NCERT Solutions Class 8 Science - All 18 Chapters

All 18 Chapters

Crop Production and Management

Irrigation, Tools, Fertilizers

› 2

Microorganisms

Useful and harmful microorganisms

› 3

Synthetic Fibres and Plastics

Types, Properties, Environment impact

› 4

Materials: Metals and Non-Metals

Properties, Reactions

› 5

Coal and Petroleum

Fossil fuels, Products

› 6

Combustion and Flame

Types of combustion, Fire

› 7

Conservation of Plants and Animals

Biodiversity, Deforestation

› 8

Cell: Structure and Functions

Cell organelles, Division

› 9

Reproduction in Animals

Sexual and asexual reproduction

› 10

Reaching the Age of Adolescence

Puberty, Hormones

› 11

Force and Pressure

Types of forces, Pressure

› 12

Friction

Types, Factors, Advantages

› 13

Sound

Production, Transmission, Noise

› 14

Chemical Effects of Electric Current

Electrolysis, Conductors

› 15

Some Natural Phenomena

Lightning, Earthquakes

› 16

Light

Reflection, Refraction, Dispersion

› 17

Stars and the Solar System

Planets, Constellations, Moon

› 18

Pollution of Air and Water

Air pollution, Water purification

›

Chapter 1: Crop Production and Management

Q1. What are the steps involved in crop production?

Solution

Preparation of soil, Sowing, Adding manure/fertilizers, Irrigation, Protecting from weeds/pests, Harvesting, Storage.

Q2. What is the difference between manure and fertilizer?

Solution

Manure: Natural, organic, improves soil structure
Fertilizer: Chemical, concentrated nutrients, can cause pollution

Chapter 4: Materials: Metals and Non-Metals

Q1. Give two examples of metals that are soft and two that are hard.

Solution

Soft: Sodium, Potassium
Hard: Iron, Diamond (non-metal but very hard)

Q2. What happens when iron nails are placed in copper sulphate solution?

Solution

Fe + CuSO₄ → FeSO₄ + Cu
Iron displaces copper because it is more reactive.

Chapter 6: Combustion and Flame

Q1. What are the conditions necessary for combustion?

Solution

1. Combustible material (fuel)
2. Oxygen/air
3. Temperature above ignition temperature

Q2. What is the difference between complete and incomplete combustion?

Solution

Complete: Gives CO₂ and H₂O, more heat
Incomplete: Gives CO and soot, less heat, harmful

Chapter 8: Cell: Structure and Functions

Q1. What is the function of mitochondria?

Solution

Mitochondria produce energy (ATP) through cellular respiration. They are called the powerhouses of the cell.

Q2. What is the difference between plant and animal cells?

Solution

Plant cell: Cell wall, chloroplasts, large vacuole
Animal cell: No cell wall, no chloroplasts, small vacuoles, centrioles

Chapter 11: Force and Pressure

Q1. What is the difference between mass and weight?

Solution

Mass: Amount of matter, constant (kg)
Weight: Force due to gravity, varies (N), W = mg

Q2. A force of 10 N acts on an area of 2 cm². Find the pressure.

Solution

P = F/A = 10/(2 × 10⁻⁴) = 50000 Pa = 50 kPa

Chapter 14: Chemical Effects of Electric Current

Q1. What is electrolysis?

Solution

Electrolysis is the chemical effect of electric current where decomposition of an electrolyte occurs when current is passed through it.

Q2. What is the condition for a liquid to conduct electricity?

Solution

The liquid must contain dissolved ions (electrolyte) to conduct electricity. Pure water does not conduct electricity.

Chapter 16: Light

Key Laws:
• Angle of incidence = Angle of reflection
• Incident ray, reflected ray, and normal lie in same plane
• 1/v + 1/u = 1/f (mirror formula)

Q1. A ray of light strikes a plane mirror at 30° to the normal. Find the angle of reflection.

Solution

Angle of reflection = Angle of incidence = 30°

Q2. What is the lens formula?

Solution

1/f = 1/v - 1/u

Chapter 18: Pollution of Air and Water

Q1. What is smog? How is it formed?

Solution

Smog is a mixture of smoke and fog. It forms when smoke particles combine with water vapor in the air, usually during cold weather conditions.

Q2. What are the methods of water purification?

Solution

1. Boiling
2. Chlorination
3. Filtration
4. Distillation
5. UV treatment