What is Health and Diseases in Class 8 Science NCERT?

In Class 8 Science NCERT Curiosity, Health and Diseases is the topic that explains health and how it connects to related concepts like WHO definition. This part of Chapter 3 — Health: The Ultimate Treasure covers the definitions, key examples, and everyday applications that Class 8 students need to…

What is Health and Diseases in Class 8 Science?

In Class 8 Science NCERT Curiosity, Health and Diseases is the topic that explains health and how it connects to related concepts like WHO definition. This part of Chapter 3 u2014 Health: The Ultimate Treasure covers the definitions, key examples, and everyday applications that Class 8 students need to understand. The NCERT textbook introduces Health and Diseases through activities, questions, and observations that build scientific thinking rather than rote memorisation. Mastering this topic helps learners answer both theory and competency-based questions in CBSE school exams, and it also forms the foundation for more advanced concepts in Class 9 and Class 10 Science.

Why is Health and Diseases important for Class 8 students?

Health and Diseases is important for Class 8 students because it develops the core scientific reasoning skills needed for all higher-class science learning. The NCERT Curiosity Chapter 3 presents health through real-life contexts so students see how science applies to their daily lives u2014 from food and health to weather, technology, and the environment. Understanding Health and Diseases also trains students in observation, hypothesis-making, and explanation, matching NEP 2020's competency-based learning goals. Students who grasp this topic well find it far easier to tackle related Class 9 and 10 topics, and they also perform better on CBSE competency-based and assertion-reason questions.

What are the key concepts covered in Health and Diseases?

The key concepts in Health and Diseases as per the NCERT Class 8 Science Curiosity textbook include health, WHO definition, physical health, mental health, social health. Each concept is explained with definitions, labelled diagrams, and NCERT activities that let students investigate the phenomenon themselves. The chapter also connects these concepts to everyday examples and to previous learning from Grades 6 and 7, so students build a coherent understanding rather than isolated facts. For CBSE exam preparation, students should be able to define each concept in their own words, draw a simple diagram where relevant, and give one real-life example u2014 this mirrors the three-part structure commonly used in NCERT answer keys.

How does NCERT Curiosity teach Health and Diseases?

NCERT Curiosity teaches Health and Diseases through an inquiry-based approach that starts with observations from daily life, then moves to guided activities, and finally arrives at the scientific explanation. For Chapter 3 u2014 Health: The Ultimate Treasure, the textbook uses predict-observe-explain activities so Class 8 students discover concepts like health themselves rather than being told. Diagrams, tables, and short experiments reinforce the learning, and every section ends with questions that test understanding at multiple Bloom's Taxonomy levels. This approach aligns with NEP 2020 and is designed to build scientific temper, not just factual recall u2014 making it far more effective than traditional chalk-and-talk teaching.

What real-life examples illustrate Health and Diseases?

Real-life examples of Health and Diseases that Class 8 students encounter every day include applications of health and WHO definition in the home, kitchen, environment, or body. The NCERT Curiosity textbook uses familiar Indian contexts u2014 such as foods, seasons, weather, traffic, cooking, and natural phenomena u2014 so students immediately see the relevance of the concept. When answering CBSE exam questions, students are often asked to give one or two such real-life examples, and the ability to do so crisply signals deep understanding. Practising examples from the textbook and also thinking of original examples from your own experience is one of the best ways to prepare.

How is Health and Diseases tested in CBSE Class 8 Science exams?

Health and Diseases is tested in CBSE Class 8 Science exams through a mix of MCQs, short-answer questions, long-answer questions, and competency-based questions (CBQs) that align with NEP 2020. MCQs test quick recall of terms like health, while short answers require a one or two-line definition plus example. Long-answer questions often ask students to describe a process, explain a diagram, or compare two related concepts. Competency-based questions give a scenario and ask students to apply the concept u2014 for example, identifying which idea from Health: The Ultimate Treasure explains a given everyday observation. Consistent practice across all four formats delivers the best exam outcomes.

