water	Diarrhoea and dehydration
Typhoid	Bacteria	Food and water	Headache, abdominal discomfort, fever, diarrhoea
Ascariasis	Worms	Contaminated food, water or soil	Loss of appetite, poor growth, diarrhoea, weight loss
Malaria	Protozoa	Mosquito	High fever, sweating, periodic chills
Dengue fever	Virus	Mosquito	Fever, headache, muscle and joint pain, nausea

Simple Precautions Against Infectious Diseases

Wash hands regularly with soap and water.
Cover the mouth and nose while coughing or sneezing.
Avoid sharing personal items.
Keep food and water clean.
Keep surroundings clean.
Use mosquito nets and repellents.
Stay at home and rest when unwell.
Follow appropriate vaccination advice.

3.4.2 How are Non-communicable Diseases Caused?

Non-communicable diseases may be related to lifestyle, diet and environment.

Examples include:

Diabetes
Heart disease
Cancer
Asthma
Obesity
High blood pressure

Deficiency diseases occur due to a lack of specific nutrients. Examples include scurvy, anaemia and goitre. They are non-communicable diseases.

Chronic diseases may continue for a long time and often require regular care.

3.5 How to Prevent and Control Diseases?

The simple idea is: Prevention is better than cure.

Maintain personal hygiene.
Eat a balanced diet.
Exercise regularly.
Keep the environment clean.
Get adequate sleep.
Manage stress.
Follow vaccination advice.
Avoid harmful substances.
Seek medical advice when needed.

Immunity

Immunity is the natural ability of our body to fight diseases.

The immune system protects the body from harmful pathogens.

Vaccines

Vaccines train the immune system to recognise and fight specific harmful germs. They can provide acquired immunity.

Vaccines may contain weakened or dead pathogens, harmless parts of pathogens, or other forms that safely stimulate the immune system.

Important: Vaccines are preventive. They help protect against diseases but are not medicines used to cure an illness that has already developed.

Edward Jenner and Smallpox Vaccine

Edward Jenner observed that people who had cowpox did not get smallpox. He tested the idea and this work led to the development of the first vaccine.

Observation → Hypothesis → Experiment → Result → Application

Mass vaccination eventually helped eradicate smallpox worldwide.

India’s Role in Vaccine Production

India is one of the world’s largest vaccine producers and supplies vaccines to many countries.

3.5.1 Treatment of Diseases

When the immune system cannot control an infectious disease, medical treatment may be needed.

Antibiotics are medicines used against bacterial infections. They do not work against viruses.

Penicillin

Alexander Fleming discovered penicillin in 1928. He noticed that mould on a petri dish stopped bacteria from growing.

Antibiotic Resistance

Antibiotic resistance happens when bacteria that were earlier killed by an antibiotic survive and multiply despite treatment.

How to reduce antibiotic resistance:

Use antibiotics only when prescribed by a doctor.
Take the correct dose.
Follow the prescribed duration.
Do not use antibiotics unnecessarily.

Traditional Medicine

Traditional systems such as Ayurveda, Siddha and Unani have been used in India for many years. They use natural substances and focus on healthy living. They may help with some conditions but are not suitable for every disease or every stage of illness.

Quick Revision – Important Concepts

Health
Physical, mental and social well-being

Pathogen
Disease-causing organism

Immunity
Ability to fight diseases

Vaccine
Trains immune system for protection

Symptom
What a person feels

Sign
What can be seen or measured

Probe and Ponder

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

Answer: The immune system recognises the infection and works to fight the harmful virus. Symptoms such as cough, cold and fever may appear while the body fights the infection.

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

Answer: Vaccination has greatly reduced diseases such as smallpox and polio. Diabetes and heart problems are often linked to lifestyle, diet, less physical activity and other factors.

Could climate change lead to new types of diseases?

Answer: Climate change can change temperature, rainfall and habitats. This may affect pathogens and disease-carrying insects and can change the spread of some diseases.

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

Answer: Long-term stress or worry can affect sleep, mood and body functions. It can also make it harder for us to maintain healthy habits.

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

Answer: People may differ in age, immunity, health conditions, living conditions, exposure and access to healthcare. These factors can affect their risk.

