Curriculum
GRADE VIII SCIENCE
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Investigative Science
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Invisible Living World
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Health
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Electricity
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Exploring Forces
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Pressure Cyclones
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Pariculate Matter
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Elements-Compounds-Mixtures
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Solutes-Solvents-Solutions
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Light-Mirrors-Lenses
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Keeping-Time-Skies
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Nature Harmony
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Our-Home-Earth
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Health
School Revise · Grade 8 · Science · Chapter 3 · Curiosity
Health: The Ultimate Treasure
Science, Class 8, Curiosity. Health is more than not being ill. This chapter explains what real health means, the difference between diseases that spread and those that do not, and how the body and good habits keep us well.
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What this chapter is about
A person with no fever can still be unwell if they are stressed, lonely or exhausted. In this chapter we learn the full meaning of health, how diseases arise or spread, and how immunity, vaccination and clean habits protect us.
1. What health really means
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Health the World Health Organisation defines health as complete physical, mental and social well-being, not merely the absence of disease; health and happiness support each other A healthy lifestyle supports all three sides: nutritious food, exercise, enough sleep, cleanliness and good company, while stress, too much screen time or loneliness can harm well-being. A disease is anything that upsets the normal working of the body or mind. In real life: The Indian scientist Dr Kamal Ranadive studied links between health and disease, showing how science protects community health. |
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Worked example 1 Question. A student has no illness but is stressed and sleeps badly. Are they fully healthy?
Answer: No. Freedom from disease is not enough; stress and poor sleep reduce mental well-being. |
2. Diseases and the body’s defence
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Communicable and non-communicable disease communicable (infectious) diseases spread through pathogens such as bacteria, viruses, fungi and worms; non-communicable diseases do not spread and come from lifestyle or the environment A symptom is what we feel, like pain or tiredness, while a sign is what can be seen or measured, like fever. The immune system fights pathogens, and a vaccine trains it using dead, weakened or harmless parts of a germ. In real life: Vaccines have almost wiped out smallpox and polio, by teaching the body’s immunity to recognise the germ in advance. |
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Worked example 2 Question. Classify typhoid and diabetes.
Answer: Typhoid is communicable (bacteria); diabetes is non-communicable (lifestyle). |
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Worked example 3 Question. How does a vaccine protect us?
Answer: A vaccine trains the immune system in advance so it can quickly fight the real germ. |
Explore with the interactive
Explore it: build a healthy lifestyle and sort diseases into communicable and non-communicable to see how the body is protected. The interactive opens right here in the lesson.
Practice set A, multiple choice
1. According to the WHO, health is …
Complete physical, mental and social well-being, not merely the absence of disease.
2. A disease that spreads through pathogens is …
Communicable (infectious).
3. The difference between a symptom and a sign is …
A symptom is what we feel (pain, tiredness); a sign is what can be seen or measured (fever, rash).
4. A vaccine is made from …
Dead, weakened or harmless parts of a germ, used to train the immune system.
Practice set B, short answer
1. Name four kinds of pathogens.
Bacteria, viruses, fungi and worms.
2. Give two habits of a healthy lifestyle.
Any two of: eat nutritious food, exercise, sleep enough, keep clean, limit screen time, keep good company.
3. Give one non-communicable disease and its cause.
Diabetes or heart disease, caused by lifestyle and environmental factors rather than germs.
Quick summary
| Idea | The idea |
| Health | physical, mental and social well-being. |
| Disease | upsets body or mind. |
| Symptom vs sign | felt vs measured. |
| Communicable | spreads by pathogens. |
| Non-communicable | lifestyle, does not spread. |
| Vaccine | trains immunity in advance. |
| Open the Virtual Lab |
These free Grade 8 Science revision notes explain what health means, the types of disease, immunity and vaccination, with clear step by step explanations and detailed labelled diagrams for every student following the new NCERT Curiosity book.
© 2026 School Revise. All rights reserved. This lesson is original content written by School Revise, aligned to the CBSE and NCERT Class 8 Science (Curiosity) syllabus. Unauthorised copying, reproduction or redistribution is not permitted. Curriculum names are used only to indicate alignment.
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