What is Health and Diseases in Class 8 Science?

In Class 8 Science NCERT Curiosity, Health and Diseases is the topic that explains health and how it connects to related concepts like WHO definition. This part of Chapter 3 — Health: The Ultimate Treasure covers the definitions, key examples, and everyday applications that Class 8 students need to understand. The NCERT textbook introduces Health and Diseases through activities, questions, and observations that build scientific thinking rather than rote memorisation. Mastering this topic helps learners answer both theory and competency-based questions in CBSE school exams, and it also forms the foundation for more advanced concepts in Class 9 and Class 10 Science.

Why is Health and Diseases important for Class 8 students?

Health and Diseases is important for Class 8 students because it develops the core scientific reasoning skills needed for all higher-class science learning. The NCERT Curiosity Chapter 3 presents health through real-life contexts so students see how science applies to their daily lives — from food and health to weather, technology, and the environment. Understanding Health and Diseases also trains students in observation, hypothesis-making, and explanation, matching NEP 2020's competency-based learning goals. Students who grasp this topic well find it far easier to tackle related Class 9 and 10 topics, and they also perform better on CBSE competency-based and assertion-reason questions.

What are the key concepts covered in Health and Diseases?

The key concepts in Health and Diseases as per the NCERT Class 8 Science Curiosity textbook include health, WHO definition, physical health, mental health, social health. Each concept is explained with definitions, labelled diagrams, and NCERT activities that let students investigate the phenomenon themselves. The chapter also connects these concepts to everyday examples and to previous learning from Grades 6 and 7, so students build a coherent understanding rather than isolated facts. For CBSE exam preparation, students should be able to define each concept in their own words, draw a simple diagram where relevant, and give one real-life example — this mirrors the three-part structure commonly used in NCERT answer keys.

How does NCERT Curiosity teach Health and Diseases?

NCERT Curiosity teaches Health and Diseases through an inquiry-based approach that starts with observations from daily life, then moves to guided activities, and finally arrives at the scientific explanation. For Chapter 3 — Health: The Ultimate Treasure, the textbook uses predict-observe-explain activities so Class 8 students discover concepts like health themselves rather than being told. Diagrams, tables, and short experiments reinforce the learning, and every section ends with questions that test understanding at multiple Bloom's Taxonomy levels. This approach aligns with NEP 2020 and is designed to build scientific temper, not just factual recall — making it far more effective than traditional chalk-and-talk teaching.

What real-life examples illustrate Health and Diseases?

Real-life examples of Health and Diseases that Class 8 students encounter every day include applications of health and WHO definition in the home, kitchen, environment, or body. The NCERT Curiosity textbook uses familiar Indian contexts — such as foods, seasons, weather, traffic, cooking, and natural phenomena — so students immediately see the relevance of the concept. When answering CBSE exam questions, students are often asked to give one or two such real-life examples, and the ability to do so crisply signals deep understanding. Practising examples from the textbook and also thinking of original examples from your own experience is one of the best ways to prepare.

How is Health and Diseases tested in CBSE Class 8 Science exams?

Health and Diseases is tested in CBSE Class 8 Science exams through a mix of MCQs, short-answer questions, long-answer questions, and competency-based questions (CBQs) that align with NEP 2020. MCQs test quick recall of terms like health, while short answers require a one or two-line definition plus example. Long-answer questions often ask students to describe a process, explain a diagram, or compare two related concepts. Competency-based questions give a scenario and ask students to apply the concept — for example, identifying which idea from Health: The Ultimate Treasure explains a given everyday observation. Consistent practice across all four formats delivers the best exam outcomes.