Share your questions

Answer: Students can share their own questions about health, diseases, prevention, immunity and treatment.

Activity 3.1: Let us read – Think and Reflect

Think and Reflect: What was the cause of the boy’s health problems? How did his habits and surroundings affect his well-being?

Answer: He felt lonely after moving to a new school and had little social support. Too much screen time and lack of sleep made his physical and mental well-being worse.

Activity 3.2: Let us list

List some good habits that your parents, teachers, or elders often encourage you to follow. How many of these are already a part of your daily routine? Which ones would you like to start following? Add to the list below:

Answer: Examples include keeping clean, eating balanced food, exercising, getting enough sleep, drinking clean water, limiting screen time and relaxing regularly.

Now, think about habits that are not good for your health. Add more to the list below:

Answer: Examples include too much screen time, eating junk food regularly, sleeping late, skipping meals, avoiding exercise and not maintaining hygiene.

Activity 3.3: Let us compare

Look at Fig. 3.3a and Fig. 3.3b. Which playground would you like to play in, and why?

Answer: I would like to play in Fig. 3.3a because it is clean, well-maintained and safer for health.

Have you ever found it hard to breathe in a place with a lot of smoke or dust?

Answer: Yes. Smoke and dust can irritate the respiratory system and make breathing difficult.

Activity 3.4: Let us find out

Check the information listed by referring to books, trusted websites, or asking your science teacher. Add any missing details.

Answer: The table can be checked using reliable health sources or a science teacher. Important details include the causal agent, mode of spread, symptoms and preventive measures.

Study the table and think about what simple steps can help prevent each disease.

Answer: Good hygiene, clean food and water, vaccination where available, avoiding infected people when necessary, and controlling mosquitoes can help prevent diseases.

Activity 3.5: Let us survey

Find out the three most common lifestyle-related diseases in your neighbourhood

Answer: Students should conduct a local survey. Examples may include obesity, diabetes and high blood pressure.

Talk to a doctor, nurse, health worker or even a family member who knows about health and what kind of lifestyle changes can help prevent or manage these diseases.

Answer: Ask about healthy food, regular physical activity, proper sleep, stress management and regular health check-ups.

You can also consult trusted health websites, books, teachers and doctors.

Answer: Reliable sources can provide correct information about diseases, symptoms, prevention and healthy lifestyle changes.

Activity 3.6: Let us read

What do you infer from this case study? Simple steps like good sanitation can greatly reduce the spread of communicable diseases. Find about such community campaigns held in your location. Share in your class and discuss with your peers about the impact of such initiatives.

Answer: Good sanitation reduces contamination and helps prevent infections. Community cleanliness campaigns can therefore improve public health.

Activity 3.7: Let us infer

Study the infographic given in Fig. 3.5b. How do you think the antibiotic resistance has been developed in bacterial pathogens? What precautions may be taken to reduce antibiotic resistance?

Answer: Unnecessary or incorrect use of antibiotics can allow resistant bacteria to survive and multiply. Antibiotics should be used only when prescribed, in the correct dose and for the prescribed duration.

Snapshots – Book Questions

Question 1

Group the diseases shown in the images as communicable or non-communicable.

Cold and flu Typhoid Diabetes Asthma Chickenpox

Answer:
Communicable: Cold and flu, Typhoid, Chickenpox.
Non-communicable: Diabetes, Asthma.

Question 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 diseases.

Question 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) Encourage sick students to stay home, improve hygiene, ensure good ventilation, encourage covering coughs and sneezes, and follow appropriate health advice.

(ii) Speak kindly, avoid making fun of the classmate and suggest that they inform a teacher or parent and get proper care.

(iii) Wash hands, avoid touching the face, cover coughs and sneezes, avoid sharing personal items and follow school health precautions.

Question 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) Use mosquito nets or repellents, wear long-sleeved clothes, avoid mosquito breeding areas and follow local health advice.

(ii) Mosquito nets and repellents reduce mosquito bites and therefore reduce the chance of infection.

(iii) Travellers may have a greater chance of getting infected and spreading disease.

Question 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) I would politely explain that smoking harms health and encourage him to seek support to quit.

(ii) I would politely refuse and explain that I do not want to harm my health.

