Class 10 NCERT Science
Class 10 NCERT Science is a comprehensive textbook designed to provide students with a solid foundation in various scientific concepts and principles. The book is structured to promote a deeper understanding of science through a mix of theoretical explanations, practical experiments, and real-life applications. The content is divided into four main sections: Physics, Chemistry, Biology, and Environmental Science, each offering a detailed exploration of different topics.
Physics
The Physics section of the Class 10 NCERT Science book covers fundamental concepts such as light, electricity, and the sources of energy. It includes chapters on reflection and refraction of light, the human eye, and the colorful world, electric current and its effects, and the management of natural resources. The focus is on understanding physical phenomena and their applications in daily life. Key experiments and activities are included to help students grasp the practical aspects of physics.
Chemistry
The Chemistry section delves into the composition, behavior, and properties of matter. Key topics include chemical reactions and equations, acids, bases and salts, metals and non-metals, carbon and its compounds, and the periodic classification of elements. The chapters are designed to help students understand the fundamental principles of chemistry, including the structure of atoms, the periodic table, and chemical bonding. Practical experiments and activities reinforce the theoretical concepts and promote scientific thinking.
Biology
The Biology section covers a wide range of topics related to living organisms and life processes. It includes chapters on life processes, control and coordination, how do organisms reproduce, heredity and evolution, and our environment. The emphasis is on understanding the structure and functions of various biological systems, genetic inheritance, and the impact of human activities on the environment. The chapters are enriched with diagrams, activities, and experiments to make the learning experience engaging and interactive.
Environmental Science
This section addresses the various environmental issues and the importance of sustainable management of natural resources. It includes chapters on sustainable management of natural resources, the concept of an ecosystem, biodiversity, and the impact of human activities on the environment. The objective is to raise awareness among students about environmental conservation and the importance of sustainable development.
Pedagogical Approach
The Class 10 NCERT Science textbook adopts a student-centered pedagogical approach, encouraging inquiry-based learning and critical thinking. Each chapter begins with an introduction to the topic, followed by detailed explanations, diagrams, and illustrations to aid understanding. The chapters conclude with exercises, activities, and project work to reinforce the concepts learned. The textbook also includes real-life examples and case studies to help students connect scientific concepts with everyday life.
Importance and Relevance
The Class 10 NCERT Science book is an essential resource for students preparing for their board examinations. It provides a strong foundation for higher studies in science and related fields. The book is also aligned with the latest educational standards and guidelines, ensuring that students receive up-to-date and relevant knowledge. By promoting a scientific temperament and encouraging problem-solving skills, the book aims to prepare students for future academic and career pursuits in the field of science.
Welcome to United Academy’s Class 10 NCERT Science Online Class! Our meticulously crafted online program is designed to provide students with an in-depth understanding of fundamental scientific concepts, ensuring a solid foundation for academic success. At United Academy, we understand the importance of quality education and have tailored our classes to align perfectly with the NCERT curriculum. Our experienced faculty, interactive teaching methods, and comprehensive study materials make learning science engaging and effective.
Whether you are exploring the intriguing principles of Physics, unraveling the complexities of Chemistry, or delving into the fascinating world of Biology, our online classes offer a holistic learning experience. We incorporate a blend of theoretical lessons, practical demonstrations, and real-life applications to help students grasp concepts easily and retain knowledge effectively. Join United Academy and embark on a journey of scientific discovery, where learning is not just about memorizing facts but understanding the world around us. Prepare to excel in your board examinations and beyond with United Academy’s Class 10 NCERT Science Online Class!
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Today Class Notes
Introduction to Metals and Non-Metals
- Classification: The chapter begins by classifying elements into metals and non-metals based on their physical and chemical properties.
- Examples: Common examples of metals include iron, copper, aluminum, and gold, while non-metals include elements like oxygen, sulfur, and carbon.
Physical Properties of Metals and Non-Metals
- Metals:
- Luster: Metals have a shiny appearance.