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What is Health and Diseases

🎓 Class 8 Science CBSE Theory Ch 3 — Synthetic Fibres and Plastics ⏱ ~27 min

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Probe and Ponder

Before we dive into the science of staying well, sit with these questions for a moment:

When you catch a common cold, how does your body fight back? Why does it feel worse some days and better on others?
Why do we rarely hear of typhoid or polio in our neighbourhood today, when they were common a generation ago?
Can climate change create new diseases, or help old diseases spread to new places?
Why do some groups of people — children, the elderly, people living in crowded areas — get affected more than others?

By the end of this chapter, you will be able to answer every one of these questions like a real health investigator.

3.1 What is Health?

Most of us think that being healthy simply means "not being sick". But the World Health Organization (WHO) gives a much richer definition:

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

The Three Components of Health L2 Understand

💪

Physical Health

Fitness of the body — eating nourishing food, getting enough sleep, exercising, and having energy to play, learn, and work.

🧠

Mental Health

How we think and feel — managing emotions, handling stress, focusing on studies, and feeling calm and happy inside.

🤝

Social Health

Healthy relationships — loving family, supportive friends, respect in school and community, and a sense of belonging.

True health is the beautiful sum of all three: a healthy body + a healthy mind + happy relationships. If any one of them is missing, health is incomplete.

Health sits at the intersection of physical, mental, and social well-being — not just the absence of disease.

3.2 Disease — When Health is Disturbed

When the body or the mind stops working normally, we say a person has a disease. Doctors and patients give two different kinds of clues that something is wrong:

Signs vs Symptoms

Signs (objective)	Symptoms (subjective)
What others can observe about you — fever (measured by thermometer), rash, swelling, redness, yellow eyes.	What you feel but others cannot see — pain, tiredness, headache, nausea, dizziness.

Good doctors pay attention to both. A child might feel weak (symptom) and have a fever of 102°F (sign) — together they tell a clearer story.

3.3 Types of Diseases

Diseases fall into two big families depending on whether they can spread from one person to another:

A. Communicable (Infectious) Diseases L1 Remember

These diseases spread from one person to another through tiny living invaders called pathogens. Pathogens include bacteria, viruses, fungi, protozoa, and sometimes worms.

Pathogens and the diseases they cause

Pathogen	Diseases they cause
Bacteria	Tuberculosis (TB), typhoid, cholera, tetanus
Virus	Common cold, flu, COVID-19, measles, chickenpox, polio, AIDS
Fungi	Athlete's foot, ringworm
Protozoa	Malaria, amoebic dysentery

Pathogens come in many shapes and sizes. Viruses are the smallest, protozoa the largest.

How do communicable diseases spread?

💨

Air (droplets)

Cough & sneeze droplets spread cold, flu, TB, COVID-19.

💧

Water

Dirty water carries cholera, typhoid, diarrhoea.

🍲

Food

Stale or uncovered food causes food poisoning and hepatitis A.

🦟

Vectors

Mosquitoes carry malaria, dengue; flies carry typhoid.

🤝

Physical contact

Touching spreads chickenpox, scabies, ringworm.

Pathogens can travel from an infected person to a healthy one by five main routes.

B. Non-Communicable Diseases

These diseases do NOT spread between people. You cannot "catch" diabetes from your friend. Instead, they arise from inside the body due to:

Genetics — inherited from parents (thalassaemia, some cancers)
Lifestyle — poor diet, no exercise, stress, smoking (heart disease, diabetes, hypertension)
Deficiency — lack of vitamins/minerals (anaemia, scurvy, rickets)
Wear and tear — with age (arthritis, osteoporosis)

Common examples: diabetes, hypertension, cancer, heart disease, asthma, osteoporosis, arthritis. Because many of them are driven by how we live, they are often called "lifestyle diseases".

Two families of diseases — each needs a different kind of prevention and care.

🎯 Try It: Disease Classifier L3 Apply

For each disease below, click Communicable or Non-Communicable. See if you get all 8 right!

