Introduction
Welcome to our comprehensive guide on Class 10 Science Chapter 3 Important Questions! As students embark on their academic journey, understanding key concepts in science is crucial for building a strong foundation. In this post, we will focus on Class 10 Science Chapter 3 Important Questions that delve into fascinating topics, enhancing your knowledge and preparing you for exams.
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Table of Contents
1. State two ways to prevent the rusting of iron.
Answer: Here are two effective ways to prevent the rusting of iron:
Cathodic Protection: This method uses a more reactive metal (like zinc) as a sacrificial anode. When connected to iron, the sacrificial metal corrodes instead of the iron, thus preventing rusting.
Coating: Applying a protective layer, such as paint, oil, or galvanization (zinc coating), helps shield iron from moisture and oxygen, which are necessary for rust to form.
2. Define mineral.
Answer: A mineral is a naturally occurring solid that is inorganic, has a specific chemical composition, and exhibits a crystalline structure. Minerals are the building blocks of rocks and can be found in various forms, such as single elements (like gold or copper) or compounds (like quartz or feldspar). They possess specific physical properties, including hardness, luster, color, and cleavage, which help their identification.
3. Define ore.
Answer: An ore is a naturally occurring rock or mineral from which valuable metals or minerals can be extracted profitably. Ores contain a high concentration of specific elements, such as gold, copper, iron, or aluminum, making them economically viable for mining and processing.
4. Define gangue.
Answer: Gangue refers to the unwanted or economically worthless material that is found alongside valuable minerals in an ore. It typically consists of minerals, rock fragments, or other materials that need to be removed during the processing of the ore to extract the desired metals or minerals. Reducing gangue is essential to improve the efficiency and cost-effectiveness of mining operations.
5. Platinum, gold, and silver are used to make jewelry.
Answer: Platinum, gold, and silver are used to make jewelry for several key reasons:
- Aesthetic Appeal: These metals have a beautiful luster and come in various colors, enhancing the visual appeal of jewelry.
- Durability: Platinum is particularly strong and resistant to tarnish, while gold and silver can be alloyed for added strength, making them suitable for everyday wear.
- Malleability: They are easy to shape and mold, allowing for intricate designs and detailed craftsmanship.
- Cultural Significance: Gold and silver have long been symbols of wealth and status in many cultures, while platinum is prized for its rarity and luxury.
- Hypoallergenic Properties: Many alloys of gold and platinum are less likely to cause allergic reactions, making them safe for sensitive skin.
6. Ionic compounds have high melting points.
Answer: Ionic compounds have high melting points due to the strong electrostatic forces of attraction between the positively and negatively charged ions in the crystal lattice structure. These forces, referred to as ionic bonds, necessitate a considerable amount of energy to be broken.
As a result, a high temperature is needed to overcome these strong attractions and allow the ions to move freely, which is necessary for the compound to melt. Additionally, the rigid structure of the ionic lattice contributes to the high melting points of these compounds.
7. Difference between calcination and roasting.
Answer: The differences between calcination and roasting are as follows:
Calcination
- Definition: Calcination is the process of heating an ore to a high temperature in the absence of air or oxygen.
- Purpose: Primarily used to remove volatile impurities, such as water or carbon dioxide, from a metal ore.
- Example: Heating limestone (calcium carbonate) to produce lime (calcium oxide) and carbon dioxide.
Roasting
- Definition: Roasting is the process of heating an ore in the presence of excess air or oxygen.
- Purpose: Used to oxidize sulfide ores, convert them to oxides, and remove sulfur as sulfur dioxide.
- Example: Heating chalcopyrite (copper sulfide) to convert it into copper oxide and sulfur dioxide.
Summary
In summary, calcination occurs in the absence of air to drive off volatile components, while roasting takes place in the presence of air to oxidize ores and remove impurities.
8. Define alloy and write some names of alloy, their composition and uses.
Answer: An alloy is a combination of two or more elements, with at least one of those elements being a metal. Alloys are created to enhance certain properties, such as strength, durability, or corrosion resistance.
Examples of Alloys
- Steel
- Composition: Iron (about 98%) and carbon (up to 2%).
- Uses: Construction, automotive, tools, and machinery due to its strength and versatility.
- Bronze
- Composition: Copper (about 88%) and tin (about 12%), though it can include other elements.
- Uses: Sculptures, musical instruments, and ship fittings, valued for its corrosion resistance and durability.
- Brass
- Composition: Copper (about 70-90%) and zinc (about 10-30%).
- Uses: Plumbing fittings, musical instruments, and decorative items due to its low friction and attractive appearance.
- Aluminum Alloy
- Composition: Aluminum (typically over 90%) with elements like copper, magnesium, or silicon.
- Uses: Aircraft, automotive parts, and packaging materials for its lightweight and strength.
- Stainless Steel
- Composition: Iron, carbon (up to 1%), and chromium (at least 10.5%).
- Uses: Kitchen utensils, medical instruments, and construction materials due to its corrosion resistance and strength.
These alloys are commonly used across various industries due to their improved properties compared to their individual components.
9. Physical properties of metals and non-metals.
Answer: Comparison of the physical properties of metals and non-metals:
Physical Properties of Metals
- Luster: Metals have a shiny appearance and reflect light well.
- Conductivity: Metals demonstrate excellent abilities to conduct heat and electricity.
- Malleability: Metals can be hammered or rolled into thin sheets without breaking.
- Ductility: They can be drawn into wires without losing strength.
- Density: Metals generally have high density and are heavy for their size.
- Melting and Boiling Points: Most metals possess high melting and boiling points.
