📘 Class 8 – Science

Q. What is crop production?

Ans: Crop production is growing plants for food.

Q. What is agriculture?

Ans: Agriculture is the practice of farming.

Q. Name two Kharif crops.

Ans: Rice and maize are Kharif crops.

Q. Name two Rabi crops.

Ans: Wheat and gram are Rabi crops.

Q. What is ploughing?

Ans: Ploughing loosens the soil.

Q. Why is soil loosened?

Ans: It helps roots grow and breathe.

Q. What is sowing?

Ans: Sowing is planting seeds in soil.

Q. What is manure?

Ans: Manure improves soil fertility.

Q. What are fertilizers?

Ans: Fertilizers supply nutrients to crops.

Q. Why is irrigation needed?

Ans: Irrigation supplies water to crops.

Q. What is agriculture?

Ans: Agriculture is the practice of growing crops and rearing animals.

Q. What is crop production?

Ans: Crop production is the process of growing plants on a large scale for food.

Q. Name two main types of crops in India.

Ans: Kharif crops and Rabi crops.

Q. What are Kharif crops?

Ans: Crops grown in the rainy season are called Kharif crops.

Q. Give two examples of Kharif crops.

Ans: Rice and maize are Kharif crops.

Q. What are Rabi crops?

Ans: Crops grown in winter season are called Rabi crops.

Q. Give two examples of Rabi crops.

Ans: Wheat and gram are Rabi crops.

Q. What is preparation of soil?

Ans: Preparation of soil means loosening and turning the soil.

Q. Why is ploughing important?

Ans: Ploughing helps roots grow deep and improves soil aeration.

Q. What is plough?

Ans: Plough is a tool used for loosening the soil.

Q. What is sowing?

Ans: Sowing is the process of planting seeds in the soil.

Q. Why should healthy seeds be selected?

Ans: Healthy seeds grow into healthy plants.

Q. What is seed drill?

Ans: Seed drill is a tool used for sowing seeds at equal depth.

Q. What is manure?

Ans: Manure is organic matter added to soil to increase fertility.

Q. Why is manure useful?

Ans: Manure improves soil structure and water holding capacity.

Q. What are fertilizers?

Ans: Fertilizers are chemical substances that supply nutrients to crops.

Q. Give one disadvantage of fertilizers.

Ans: They can reduce soil fertility over time.

Q. What is irrigation?

Ans: Irrigation is the supply of water to crops at regular intervals.

Q. Why is irrigation important?

Ans: Water is needed for growth and nutrient absorption.

Q. Name one traditional irrigation method.

Ans: Moat is a traditional irrigation method.

Q. Name one modern irrigation method.

Ans: Sprinkler system is a modern method.

Q. What is weeding?

Ans: Weeding is removal of unwanted plants from fields.

Q. Why should weeds be removed?

Ans: They compete with crops for nutrients and water.

Q. Name one weeding tool.

Ans: Hoe is used for weeding.

Q. What are pesticides?

Ans: Pesticides protect crops from pests.

Q. What is harvesting?

Ans: Harvesting is cutting of mature crops.

Q. What is threshing?

Ans: Threshing separates grains from harvested crops.

Q. What is winnowing?

Ans: Winnowing separates grains from chaff.

Q. What is storage of grains?

Ans: Keeping grains safe for future use.

Q. Why proper storage is needed?

Ans: To protect grains from pests and moisture.

Q. Speed of light in vacuum?

Ans: 3 × 10^8 m/s

Q. Unit of force?

Ans: Newton (N)

Q. What is Newton’s First Law?

Ans: A body remains at rest or in uniform motion unless acted upon by an external force.

Q. What is Ohm’s law?

Ans: V = IR, where I is current and R is resistance.

Q. Unit of electric current?

Ans: Ampere (A)

Q. Formula for work done?

Ans: W = F × d

Q. Frequency of standard AC in India?

Ans: 50 Hz

Q. Define density.

Ans: Mass per unit volume (ρ = m/V)

Q. Acceleration due to gravity on Earth?

Ans: 9.8 m/s²

Q. Principle of a lever?

Ans: Law of moments: F1×L1 = F2×L2

Q. Atomic number of Carbon?

Ans: 6

Q. Chemical formula of water?

Ans: H₂O

Q. What is an acid?

Ans: Substance that donates H⁺ ions in solution.

Q. What is a base?

Ans: Substance that donates OH⁻ ions in solution.

Q. pH of neutral water?

Ans: 7

Q. Formula of table salt?

Ans: NaCl

Q. Law of conservation of mass?

Ans: Mass can neither be created nor destroyed in a chemical reaction.

Q. Molar mass of CO₂?

Ans: 44 g/mol

Q. What is electrolysis?

Ans: Breaking of a compound using electricity.

Q. Symbol of Sodium?

Ans: Na

Q. Basic unit of life?

Ans: Cell

Q. Powerhouse of the cell?

Ans: Mitochondria

Q. What is photosynthesis?

Ans: Process by which plants make food using sunlight.

Q. Largest organ in the human body?

Ans: Skin

Q. What is DNA?

Ans: Deoxyribonucleic acid; carries genetic information.

Q. Blood group system discovered by?

Ans: Karl Landsteiner

Q. Function of red blood cells?

Ans: Carrying oxygen

Q. Functional unit of kidney?

Ans: Nephron

Q. What is a vaccine?

Ans: A substance used to stimulate immunity against disease.

Q. Hormone that regulates blood sugar?

Ans: Insulin

Q. Ozone layer protects us from?

Ans: Harmful UV rays

Q. Greenhouse gas responsible for global warming?

Ans: Carbon dioxide (CO₂)

Q. Renewable sources of energy?

Ans: Solar, Wind, Hydro

Q. Common fossil fuels?

Ans: Coal, Oil, Natural Gas

Q. Unit of electric power?

Ans: Watt

Q. What does pH scale measure?

Ans: Acidity or alkalinity

Q. Water cycle includes?

Ans: Evaporation, Condensation, Precipitation

Q. Function of roots?

Ans: Absorb water and minerals

Q. Function of leaves?

Ans: Photosynthesis

Q. Main component of natural gas?

Ans: Methane