- Malleability: Metals can be hammered into thin sheets.
- Ductility: Metals can be drawn into wires.
- Conductivity: Metals are good conductors of heat and electricity.
- Density and Hardness: Metals generally have high density and are hard.
- Non-Metals:
- Luster: Non-metals lack luster and appear dull.
- Malleability and Ductility: Non-metals are neither malleable nor ductile.
- Conductivity: Non-metals are poor conductors of heat and electricity.
- Physical State: Non-metals can be solid, liquid, or gas at room temperature.
Chemical Properties of Metals and Non-Metals
- Reaction with Oxygen:
- Metals form basic oxides (e.g., magnesium oxide).
- Non-metals form acidic or neutral oxides (e.g., carbon dioxide).
- Reaction with Water:
- Some metals react with water to form metal hydroxides and hydrogen gas (e.g., sodium with water).
- Non-metals generally do not react with water.
- Reaction with Acids:
- Metals react with acids to form salts and hydrogen gas (e.g., zinc with hydrochloric acid).
- Non-metals do not usually react with acids.
- Reaction with Bases:
- Some metals react with strong bases to form complex compounds.
- Non-metals generally do not react with bases.
Reactivity Series
- Definition: The reactivity series is a list of metals arranged in order of decreasing reactivity.
- Importance: It helps predict how metals will react with other substances.
Occurrence and Extraction of Metals
- Occurrence: Metals are found in the earth’s crust and are extracted from ores.
- Extraction Methods: The extraction methods depend on the metal’s reactivity and include techniques such as mining, heating, and electrolysis.
Corrosion
- Definition: Corrosion is the gradual deterioration of metals due to chemical reactions with their environment (e.g., rusting of iron).
- Prevention: Methods to prevent corrosion include painting, galvanization, and alloying.
Uses of Metals and Non-Metals
- Metals: Used in construction, electrical wiring, utensils, machinery, and transportation due to their strength, conductivity, and durability.
- Non-Metals: Used in industries, fertilizers, water purification, and as essential components in biological processes.
Class 10 Science
Very Short Answer Type Questions
1. What are amphoteric oxides? Give two examples.
o Amphoteric oxides are oxides that can react with both acids and bases to form salt and water. Examples include aluminum oxide (Al₂O₃) and zinc oxide (ZnO).
2. Name the most malleable and ductile metal.
o Gold (Au) is the most malleable and ductile metal.
3. Why is sodium stored in kerosene oil?
o Sodium is stored in kerosene oil to prevent it from reacting with moisture and oxygen in the air, which can cause it to ignite or explode.
4. Give an example of a metal which is liquid at room temperature.
o Mercury (Hg) is a metal that is liquid at room temperature.
5. Which non-metal is a good conductor of electricity?
o Graphite (a form of carbon) is a non-metal that is a good conductor of electricity.
6. Name two metals which are found in nature in the free state.
o Gold (Au) and platinum (Pt) are two metals found in nature in the free state.
Short Answer Type Questions
1. Explain why ionic compounds have high melting and boiling points.
o Ionic compounds have high melting and boiling points because the strong electrostatic forces of attraction between the oppositely charged ions require a large amount of energy to break.\
o
2. What happens when a metal reacts with dilute hydrochloric acid? Write a balanced chemical equation for the reaction.
o When a metal reacts with dilute hydrochloric acid, it forms a metal chloride and hydrogen gas. For example, when zinc reacts with hydrochloric acid:
Zn+2HCl→ZnCl2+H2
3. Why do ionic compounds conduct electricity in the molten state but not in the solid state?
o Ionic compounds conduct electricity in the molten state because the ions are free to move. In the solid state, the ions are held in fixed positions and cannot move, so they do not conduct electricity.
4. Differentiate between metals and non-metals based on their physical properties.
o Metals are generally malleable, ductile, lustrous, and good conductors of heat and electricity. Non-metals are brittle, non-ductile, lack luster, and are poor conductors of heat and electricity.
