CBSE Class 10 Science Important Questions

1. What is the law of conservation of mass? How is it demonstrated in a chemical reaction?

Answer: The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. This is demonstrated when the mass of the reactants equals the mass of the products. For example, in the reaction between hydrogen and oxygen to form water:
2H₂ + O₂ → 2H₂O
Here, the mass of hydrogen and oxygen before the reaction equals the mass of water produced after the reaction.

2. Explain the mechanism of the human eye and how defects in the eye can be corrected.

Answer: The human eye functions like a camera. Light enters through the cornea, passes through the pupil, and is focused on the retina by the lens. The retina sends signals to the brain through the optic nerve. Defects like myopia (short-sightedness) can be corrected using concave lenses, and hypermetropia (long-sightedness) can be corrected using convex lenses.

3. Describe the process of photosynthesis and the role of chlorophyll.

Answer: Photosynthesis is the process by which green plants make their food using sunlight, carbon dioxide, and water. Chlorophyll, present in the chloroplasts of leaf cells, captures sunlight to convert it into chemical energy, which drives the process. The overall equation for photosynthesis is:
6CO₂ + 6H₂O + Light energy → C₆H₁₂O₆ + 6O₂
(Glucose is produced, and oxygen is released as a by-product.)

4. What are the different types of chemical reactions with examples?

Answer: The main types of chemical reactions are:

• Combination Reaction: Two or more substances combine to form one product.
  Example: 2H₂ + O₂ → 2H₂O

• Decomposition Reaction: A compound breaks down into simpler substances.
  Example: 2H₂O → 2H₂ + O₂

• Displacement Reaction: One element displaces another in a compound.
  Example: Zn + CuSO₄ → ZnSO₄ + Cu

• Double Displacement Reaction: Two compounds exchange ions.
  Example: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

5. How does the magnetic effect of electric current work? Explain with an example.

Answer: The magnetic effect of electric current, also known as electromagnetism, occurs when an electric current passes through a conductor, generating a magnetic field around it. This can be demonstrated using a solenoid (a coil of wire). When electric current passes through the solenoid, it behaves like a magnet, attracting iron objects. An example is the working of an electromagnet or electric bell.

6. What are the major differences between ionic and covalent bonds?

Answer:

• Ionic Bond: Formed when electrons are transferred from one atom to another, creating ions.
  Example: NaCl (Sodium Chloride)

• Covalent Bond: Formed when two atoms share one or more pairs of electrons.
  Example: H₂O (Water)

Ionic bonds are typically stronger than covalent bonds, and ionic compounds have higher melting and boiling points.

7. Explain the structure of the heart and its functioning in detail.

Answer: The heart is a four-chambered organ with two atria and two ventricles. The right atrium receives deoxygenated blood from the body and pumps it into the right ventricle, which sends it to the lungs for oxygenation. The left atrium receives oxygenated blood from the lungs and pumps it into the left ventricle, which sends it to the rest of the body. The heart functions through rhythmic contractions regulated by the pacemaker.

8. What is the importance of the carbon cycle in the environment?

Answer: The carbon cycle is essential for regulating Earth's climate and sustaining life. It involves the exchange of carbon between the atmosphere, oceans, and living organisms. Plants absorb carbon dioxide during photosynthesis and convert it into organic matter, which is passed through the food chain. Carbon returns to the atmosphere through respiration, decomposition, and combustion, maintaining a balance in the ecosystem.

9. Explain Mendel’s laws of inheritance with an example.

Answer: Mendel’s laws of inheritance include:

• Law of Dominance: In a cross of parents that are pure for contrasting traits, only the dominant trait appears in the next generation.

• Law of Segregation: Alleles separate during gamete formation, ensuring each gamete carries only one allele for each trait.

• Law of Independent Assortment: Genes for different traits segregate independently.

For example, when a pure tall pea plant (TT) is crossed with a pure dwarf plant (tt), all offspring in the F₁ generation are tall (Tt), showing the dominance of the tall trait.

10. What is the importance of sustainable management of natural resources?

Answer: Sustainable management ensures that natural resources are used wisely and conserved for future generations. It helps maintain ecological balance, prevents resource depletion, and promotes biodiversity. Sustainable practices include reforestation, water conservation, and reducing pollution. These steps are crucial to avoid the overuse of resources, ensuring their availability for future generations.

How Does Class 10 Science Important Questions Help You with Exams?

Physics:

• Thorough Understanding of Concepts: Focuses on important physics topics like electric circuits, light, and magnetism, ensuring clarity of fundamental concepts.

• Improves Problem-Solving Skills: Enhances the ability to solve numerical problems and conceptual questions related to topics like the magnetic effect of current and ray diagrams.

• Prepares for Application-Based Questions: Helps students practice real-life application-based questions, such as those involving electrical devices and optical instruments.

Chemistry:

• Covers Key Chemical Reactions: Focuses on frequently asked questions related to chemical reactions, periodic table, and bonding, ensuring students grasp key chemical principles.

• Conceptual Clarity: Strengthens understanding of core topics like acid-base reactions, metals and non-metals, and organic chemistry.

• Prepares for Practical-Based Questions: Assists in preparing for practical-based questions on chemical reactions, ensuring familiarity with experimental procedures and observations.

Biology:

• Enhances Knowledge of Life Processes: Focuses on essential biological processes such as photosynthesis, respiration, and digestion, aiding in clear understanding of the human body and plants.

• Promotes Understanding of Heredity and Evolution: Helps students learn Mendel’s laws of inheritance and evolutionary principles, which are often part of important exam questions.

• Prepares for Environmental Science Topics: Covers important topics on ecosystems, sustainable resource management, and environmental conservation, emphasizing their real-world relevance.

Additional Study Materials for Class 10 Science