(iii) Schools can provide health education, counselling, awareness programmes and supportive activities.

Question 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:
1. Do antibiotics work against viruses?
2. Can antibiotics cure diseases such as flu and common cold?
3. Why should antibiotics be taken only when prescribed by a doctor?
4. What is antibiotic resistance?

Question 7

The following table contains information about the number of dengue cases reported in a hospital over a period of one year:

S. No. 1 2 3 4 5 6
Month January February March April May June
No. of dengue cases
10 12 15 18 22 40

S. No. 7 8 9 10 11 12
Month July August September October November December
No. of dengue cases
65 65 65 30 30 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:
(i) July, August and September had the highest number of cases, with 65 cases each.

(ii) January had the lowest number of cases, with 10 cases.

(iii) Rainfall, stagnant water, warm weather and increased mosquito breeding may contribute to the increase.

(iv) Remove stagnant water, control mosquito breeding, clean drains, use mosquito-control measures and spread awareness before the peak season.

Question 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:

Wash hands regularly.
Drink safe water and eat clean, balanced food.
Maintain personal and environmental hygiene.
Follow vaccination advice.
Exercise regularly.
Get enough sleep.
Limit junk food and screen time.
Avoid tobacco, alcohol and addictive substances.
Seek medical help when needed.

Question 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 work against bacteria, not viruses. Unnecessary use can also increase antibiotic resistance.

Question 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.

Question 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: During the first exposure, the immune system learns to recognise the pathogen. It forms memory cells. When the same pathogen enters again, these memory cells help the body produce a faster and stronger immune response.

Prepare some questions based on your learnings so far …

Why?

When?

How long?

Where? Why not?

Answer: Students should frame their own questions using these question starters. For example:

Why do vaccines help prevent some diseases?
When should we wash our hands?
How long should we sleep each night?
Where can pathogens spread easily?
Why not take antibiotics without a doctor’s advice?

Discover, Design, and Debate

Health Diary: Maintain a health diary for at least a month. Record food, hygiene, exercise, sleep, screen time and emotional state.

Indian Scientists: Read about Indian scientists such as Suniti Solomon, Asima Chatterjee, Yellapragada Subbarao and Mary Poonen Lukose and learn about their contributions to health and diseases.

Smallpox: Discover how smallpox was eradicated through vaccination and why vaccination worked.

CPR: Learn the correct sequence of CPR from a qualified professional and observe a demonstration or mock drill at school.

Health and Nutrition: Interact with a doctor about malnutrition, under-nutrition and over-nutrition.

Health Card: Design a health card and decide what important health information it should contain.

Debate: Have a debate on ‘Are there ill-effects of fast food on companion animals?

Quick Revision Sheet

Term	Easy Meaning
Health	Complete physical, mental and social well-being
Disease	A condition that affects normal body or mind functions
Pathogen	Disease-causing organism
Communicable disease	Disease that can spread from one person to another
Non-communicable disease	Disease that does not spread from one person to another
Symptom	Something a person feels
Sign	Something that can be observed or measured
Immunity	Ability of the body to fight disease
Vaccine	Helps train the immune system to prevent certain diseases
Antibiotic	Medicine used against bacterial infections
Vector	Organism such as a mosquito that can spread pathogens
Chronic disease	Disease that may continue for a long time

One-Minute Revision

1. Health is more than simply not being sick.

2. Good health includes physical, mental and social well-being.

3. Communicable diseases can spread from one person to another.

4. Non-communicable diseases do not spread from person to person.

5. Pathogens cause many infectious diseases.

6. Immunity helps our body fight diseases.

7. Vaccines help prevent many serious diseases.

8. Antibiotics work against bacteria, not viruses.

9. Unnecessary antibiotic use can cause antibiotic resistance.

10. Healthy food, exercise, hygiene, sleep and a clean environment help us stay healthy.

Prepare with this NCERT Curiosity worksheet for Chapter 3. The worksheet includes important questions and revision exercises to help students understand key concepts, practise what they have learned, and prepare effectively for class tests and exams.

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Class 8 Science Chapter 3 – Health: The Ultimate Treasure | NCERT Curiosity Notes & Book Solutions