5. Why do metals not evolve hydrogen gas with nitric acid?
o Metals do not evolve hydrogen gas with nitric acid because nitric acid is a strong oxidizing agent. It oxidizes the hydrogen produced to water and itself gets reduced to nitrogen oxides.
6. Explain the formation of ionic bonds with examples.
o Ionic bonds are formed when one atom donates an electron to another atom, resulting in the formation of positive and negative ions which attract each other. For example, in sodium chloride (NaCl), sodium (Na) donates an electron to chlorine (Cl), forming Na⁺ and Cl⁻ ions which attract each other to form NaCl.
7. Why do metals generally conduct electricity while non-metals do not?
o Metals conduct electricity because they have free electrons that can move through the metal lattice. Non-metals do not have free electrons and therefore do not conduct electricity.
Long Answer Type Questions
1. Describe the process of electrolytic refining of a metal with the help of a diagram.
o Electrolytic refining is a process used to purify metals. In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. An electrolyte solution of the metal salt is used. When an electric current is passed, the pure metal from the anode dissolves into the electrolyte and deposits on the cathode, leaving impurities behind or forming a sludge.
2. Explain the reactivity series of metals. How is it useful in predicting the outcome of a reaction between a metal and a salt solution?
o The reactivity series of metals is a list of metals arranged in order of their decreasing reactivity. It helps in predicting which metals will displace others in a reaction. A metal higher in the reactivity series will displace a metal lower in the series from its salt solution.
Example:
Zn+CuSO4→ZnSO4+Cu
3. Discuss the physical and chemical properties of metals and non-metals. Give examples to support your answer.
o Physical properties of metals:
Malleable (e.g., Gold)
Ductile (e.g., Copper)
Good conductors of heat and electricity (e.g., Silver)
Lustrous (e.g., Aluminium)
Chemical properties of metals:
React with acids to form salts and hydrogen gas (e.g., Magnesium with HCl)
Form basic oxides (e.g., Sodium oxide)
Physical properties of non-metals:
Brittle (e.g., Sulphur)
Poor conductors of heat and electricity (e.g., Phosphorus)
Non-lustrous (e.g., Carbon in the form of coal)
Chemical properties of non-metals:
React with oxygen to form acidic oxides (e.g., Sulphur dioxide)
Do not react with acids or bases (e.g., Nitrogen)
4. Describe the reactions of metals with water, acids, and bases. Give suitable examples for each type of reaction.
o Reactions with water:
Metals like sodium react vigorously with water to form sodium hydroxide and hydrogen gas.
2Na+2H2O→2NaOH+H2
Metals like iron react slowly with water to form iron oxide and hydrogen gas.
3Fe+4H2O→Fe3O4+4H2
o Reactions with acids:
Metals react with dilute acids to form a salt and hydrogen gas. Mg+2HCl→MgCl2+H2
o Reactions with bases:
Some metals like zinc react with bases like sodium hydroxide to form complex salts and hydrogen gas. Zn+2NaOH→Na2ZnO2+H2
Previous Year Board Questions
1. (CBSE 2018) Write a balanced chemical equation for the reaction of iron with steam. Name the product obtained.
3Fe+4H2O→Fe3O4+4H2
o The product obtained is iron (II,III) oxide, Fe₃O₄.
2. (CBSE 2017) Differentiate between the reactions of magnesium and zinc with dilute hydrochloric acid.
o Both magnesium and zinc react with dilute hydrochloric acid to form their respective chlorides and hydrogen gas, but magnesium reacts more vigorously than zinc.
Mg+2HCl→MgCl2+H2
Zn+2HCl→ZnCl2+H2
3. (CBSE 2016) Explain why calcium starts floating when added to water. Write the chemical equation for the reaction.
o Calcium starts floating on water because the hydrogen gas formed during the reaction sticks to its surface, making it buoyant.
