CBSE Class 8 Science Important Questions and Answers

Infinity Learn offers a valuable resource for CBSE Class 8 Science important questions and answers, designed to help students build a strong understanding of every chapter in the latest CBSE syllabus. These questions are carefully prepared to clarify key scientific concepts, boost exam preparation, and enhance student confidence and performance.

The CBSE Class 8 Science syllabus covers a wide range of essential topics such as Crop Production and Management, Microorganisms: Friend and Foe, Reproduction in Animals, Sound, and Chemical Effects of Electric Current. This comprehensive syllabus ensures that students gain deep knowledge of scientific principles and develop strong analytical skills.

CBSE Class 8 Science Chapter-wise Important Questions (Latest)

Prepare for your exams with the most updated CBSE Class 8 Science Chapter-wise Important Questions and Answers. These questions are carefully curated to cover all 13 chapters as per the latest CBSE syllabus, helping students revise essential topics efficiently and strengthen their conceptual understanding.

Why Practice Chapter-wise Important Questions?

• Focused revision of each chapter for thorough exam preparation
• Covers all key topics and concepts as per the NCERT curriculum
• Enhances problem-solving skills and scientific reasoning
• Ideal for last-minute revision and self-assessment

For comprehensive preparation, refer to the NCERT Solutions for Class 8 Science alongside these important questions. NCERT solutions provide step-by-step explanations, making it easier to understand complex topics and clarify doubts.

Chapter-wise Important Questions for Class 8 Science

CBSE Class 8 Science: 20 Important Questions - Step-by-Step Solutions

Section A: Very Short Answer Questions (1 Mark Each)

Question 1: Name two Kharif crops.

Solution:

Step 1: Recall that Kharif crops are grown during the rainy season (June-October).

Step 2: List two examples of Kharif crops:

Answer: Rice and Maize (or Cotton, Sugarcane, Jowar)

Question 2: Define fossil fuel.

Solution:

Step 1: Understand what fossil fuels are made from.

Step 2: Consider the time period of their formation.

Answer: Fossil fuels are natural fuels formed from the remains of dead plants and animals buried deep under the earth millions of years ago.

Question 3: What is the main function of platelets in blood?

Solution:

Step 1: Identify the primary role of platelets in the circulatory system.

Step 2: Focus on their response to injury.

Answer: The main function of platelets is blood clotting (coagulation) to stop bleeding when there is an injury.

Question 4: Name a metal which can be cut by a knife.

Solution:

Step 1: Think of metals that are soft and have low hardness.

Step 2: Consider alkali metals which are known for their softness.

Answer: Sodium (or Potassium, Lithium)

Question 5: What is flora?

Solution:

Step 1: Define flora in the context of biodiversity.

Step 2: Relate it to a specific region or area.

Answer: Flora refers to all the plant life found in a particular region or area.

Section B: Short Answer Questions (2 Marks Each)

Question 1: Define endangered animal with two examples.

Solution:

Step 1: Definition: Endangered animals are those species that are at risk of becoming extinct due to very low population numbers.

Step 2: Causes: This happens due to habitat loss, hunting, pollution, or climate change.

Step 3: Examples:

• Tiger (Panthera tigris)

• Great Indian Bustard (Ardeotis nigriceps)

Answer: Endangered animals are species that are at risk of extinction due to very low population numbers. Examples: Tiger and Great Indian Bustard.

Question 2: What are synthetic fibers? Give two examples.

Solution:

Step 1: Definition: Synthetic fibers are man-made fibers produced from chemical substances.

Step 2: Production: They are made by combining small molecules (monomers) to form long chains (polymers).

Step 3: Examples:

• Nylon

• Polyester

Answer: Synthetic fibers are man-made fibers produced from chemical substances by combining small molecules. Examples: Nylon and Polyester.

Question 3: Why does a wooden block float on water while an iron block sinks?

Solution:

Step 1: Principle: This is based on the principle of density and buoyancy.

Step 2: Wooden block: Density of wood is less than water (wood: ~0.5-0.8 g/cm³, water: 1 g/cm³), so it floats.

Step 3: Iron block: Density of iron is greater than water (iron: ~7.8 g/cm³), so it sinks.

Answer: Wood floats because its density is less than water, while iron sinks because its density is greater than water.

Question 4: What is electric current? Name its SI unit.