1. Cholera

2. Diabetes

3. Malaria

4. Heart disease

5. Tuberculosis

6. Asthma

7. Chickenpox

8. Osteoporosis

🔬 Activity 3.1 — Map Your Family's HealthL4 Analyse

🤔 Predict first: In your family, which is more common — communicable diseases or non-communicable diseases?

Over one week, ask each family member (gently!) about any illness they had in the past year.
Make a simple table with columns: Name, Illness, Type (C or NC), How it spread/started.
Count how many were communicable and how many were non-communicable.
Was your prediction correct? In India today, the share of non-communicable diseases is rising — see if your family's data shows this trend.

Finding: In most Indian families, non-communicable diseases (diabetes, hypertension, back pain, asthma) now outnumber communicable ones (cold, flu, stomach infection). This is called the "epidemiological transition" — and it means prevention through lifestyle has become more important than ever.

📋 Competency-Based Questions

Meera's school recently had three students absent in one week. Aisha had fever and a runny nose, Rohan had patchy itching around his foot that his doctor called "athlete's foot", and Kabir was off school because his blood sugar went too high — he has had diabetes since age 7. Meera wonders if all three illnesses belong to the same category.

Q1. L2 Understand Which of Meera's friends had a non-communicable disease?

A. Aisha
B. Rohan
C. Kabir
D. All three

Answer: C. Kabir's diabetes cannot spread to others — it is non-communicable. Aisha (cold) and Rohan (athlete's foot, a fungal infection) both have communicable diseases.

Q2. L1 Remember List the five main types of pathogens that cause communicable diseases. (Short Answer)

Answer: Bacteria, viruses, fungi, protozoa, and worms.

Q3. L3 Apply A doctor notes "Temperature 39°C, red rash on arms" and the patient says "I feel dizzy and my head hurts". Separate these four observations into signs and symptoms. (2 marks)

Signs (observed by doctor): Temperature 39°C; red rash on arms. Symptoms (felt by patient): dizziness; headache.

Q4. L4 Analyse True or False — "If a disease is caused by a pathogen, it must be communicable." Justify. (3 marks)

Mostly True. A pathogen can transmit from one host to another, making the disease communicable. However, some pathogens (like tetanus bacteria from soil) enter a single person but don't spread person-to-person. So pathogen-based diseases are generally communicable, but the exact route of transmission matters.

Q5. L6 Create HOT: Climate change is making Indian summers longer. Predict two ways this could change the pattern of communicable diseases. (3 marks)

Hint: (1) Mosquitoes breed in warmer, wetter conditions, so vector-borne diseases like dengue and malaria can spread to new regions and last for more months of the year. (2) Warmer weather can cause faster spoiling of food and water sources, increasing food- and water-borne diseases like cholera and typhoid.

🔗 Assertion–Reason Questions

Assertion (A): The WHO definition of health includes mental and social well-being, not just the absence of disease.

Reason (R): A person can be free of any illness and yet feel deeply unhappy or socially isolated.

A. Both A and R are true, and R correctly explains A.
B. Both A and R are true, but R does not explain A.
C. A is true, R is false.
D. A is false, R is true.

Answer: A. Both statements are true, and the reason correctly explains why health must include mental and social dimensions.

Assertion (A): Diabetes can spread from one family member to another through touching.

Reason (R): Diabetes is a non-communicable disease caused mainly by lifestyle factors and genetics.

A. Both A and R are true, and R correctly explains A.
B. Both A and R are true, but R does not explain A.
C. A is true, R is false.
D. A is false, R is true.

Answer: D. A is false — diabetes does not spread by contact. R is true and actually disproves A.

Assertion (A): Signs and symptoms mean the same thing.

Reason (R): Signs are what a doctor can observe, while symptoms are what the patient feels subjectively.

A. Both A and R are true, and R correctly explains A.
B. Both A and R are true, but R does not explain A.
C. A is true, R is false.
D. A is false, R is true.

Answer: D. A is false — signs and symptoms are different. R correctly explains the difference.

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