Ca+2H2O→Ca(OH)2+H2
4. (CBSE 2015) How are metals extracted from their ores? Explain with an example.
o Metals are extracted from their ores through processes like roasting, reduction, and electrolysis. For example, iron is extracted from its ore (haematite) by reduction with carbon in a blast furnace.
Fe2O3+3C→2Fe+3CO
Class 10 Science Chapter 3 MCQ Question with Answer
Based on the content of Class 10 NCERT Science Chapter 3 “Metals and Non-Metals,” here are 30 multiple-choice questions (MCQs) along with their answers:
1. Which of the following is a property of metals?
o a) Poor conductor of heat
o b) Brittle
o c) Dull
o d) Malleable
o Answer: d) Malleable
2. Which metal is liquid at room temperature?
o a) Sodium
o b) Mercury
o c) Aluminum
o d) Iron
o Answer: b) Mercury
3. Which of the following is a non-metal that is a good conductor of electricity?
o a) Carbon (in the form of graphite)
o b) Sulphur
o c) Phosphorus
o d) Iodine
o Answer: a) Carbon (in the form of graphite)
4. Which of the following is the most reactive metal?
o a) Gold
o b) Silver
o c) Sodium
o d) Platinum
o Answer: c) Sodium
5. The ability of metals to be drawn into thin wires is known as:
o a) Malleability
o b) Ductility
o c) Conductivity
o d) Sonority
o Answer: b) Ductility
6. What is the main ore of aluminum?
o a) Bauxite
o b) Hematite
o c) Galena
o d) Magnetite
o Answer: a) Bauxite
7. Which of the following metals does not react with water at all?
o a) Sodium
o b) Calcium
o c) Magnesium
o d) Lead
o Answer: d) Lead
8. The property of metals by which they can be beaten into thin sheets is called:
o a) Malleability
o b) Ductility
o c) Conductivity
o d) Brittleness
o Answer: a) Malleability
9. Which non-metal is essential for the production of proteins in plants?
o a) Phosphorus
o b) Nitrogen
o c) Sulphur
o d) Chlorine
o Answer: b) Nitrogen
10. Which of the following metals forms an amphoteric oxide?
o a) Sodium
o b) Calcium
o c) Aluminum
o d) Iron
o Answer: c) Aluminum
11. Which metal is used in galvanization to prevent rusting of iron?
o a) Zinc
o b) Copper
o c) Tin
o d) Lead
o Answer: a) Zinc
12. What is the chemical formula for rust?
o a) FeO
o b) Fe2O3
o c) Fe3O4
o d) FeO2
o Answer: b) Fe2O3
13. Which gas is produced when metals react with acids?
o a) Oxygen
o b) Carbon dioxide
o c) Hydrogen
o d) Nitrogen
o Answer: c) Hydrogen
14. Which of the following is a metal that does not react with cold water, hot water, or steam?
o a) Potassium
o b) Sodium
o c) Gold
o d) Calcium
o Answer: c) Gold
15. Which of the following non-metals is used to make the tips of matches?
o a) Carbon
o b) Phosphorus
o c) Sulphur
o d) Chlorine
o Answer: b) Phosphorus
16. Which of the following is not an alloy?
o a) Brass
o b) Bronze
o c) Steel
o d) Copper
o Answer: d) Copper
17. Which metal is used in making the filaments of electric bulbs?
o a) Copper
o b) Iron
o c) Tungsten
o d) Aluminum
o Answer: c) Tungsten
18. Which of the following metals can displace hydrogen from acids?
o a) Copper
o b) Silver
o c) Gold
o d) Zinc
o Answer: d) Zinc
19. The process of coating iron with zinc to prevent rusting is called:
o a) Alloying
o b) Galvanization
o c) Anodizing
o d) Electroplating
o Answer: b) Galvanization
20. Which non-metal is used in the purification of drinking water?
o a) Chlorine
o b) Sulphur
o c) Phosphorus
o d) Nitrogen
o Answer: a) Chlorine
21. Which of the following is a property of non-metals?
o a) Lustrous
o b) Malleable
o c) Poor conductor of heat
o d) Ductile
o Answer: c) Poor conductor of heat
22. Which of the following metals is the best conductor of electricity?
o a) Gold
o b) Silver
o c) Copper