Solution:

Step 1: Definition: Electric current is the flow of electric charge through a conductor.

Step 2: Direction: It flows from positive to negative terminal in a circuit.

Step 3: SI Unit: The SI unit of electric current is Ampere (A).

Answer: Electric current is the flow of electric charge through a conductor. Its SI unit is Ampere (A).

Question 5: Differentiate between herbivores and carnivores with examples.

Solution:

Step 1: Herbivores: Animals that eat only plants and plant products.

Step 2: Carnivores: Animals that eat only meat (other animals).

Step 3: Examples:

Answer: Herbivores eat only plants (e.g., Cow, Goat), while carnivores eat only meat (e.g., Lion, Tiger).

Section C: Short Answer Questions (3-4 Marks Each)

Question 1: Draw a labeled diagram of a typical cell.

Solution:

Step 1: Basic Structure: A typical cell has three main parts:

Step 2: Diagram: Draw a simple cell with the following labels:

 Cell Membrane | +-----------+ | | | Nucleus |---- Nuclear Membrane | | | | Nucleolus| | | | Cytoplasm |---- Mitochondria | |---- Ribosomes | |---- Endoplasmic Reticulum +-----------+ 

Step 3: Functions:

• Cell Membrane: Controls entry and exit of substances

• Nucleus: Controls cell activities and contains DNA

• Cytoplasm: Jelly-like substance where cellular activities occur

• Mitochondria: Powerhouse of the cell, produces energy

Answer: [Diagram with proper labels and brief functions of each part]

Question 2: Why is storage of food grains essential? Name two structures for storage of grain.

Solution:

Step 1: Reasons for storage:

• To prevent spoilage and wastage

• To maintain supply throughout the year

• To protect from pests, insects, and rodents

• To maintain nutritional value

Step 2: Storage structures:

• Silos: Large cylindrical structures for bulk storage

• Granaries: Storehouse for storing grains

Step 3: Additional methods: Jute bags, metallic bins, etc.

Answer: Food grain storage is essential to prevent spoilage, maintain year-round supply, and protect from pests. Two structures: Silos and Granaries.

Question 3: Define thermoplastic and thermosetting materials with suitable examples.

Solution:

Step 1: Thermoplastic:

• Definition: Plastics that can be heated and reshaped multiple times

• Property: Softens on heating and hardens on cooling

• Examples: Polyethylene, PVC, Polystyrene

Step 2: Thermosetting:

• Definition: Plastics that cannot be reshaped once set

• Property: Undergoes permanent chemical change on heating

• Examples: Bakelite, Melamine, Formica

Step 3: Key difference: Thermoplastic can be recycled, thermosetting cannot.

Answer: Thermoplastic can be reshaped on heating (e.g., PVC), while thermosetting cannot be reshaped once set (e.g., Bakelite).

Question 4: What are the different types of friction? Explain with examples.

Solution:

Step 1: Static Friction:

• Definition: Friction between surfaces at rest

• Example: A book resting on a table

Step 2: Sliding Friction:

• Definition: Friction when one surface slides over another

• Example: A box sliding on the floor

Step 3: Rolling Friction:

• Definition: Friction when an object rolls over a surface

• Example: A ball rolling on the ground

Step 4: Fluid Friction:

• Definition: Friction in liquids and gases

• Example: A fish swimming in water, air resistance on a moving car

Answer: Four types: Static (book on table), Sliding (box on floor), Rolling (ball on ground), and Fluid (fish in water).

Question 5: Explain the process of digestion in the human body, including the role of enzymes.

Solution:

Step 1: Mouth:

• Food is chewed and mixed with saliva

• Enzyme: Salivary amylase breaks down starch

Step 2: Stomach:

• Food is mixed with gastric juice

• Enzyme: Pepsin breaks down proteins

Step 3: Small Intestine:

• Pancreatic juice and bile are added

• Enzymes: Trypsin (proteins), Lipase (fats), Amylase (carbohydrates)

Step 4: Absorption:

• Digested food is absorbed through intestinal walls

• Nutrients enter bloodstream

Step 5: Large Intestine:

• Water absorption and waste formation

Answer: Digestion involves mechanical and chemical breakdown of food using enzymes like amylase, pepsin, and lipase at different stages.

Section D: Long Answer Questions (5 Marks Each)

Question 1: Write any five characteristics of synthetic fibers.