Physical Properties of Non-Metals
- Dull Appearance: Non-metals lack the shiny luster characteristic of metals.
- Poor Conductivity: They are generally poor conductors of heat and electricity (with some exceptions like graphite).
- Brittleness: Non-metals are usually brittle in solid form and break easily.
- Not Malleable or Ductile: They cannot be easily shaped or drawn into wires.
- Low Density: Non-metals generally have lower densities than metals.
- Variable Melting and Boiling Points: Non-metals can have a wide range of melting and boiling points, often lower than those of metals.
These properties help distinguish metals from non-metals and contribute to their various applications in everyday life.
10. Chemical properties of metals and non-metals.
Answer: A breakdown of the chemical attributes of metals compared to non-metals:
Chemical Properties of Metals
- Reactivity: Metals tend to lose electrons during chemical reactions, forming positive ions (cations). Their reactivity varies widely; for example, alkali metals are highly reactive, while noble metals like gold are much less so.
- Oxides: Metals typically form basic oxides when they react with oxygen. For instance, magnesium oxide is basic and can react with acids to form salts.
- Acids and Bases: Metals can react with acids to generate hydrogen gas and salt. For example, when zinc interacts with hydrochloric acid, it yields zinc chloride and hydrogen gas.
- Alloy Formation: Metals can easily combine with one another to form alloys, enhancing their properties.
- Electro positivity: Metals exhibit electropositive behavior, meaning they readily lose electrons to form positive ions.
Chemical Properties of Non-Metals
- Reactivity: Non-metals tend to gain or share electrons in chemical reactions, forming negative ions (anions) or covalent compounds. Their reactivity varies; for example, halogens are highly reactive, while noble gases are mostly inert.
- Oxides: Non-metals generally produce acidic or neutral oxides upon reacting with oxygen. For example, carbon dioxide is classified as an acidic oxide.
- Acids and Bases: Non-metals can react with bases to form salts and water. For instance, sulfuric acid can react with sodium hydroxide to produce sodium sulfate and water.
- Covalent Bonding: Non-metals commonly form covalent bonds with each other by sharing electrons, resulting in molecular compounds.
- Electronegativity: Non-metals generally have high electronegativity, meaning they tend to attract electrons during chemical reactions.
These chemical properties highlight the distinct behaviors of metals and non-metals in various chemical reactions and their interactions with other elements.
11. Properties of ionic compounds.
Answer: key properties of ionic compounds:
1. High Melting and Boiling Points
Ionic compounds typically have high melting and boiling points due to the strong electrostatic forces of attraction between the positively and negatively charged ions in the lattice structure.
2. Solubility in Water
Many ionic compounds are soluble in water. The polar nature of water molecules can help separate and stabilize the ions in solution.
3. Electrical Conductivity
Ionic compounds are capable of conducting electricity when dissolved in water or a molten state, as the ions can move freely. However, they do not conduct electricity in their solid state because the ions are fixed in place within the lattice.
4. Brittleness
Ionic compounds tend to be brittle and may break apart when exposed to stress. When force is applied, like charges may align and repel each other, causing the structure to break.
5. Formation of Crystalline Solids
Ionic compounds form crystalline structures, which are characterized by a regular arrangement of ions in a repeating pattern, contributing to their distinct geometric shapes.
6. High Density
Many ionic compounds have relatively high densities compared to molecular compounds due to the close packing of ions in the crystal lattice.
7. Stability
Ionic compounds are generally stable at room temperature and can withstand various conditions without decomposing.
These properties make ionic compounds significant in various applications, including in the production of salts, ceramics, and electrolytes.
12. Difference between minerals and ores.
Answer: Comparison of minerals and ores:
Definition
- Minerals: Naturally occurring, inorganic substances with a definite chemical composition and crystalline structure. They can be elements or compounds.
- Ores: Specific types of minerals that contain valuable metals or minerals that can be extracted profitably. Ores are often composed of one or more minerals.
Economic Value
- Minerals: Not all minerals have economic value; many are simply components of rocks and do not yield useful materials.
- Ores: Ores have significant economic value because they contain a high concentration of valuable elements or compounds that can be mined and processed.
Processing
- Minerals: Minerals can exist in their pure form or as part of a larger rock structure and may require further processing to isolate the desired element.
- Ores: Ores typically undergo extraction processes (such as mining, crushing, and smelting) to separate the valuable components from the gangue (waste material).
Examples
- Minerals: Quartz (SiO₂), Feldspar, Mica.
- Ores: Bauxite (aluminum ore), Hematite (iron ore), Chalcopyrite (copper ore).
Composition
- Minerals: Minerals can consist of a single element or a combination of elements in specific ratios.
- Ores: Ores specifically contain a concentration of metals or valuable minerals, making them suitable for extraction.
This distinction helps clarify the relationship between minerals and ores in the context of geology and mining.
13. Define rusting.
Answer: Rusting is a chemical process in which iron reacts with oxygen and moisture in the environment, leading to the formation of iron oxide, commonly known as rust. This process is an example of corrosion and typically occurs in the presence of water and electrolytes, such as salt. Rusting results in the deterioration of the metal, causing structural weakness and damage over time.
14. Define electrolytic refining.
Answer: Electrolytic refining is a process used to purify metals, such as copper, silver, and gold, through electrolysis. In this method, an impure metal is made the anode in an electrolytic cell, while a pure metal serves as the cathode.
When an electric current is passed through the electrolyte solution, the impure metal oxidizes at the anode, releasing metal ions into the solution. These ions then migrate to the cathode, where they are reduced and deposited as pure metal. This process effectively separates impurities from the desired metal, resulting in a high degree of purity.
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