o d) Aluminum
o Answer: b) Silver
23. Which non-metal is essential for respiration?
o a) Nitrogen
o b) Carbon dioxide
o c) Oxygen
o d) Helium
o Answer: c) Oxygen
24. Which of the following metals is used in making aircraft bodies?
o a) Iron
o b) Zinc
o c) Aluminum
o d) Copper
o Answer: c) Aluminum
25. Which of the following non-metals is used in the vulcanization of rubber?
o a) Sulphur
o b) Phosphorus
o c) Nitrogen
o d) Chlorine
o Answer: a) Sulphur
26. Which metal is used in the manufacturing of stainless steel?
o a) Tin
o b) Zinc
o c) Chromium
o d) Lead
o Answer: c) Chromium
27. Which of the following is an alloy of copper and zinc?
o a) Bronze
o b) Brass
o c) Steel
o d) Solder
o Answer: b) Brass
28. Which of the following metals is least reactive?
o a) Potassium
o b) Calcium
o c) Gold
o d) Magnesium
o Answer: c) Gold
29. Which gas is evolved when zinc reacts with dilute sulphuric acid?
o a) Oxygen
o b) Nitrogen
o c) Hydrogen
o d) Carbon dioxide
o Answer: c) Hydrogen
30. Which of the following is a property of ionic compounds?
o a) Low melting points
o b) High electrical conductivity in solid state
o c) Soluble in water
o d) Poor electrical conductivity in molten state
o Answer: c) Soluble in water
These questions cover a variety of key concepts from the chapter on metals and non-metals, ensuring a comprehensive review of the NCERT study material specially made for Class 10.
Class 10 NCERT Science Chapter 3 "Metals and Non-Metals"
Here are some theory questions and answers based on the content of Class 10 NCERT Science Chapter 3 “Metals and Non-Metals” that align with the CBSE public exam model:
Question 1:
Explain the reaction of metals with acids. What is the common characteristic of these reactions? Provide a balanced chemical equation to support your explanation.
Answer:
Metals react with acids to produce a salt and hydrogen gas. This reaction is characterized by the release of hydrogen gas, which can be observed as bubbles forming in the acid solution. The general reaction can be represented as:
Metal+Dilute Acid→Salt+Hydrogen Gas
For example, the reaction of zinc with hydrochloric acid is:
Zn+2HCl→ZnCl2+H2
In this reaction:
• Zinc (Zn) reacts with hydrochloric acid (HCl).
• Zinc chloride (ZnCl2) is formed as the salt.
• Hydrogen gas (H2) is released.
Question 2:
Describe the physical properties of metals and non-metals. Mention any two properties where metals differ significantly from non-metals.
Answer:
Physical Properties of Metals:
1. Metals are generally solid at room temperature (except mercury, which is liquid).
2. They have a shiny appearance (lustrous).
3. Metals are good conductors of heat and electricity.
4. They are malleable (can be hammered into thin sheets).
5. Metals are ductile (can be drawn into wires).
Physical Properties of Non-Metals:
1. Non-metals can be solid, liquid, or gas at room temperature.
2. They generally have a dull appearance.
3. Non-metals are poor conductors of heat and electricity.
4. They are brittle in solid form and break easily (not malleable or ductile).
Two Properties where Metals Differ Significantly from Non-Metals:
1. Conductivity:
o Metals are good conductors of heat and electricity, which allows them to be used in electrical wiring and cookware.
o Non-metals are poor conductors of heat and electricity, which makes them suitable as insulators.
2. Malleability and Ductility:
o Metals are malleable and ductile, allowing them to be shaped into various forms without breaking.
o Non-metals are brittle in their solid state and break easily when subjected to force, hence they cannot be shaped like metals.