Solution:

Step 1: Characteristic 1 - Durability:

• Synthetic fibers are more durable and long-lasting than natural fibers

• They do not wear out easily

Step 2: Characteristic 2 - Water Resistance:

• They do not absorb water easily

• Dry quickly after washing

Step 3: Characteristic 3 - Wrinkle Resistance:

• Do not wrinkle easily

• Maintain their shape better

Step 4: Characteristic 4 - Cost-effective:

• Generally cheaper than natural fibers

• Mass production makes them affordable

Step 5: Characteristic 5 - Chemical Resistance:

• Resistant to acids, bases, and other chemicals

• Not easily damaged by chemicals

Answer: Five characteristics: Durability, Water resistance, Wrinkle resistance, Cost-effectiveness, and Chemical resistance.

Question 2: What is fuel? Write four characteristics of an ideal fuel.

Solution:

Step 1: Definition of Fuel:

• Fuel is a substance that burns in air to produce heat and light energy

• It is used for various purposes like cooking, heating, and transportation

Step 2: Characteristic 1 - High Calorific Value:

• Should produce large amount of energy per unit mass

• More energy means better efficiency

Step 3: Characteristic 2 - Easy Availability:

• Should be easily available and accessible

• Should not be rare or difficult to obtain

Step 4: Characteristic 3 - Clean Burning:

• Should burn completely without producing harmful smoke or gases

• Should not cause air pollution

Step 5: Characteristic 4 - Safe Storage and Transport:

• Should be easy to store and transport

• Should not be explosive or dangerous to handle

Answer: Fuel produces heat and light energy when burned. Ideal fuel characteristics: High calorific value, Easy availability, Clean burning, Safe storage and transport.

Question 3: Draw a labeled diagram of the male or female reproductive organ of a human.

Solution:

Step 1: Choose reproductive system: Female reproductive system

Step 2: Diagram:

 Female Reproductive System Fallopian Tubes | +-----+-----+ | | Ovary Ovary | | +-----+-----+ | Uterus | Cervix | Vagina 

Step 3: Functions:

• Ovaries: Produce eggs (ova) and hormones

• Fallopian Tubes: Transport eggs from ovaries to uterus

• Uterus: Where fetus develops during pregnancy

• Cervix: Lower part of uterus

• Vagina: Birth canal

Step 4: Additional information:

• Menstruation occurs when egg is not fertilized

• Fertilization usually occurs in fallopian tubes

Answer: [Properly labeled diagram with functions of each part]

Question 4: What is acid rain? How does it affect buildings, plants, and water bodies?

Solution:

Step 1: Definition of Acid Rain:

• Acid rain is rainfall that has become acidic due to air pollution

• Formed when sulfur dioxide and nitrogen oxides react with water in atmosphere

• pH of acid rain is less than 5.6

Step 2: Effects on Buildings:

• Corrodes limestone, marble, and metal structures

• Damages historical monuments (e.g., Taj Mahal)

• Weakens concrete and paint

Step 3: Effects on Plants:

• Damages leaves by destroying waxy coating

• Reduces photosynthesis efficiency

• Affects soil chemistry, making nutrients unavailable

• Stunts plant growth and can kill trees

Step 4: Effects on Water Bodies:

• Lowers pH of lakes and rivers

• Kills fish and other aquatic life

• Disrupts aquatic food chains

• Makes water unsuitable for drinking

Step 5: Prevention:

• Reduce industrial emissions

• Use clean energy sources

• Install pollution control devices

Answer: Acid rain is acidic rainfall (pH < 5.6) formed from air pollutants. It corrodes buildings, damages plants by affecting leaves and soil, and kills aquatic life by lowering water pH.

Question 5: Write down five differences between plant and animal cells.

Solution:

Step 1: Structural differences analysis:

Step 2: Functional implications:

• Cell wall provides structural support to plants

• Chloroplasts enable plants to make their own food

• Large vacuoles help maintain plant shape and store water

• Animals have flexible cell membrane for movement

• Animal cells can change shape more easily

Answer: Five differences: Cell wall (present in plants, absent in animals), Chloroplasts (present in plants only), Vacuoles (large in plants, small in animals), Shape (fixed in plants, flexible in animals), Nutrition (autotrophic in plants, heterotrophic in animals).

Note: These solutions cover all major topics of CBSE Class 8 Science including Biology, Chemistry, and Physics concepts as per the latest exam pattern.