Chemistry Class 9: Metals and Non-Metals

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Give an example of a metal which is a liquid at room temperature.

Mercury

Give an example of a metal which can be easily cut with a knife.

Sodium

Which metal is the best conductor of heat?

Silver

Give an example of a metal which is a poor conductor of heat.

Lead Signup and view all the answers

Explain the meanings of malleable and ductile.

Malleable means a metal can be beaten into thin sheets, while ductile means a metal can be drawn into wires. Signup and view all the answers

Why is sodium kept immersed in kerosene oil?

To prevent it from reacting with moisture and oxygen in the air. Signup and view all the answers

Which gas is produced when dilute hydrochloric acid is added to a reactive metal?

Hydrogen gas Signup and view all the answers

What would you observe when zinc is added to a solution of iron(II) sulphate?

Zinc will displace iron from the solution, and you will see a change in color indicating a reaction. Signup and view all the answers

Can you write equations for the reactions of calcium and potassium with water?

Calcium: Ca + 2H2O → Ca(OH)2 + H2; Potassium: 2K + 2H2O → 2KOH + H2 Signup and view all the answers

Which metal produces a black oxide when burned in air?

Copper Signup and view all the answers

All metals except mercury exist as solids at room temperature.

True Signup and view all the answers

What are the ions present in Na2O and MgO?

Na+ and O2- for Na2O; Mg2+ and O2- for MgO Signup and view all the answers

Why do ionic compounds have high melting points?

Because a considerable amount of energy is required to break the strong inter-ionic attraction. Signup and view all the answers

Define the term 'Mineral'.

Elements or compounds that occur naturally in the earth's crust. Signup and view all the answers

Define the term 'Ore'.

Minerals that contain a very high percentage of a particular metal and can be profitably extracted. Signup and view all the answers

Define the term 'Gangue'.

Impurities such as soil and sand in ores. Signup and view all the answers

Which of the following metals are found in nature in the free state? (Select all that apply)

Copper Signup and view all the answers

What chemical process is used for obtaining a metal from its oxide?

Reduction Signup and view all the answers

Which metals do not corrode easily?

Gold and platinum. Signup and view all the answers

What are alloys?

Homogeneous mixtures of two or more metals, or a metal and a non-metal. Signup and view all the answers

The rusting of iron can be prevented by _____.

painting, oiling, greasing, galvanising, chrome plating, anodising, or making alloys. Signup and view all the answers

What happens during the rusting of iron?

Iron reacts with moist air to form rust, a brown flaky substance. Signup and view all the answers

State two ways to prevent the rusting of iron.

Applying grease and galvanizing. Signup and view all the answers

Which of the following pairs will give displacement reactions? (Select all that apply)

MgCl2 solution and aluminium metal Signup and view all the answers

Which of the following methods is suitable for preventing an iron frying pan from rusting? (Select all that apply)

Applying grease Signup and view all the answers

Study Notes

Metals and Non-metals

Classification of Elements

Elements are categorized into metals and non-metals based on their properties.
Physical properties are key indicators for classification.

Physical Properties of Metals

Metallic Lustre: Metals have a shiny surface when pure.
Hardness: Metals vary in hardness; most are hard.
Malleability: Metals can be beaten into thin sheets; gold and silver are the most malleable.
Ductility: Metals can be drawn into wires; gold is the most ductile, able to produce a wire of about 2 km from one gram.
Thermal Conductivity: Metals are good heat conductors; silver and copper are the best conductors.
Electrical Conductivity: Metals conduct electricity well; wires are often coated with PVC for safety.
Sonority: Metals produce sound when struck, hence used in bells.

Physical Properties of Non-metals

Non-metals are fewer in number and can be either solid or gas, except bromine which is liquid.
Non-metals generally do not exhibit metallic properties.
Some non-metals (e.g., iodine) can be lustrous.

Reactivity of Metals

Metals react with oxygen to form metal oxides.
Reactivity varies between metals; potassium and sodium react vigorously, while gold and silver resist oxidation.
Protective oxide layers can prevent further reactions (e.g., on magnesium and aluminum).

Reactions of Metals

With Water:
- Certain metals react with cold or hot water, producing hydrogen gas and metal hydroxides.
With Acids:
- Metals react with dilute acids to produce salt and hydrogen gas; magnesium reacts vigorously while copper does not react.
With Metal Salts:
- Some metals can displace other metals from their salt solutions (e.g., copper wire in iron sulfate solution).

Chemical Properties of Metals

Oxide Formation: Reaction of metals with oxygen forms metal oxides; some amphoteric oxides can react with both acids and bases.
General Reaction with Water: Most metals either react with cold or hot water or with steam.
- Example: Sodium and potassium react violently, while metals like aluminum and zinc don’t react with water but can react with steam.
Acid-Base Behavior: Most metal oxides are basic, while non-metal oxides tend to be acidic.

Fun Fact

Aqua Regia: A mixture of hydrochloric and nitric acid, known for dissolving gold and platinum.

Key Observations from Activities

Different metals exhibit different physical and chemical behaviors.
Study the specific reactions and behaviors to understand the overall reactivity and characteristics of metals versus non-metals.

Summary of Key Terms

Malleable: Ability to be shaped into sheets.
Ductile: Ability to be drawn into wires.### Displacement Reactions
Reactive metals can displace less reactive metals from their compounds in solution or molten form.
Displacement reactions provide evidence of metal reactivity: if metal A displaces metal B from solution, A is more reactive than B.
Example of a displacement reaction:
- Metal A + Salt solution of B → Salt solution of A + Metal B

Reactivity Series

The reactivity series ranks metals by their decreasing reactivity.
Developed through displacement experiments.
An example of the reactivity series from most reactive to least reactive:
- Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Lead, Hydrogen, Copper, Mercury, Silver, Gold.