Question 3:
What is an alloy? Give two examples and mention their composition and uses.
Answer:
An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. Alloys are created to enhance the properties of the constituent elements, such as strength, durability, and resistance to corrosion.
Examples:
1. Brass:
o Composition: Copper (Cu) and Zinc (Zn)
o Uses: Used in the manufacture of musical instruments, decorative items, and plumbing fittings due to its acoustic properties and resistance to corrosion.
2. Stainless Steel:
o Composition: Iron (Fe), Chromium (Cr), Nickel (Ni), and Carbon (C)
o Uses: Widely used in kitchen utensils, surgical instruments, and construction materials because of its resistance to rust and staining.
Question 4:
Explain the process of extraction of metals from their ores. Describe the steps involved in the extraction of a metal of medium reactivity, such as iron.
Answer:
The extraction of metals from their ores involves several steps, depending on the reactivity of the metal. For a metal of medium reactivity, such as iron, the process includes the following steps:
1. Concentration of Ore:
o The ore is crushed and ground to remove impurities. Methods such as magnetic separation or froth flotation are used to concentrate the ore.
2. Reduction of the Ore:
o The concentrated ore is reduced to extract the metal. For iron, this is done in a blast furnace using carbon (in the form of coke) as the reducing agent.
o The chemical reaction for the reduction of iron ore (hematite) is: Fe2O3+3C→2Fe+3CO
3. Purification of Metal:
o The extracted metal is purified to remove any remaining impurities. For iron, this can involve processes such as electrolysis or the use of a basic oxygen furnace.
Question 5:
Discuss the importance of reactivity series in the extraction of metals. How does the position of a metal in the reactivity series influence its extraction method?
Answer:
The reactivity series is a list of metals arranged in order of their reactivity, from the most reactive to the least reactive. This series is crucial in determining the method used for the extraction of metals from their ores.
• Highly Reactive Metals (e.g., Sodium, Potassium, Calcium):
o These metals are extracted by electrolysis of their molten chlorides or oxides because they cannot be reduced by carbon.
• Metals of Medium Reactivity (e.g., Zinc, Iron, Lead):
o These metals are usually extracted by reducing their oxides with carbon or carbon monoxide in a blast furnace.
• Less Reactive Metals (e.g., Copper, Mercury, Gold):
o These metals are found in their free or native state and can be extracted by simple physical methods or by heating their ores in the presence of air.
The position of a metal in the reactivity series determines its reactivity with other substances and the complexity of the extraction process. Metals higher up in the series require more energy-intensive methods such as electrolysis, while those lower down can be extracted using simpler reduction methods.
Class 10 CBSE Science Chapter 3 notes
Here are some Assertion and Reason questions based on Class 10 NCERT Science Chapter 3 “Metals and Non-Metals”:
Question 1:
Assertion (A): Gold and silver are used to make jewelry.
Reason (R): Gold and silver are highly reactive metals.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: c) A is true, but R is false.
Question 2:
Assertion (A): Aluminum is used in the manufacturing of aircraft.
Reason (R): Aluminum has a very high density.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: c) A is true, but R is false.
Question 3:
Assertion (A): Sodium is stored in kerosene.
Reason (R): Sodium is highly reactive and reacts with water vapor present in the air.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: a) Both A and R are true, and R is the correct explanation of A.
Question 4:
Assertion (A): Iron nails dipped in copper sulphate solution turn brownish.
Reason (R): Iron displaces copper from copper sulphate solution.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: a) Both A and R are true, and R is the correct explanation of A.
Question 5:
Assertion (A): Metals are good conductors of electricity.
Reason (R): Metals have free electrons that can move through the metal lattice.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: a) Both A and R are true, and R is the correct explanation of A.
Question 6:
Assertion (A): Zinc does not react with cold water.
Reason (R): Zinc is less reactive than hydrogen.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: b) Both A and R are true, but R is not the correct explanation of A.
Question 7:
Assertion (A): Copper is used in making electrical wires.
Reason (R): Copper has a low melting point.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: c) A is true, but R is false.
Question 8:
Assertion (A): Non-metals are generally brittle.
Reason (R): Non-metals have high melting and boiling points.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: c) A is true, but R is false.
Question 9:
Assertion (A): Graphite is a good conductor of electricity.
Reason (R): Graphite is an allotrope of carbon.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: b) Both A and R are true, but R is not the correct explanation of A.
Question 10:
Assertion (A): Magnesium ribbon should be cleaned before burning in air.
Reason (R): Magnesium reacts with oxygen to form magnesium oxide which is a white powder.
• a) Both A and R are true, and R is the correct explanation of A.
• b) Both A and R are true, but R is not the correct explanation of A.
• c) A is true, but R is false.
• d) A is false, but R is true.
Answer: b) Both A and R are true, but R is not the correct explanation of A.
These questions test the understanding of the relationship between assertions and reasons, requiring students to critically evaluate both statements and their connection.
Class 10 ncert science chapter 3 question and answer
Here are some 2-mark questions and their answers based on Class 10 NCERT Science Chapter 3 “Metals and Non-Metals”:
Question 1:
State two physical properties each of metals and non-metals.
Answer:
Physical Properties of Metals:
- Malleability: Metals can be hammered into thin sheets without breaking.
- Ductility: Metals can be drawn into wires.
Physical Properties of Non-Metals:
- Brittleness: Non-metals break easily when hammered, hence they are not malleable or ductile.
- Poor Conductors: Non-metals are poor conductors of heat and electricity, except for graphite.
Question 2:
What is an alloy? Give one example and its composition.
Answer:
An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, designed to have specific properties.
Example:
- Bronze: Composed of copper (Cu) and tin (Sn).
Question 3:
Why do ionic compounds have high melting and boiling points?
Answer:
Ionic compounds have high melting and boiling points because they consist of ions held together by strong electrostatic forces of attraction (ionic bonds). A large amount of energy is required to break these strong bonds, resulting in high melting and boiling points.
Question 4:
Explain why metals are good conductors of electricity.
Answer:
Metals are good conductors of electricity because they have free electrons that can move easily through the metal lattice. When a potential difference is applied across a metal, these free electrons flow, allowing electric current to pass through.
Question 5:
Why is sodium stored in kerosene?
Answer:
Sodium is highly reactive and reacts vigorously with water and oxygen in the air. To prevent it from reacting and to protect it from moisture and air, sodium is stored in kerosene, which acts as a protective barrier.
Question 6:
Write the balanced chemical equation for the reaction of iron with steam.
Answer:
The balanced chemical equation for the reaction of iron with steam is: 3Fe+4H2O→Fe3O4+4H2
Question 7:
Name two amphoteric oxides and write their chemical formulas.
Answer:
Two amphoteric oxides are:
- Aluminum oxide (Al2O3)
- Zinc oxide (ZnO)
Question 8:
What happens when a metal reacts with a dilute acid? Write a general equation.
Answer:
When a metal reacts with a dilute acid, a salt and hydrogen gas are formed. The general equation for this reaction is:
Metal+Dilute Acid→Salt+Hydrogen Gas
For example, the reaction of zinc with hydrochloric acid:
Zn+2HCl→ZnCl2+H2
Question 9:
Why are non-metals not lustrous? Give an example of an exception.
Answer:
Non-metals are not lustrous because they do not have free electrons that can reflect light. Most non-metals have a dull appearance.
Exception: Iodine is a non-metal that has a lustrous appearance.
Question 10:
How does the reactivity of metals change in the reactivity series?
Answer:
In the reactivity series, the reactivity of metals decreases from top to bottom. Highly reactive metals, such as potassium and sodium, are at the top, while less reactive metals, such as gold and platinum, are at the bottom.
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