Metal Reactivity Observations

Comparing copper and iron based on their displacement activities reveals which is more reactive.
Findings from displacement reactions help determine the order of reactivity among unknown metal samples A, B, C, and D.

Metal and Water Reactions

Sodium is stored in kerosene to prevent vigorous reactions with moisture in the air.

Chemical Reactions of Metals

Iron reacts with steam in a specific chemical reaction.
Calcium and potassium react with water, producing hydrogen gas.

Gas Production in Metal Reactions

Dilute hydrochloric acid reacting with a reactive metal produces hydrogen gas.
For iron reacting with dilute sulfuric acid, a specific chemical equation outlines the reaction.

Ionic Compounds

Formed by the transfer of electrons from metals (cation formation) to non-metals (anion formation), e.g., sodium to chloride, magnesium to chloride.
Characteristics of ionic compounds:
- Physical Nature: Solid and brittle due to strong ionic bonds.
- Melting and Boiling Points: High values due to strong inter-ionic attraction.
- Solubility: Generally soluble in water, insoluble in non-polar solvents like kerosene.
- Electricity Conductivity: Conduct electricity when dissolved in water or in molten state; do not conduct in solid form.

Extraction of Metals

Metals occur mainly in mineral forms in the Earth's crust.
Ores are minerals with a high concentration of specific metals and can be profitably extracted.

Categories of Metal Reactivity

Low Reactivity: Metals can often be found in their free state (e.g., gold, silver).
Moderate Reactivity: Typically found as oxides, sulphides, or carbonates.
High Reactivity: Always found in compounds due to their reactivity.

Steps in Metal Extraction

Enrichment: Process of removing impurities (gangue) from ores before extraction.
Metals low in the activity series are reduced through heating, e.g., mercuric oxide to mercury.
Metals in the middle of the series can be obtained by roasting or calcination, converting sulphide or carbonate ores to oxides.
For higher reactivity metals, displacing lower reactivity metals or using electrolysis may be necessary for extraction.

Thermit Reaction

A highly exothermic reaction used to produce molten metals, e.g., iron from iron(III) oxide using aluminium as a reducing agent; significant heat generation, making it practical for joining metals like railways.### Electrolytic Reduction of Metals
Metals with higher affinity for oxygen than carbon require electrolytic reduction for extraction.
Sodium, magnesium, and calcium are extracted via electrolysis of molten chlorides.
Key reactions in electrolysis include:
- At cathode: Na⁺ + e⁻ → Na
- At anode: 2Cl⁻ → Cl₂ + 2e⁻
Aluminium is also extracted through the electrolysis of aluminium oxide.

Refining of Metals

Raw metals produced from reduction processes are often impure and must be refined.
Electrolytic refining is a common method for purifying metals like copper, zinc, tin, nickel, silver, and gold.
The process involves:
- Impure metal as the anode and pure metal strip as the cathode.
- Electrolyte typically contains metal salt (e.g., acidified copper sulfate).
- Current causes pure metal to deposit on the cathode while impurities dissolve or settle.

Corrosion of Metals

Corrosion occurs when metals like silver, copper, and iron react with environmental factors:
- Silver tarnishes due to silver sulfide formation.
- Copper develops a green patina of copper carbonate.
- Iron rusts when exposed to moisture, forming flaky brown rust.

Conditions Leading to Iron Rusting

An experiment with three test tubes demonstrates rusting mechanics:
- Test Tube A (water and air) leads to rust.
- Test Tube B (boiled, oil-covered water) prevents rust.
- Test Tube C (dry air) also prevents rust.
Rusting requires both moisture and air.

Prevention of Corrosion

Methods to prevent rusting include:
- Painting, oiling, greasing, galvanizing, chrome plating, anodizing, and alloying.
Galvanization involves coating steel and iron with zinc for protection.
Alloying alters metal properties; e.g., iron mixed with carbon becomes harder.
Stainless steel forms by combining iron with nickel and chromium, providing rust resistance.

Properties and Classification of Metals

Metals are typically lustrous, malleable, ductile, and good conductors of heat and electricity, solid at room temperature (except mercury).
Metals can lose electrons to form positive ions with non-metals.
Common metals exist as free elements or in compounds.

Alloys and Their Characteristics

Alloys are homogeneous mixtures of two or more metals, or metals with non-metals.
Created by melting metals and dissolving other components in defined proportions.
Different properties of alloys, such as reduced electrical conductivity and melting points, are critical in engineering and manufacturing.

Unique Metallurgical Facts

The iron pillar near Qutub Minar in Delhi demonstrates ancient Indian metallurgy, indicating rust resistance.
This pillar, 8 m tall and weighing 6 tonnes, showcases remarkable historical metalworking techniques.

Reactivity and Displacement Reactions

Reactivity series categorizes metals based on their reactions with water and dilute acids.
Metals above hydrogen in the activity series can displace hydrogen from acids, and more reactive metals displace less reactive metals from solutions.

Non-Metals versus Metals

Non-metals are typically brittle, poor conductors, and can form negatively charged ions.
They react with metals to form hydrides and can create either acidic or neutral oxides.

Summary Points on Corrosion

Corrosion is the gradual destruction of metals via environmental exposure.
Effective prevention strategies include physical barriers (like coatings) and employing alloys with better durability.
Notable alloys such as brass and bronze possess distinct characteristics not found in pure metals, emphasizing their importance in practical applications.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the classifications and properties of metals and non-metals as covered in Chapter 3 of Class IX Chemistry. Reflect on everyday uses of these elements and understand how their properties influence their applications in real life. Test your knowledge of key concepts and properties that distinguish metals from non-metals.