The World of Metals and Non-metals

Physical Properties of Metals

The World of Metals and Non-metals: An Introduction

Have you ever wondered why a school bell is made of metal, but your pencil's lead is not? Or why electrical wires are made of shiny copper, but the coating around them is a type of dull plastic? The world is full of different materials, each chosen for a specific job because of its unique characteristics.

In this chapter, we will become material detectives! We will explore the two major families of elements that make up almost everything around us: metals and non-metals. By the end, you'll be able to look at an object and make a smart guess about what it's made of and why.

{{VISUAL: photo: A vibrant collage showing diverse examples of metals (shiny gold coins, a steel spoon, copper wire) and non-metals (a lump of yellow sulfur, black charcoal, a plastic water bottle).}}

What Will We Discover?

Get ready to uncover the secrets of these amazing materials. We will learn:

• The special physical properties that make metals shiny and strong.
• How non-metals are different in their look, feel, and behaviour.
• The chemical reactions that change metals and non-metals into new substances.
• Where we find and use these elements in our daily lives, from kitchens to rockets!

Our investigation begins by looking at their most obvious features, known as physical properties. These are the clues we can observe using our senses—like how something looks, if it's hard or soft, and whether it can be bent or stretched without breaking. These clues help us sort elements into the correct family.

{{VISUAL: diagram: A simple illustration showing two key properties of metals. On the left, a hammer is flattening a metal block into a thin sheet (labeled Malleability). On the right, a metal block is being stretched into a long, thin wire (labeled Ductility).}}

Now, let's dive into our first mission: uncovering the physical properties that define a metal.

Physical Properties of Non-metals

The World of Metals and Non-metals

Page 2 of 5: Physical Properties of Non-metals

On the last page, we met the shiny, strong, and musical members of the element family: the metals. Now, let's turn our attention to their counterparts: the non-metals. If metals are like the strong frame of a building, non-metals are like the air inside, the glass in the windows, and the water in the pipes—often less obvious, but absolutely essential for life and function!

Non-metals have a set of physical properties that are, in many ways, the opposite of metals. Let's explore them one by one.

1. Physical State: Solids, Liquids, and Gases!

Unlike metals, which are almost all solids at room temperature (except mercury), non-metals are much more diverse. They are the only group of elements that exist in all three states of matter under normal conditions.

• Solids: Many non-metals are solids. Think of carbon (in the form of coal or the graphite in your pencil) and the yellow, powdery sulfur.
• Liquid: There is only one non-metal that is a liquid at room temperature: bromine. It's a reddish-brown liquid that is very reactive.
• Gases: A large number of non-metals are gases. The air we breathe is a mixture of non-metallic gases like nitrogen (about 78%), oxygen (about 21%), and others. Hydrogen and chlorine are also gases.

{{VISUAL: photo: A comparison of three non-metals in their natural state at room temperature: a piece of yellow solid sulfur, a sealed vial of reddish-brown liquid bromine, and a transparent container showing the faint greenish-yellow gas chlorine.}}

2. Appearance and Hardness: Dull and Brittle

How do non-metals look and feel? Mostly, they are the complete opposite of the strong, shiny metals.

Lack of Lustre

Non-metals are generally non-lustrous, meaning they do not have a shiny surface. They usually appear dull. Compare a piece of coal (carbon) to a steel spoon. The difference is clear!

• Interesting Exceptions: Iodine crystals have a faint, dark lustre. Also, graphite, a form of carbon, is somewhat shiny.

Softness and Brittleness

Most non-metals are quite soft. Sulfur powder can be crushed easily, and graphite leaves a mark on paper because it's soft enough to rub off.

• The Ultimate Exception: Diamond, which is also a form of carbon, is the hardest natural substance known on Earth! It can easily scratch any metal.

Instead of being strong, solid non-metals have a property called brittleness. This means they are likely to break, shatter, or crumble when hit with a force. They cannot be bent or stretched.

{{KEY: type=definition | title=Brittleness | text=Brittleness is the property of a material that causes it to fracture or shatter when subjected to stress or impact, without significant bending or deformation.}}

Imagine hitting a lump of coal with a hammer. It won't flatten into a sheet; it will break into smaller pieces. This property is a key identifier for solid non-metals.

{{VISUAL: diagram: A simple two-panel diagram. Panel 1 shows a hammer hitting a metallic block, which flattens (labeled 'Malleable'). Panel 2 shows a hammer hitting a block of sulfur, which shatters into small pieces (labeled 'Brittle').}}

3. Malleability and Ductility: Not at All!

Do you remember how metals are malleable (can be beaten into thin sheets) and ductile (can be drawn into wires)?

Because non-metals are brittle, they are non-malleable and non-ductile.

• You cannot hammer a piece of solid sulfur into a thin sheet. It will simply shatter.
• You cannot pull carbon into a long, thin wire. It will snap.

This lack of malleability and ductility is one of the most reliable differences between metals and solid non-metals.

4. Sonority: No Ringing Sound

When you strike a metal bell, it produces a clear, ringing sound. This property is called sonority. Non-metals, on the other hand, are non-sonorous.

If you tap a block of wood (made mostly of carbon), it produces a dull thud, not a ringing sound. Non-metals do not vibrate in the same way as metals to produce that characteristic musical sound.

{{ZOOM: title=Allotropes of Carbon: Diamond vs. Graphite | text=Why are diamond and graphite so different, even though both are just carbon? It's due to how their atoms are arranged. In diamond, atoms are locked in a strong, rigid 3D structure, making it super hard. In graphite, atoms are in flat layers that can slide past each other, making it soft and a good conductor of electricity.}}

5. Conductivity: Excellent Insulators

Conductivity is the ability of a material to allow heat or electricity to pass through it.

Thermal Conductivity

Non-metals are generally poor conductors of heat. This is why materials like wood, plastic, and wool are used to keep things warm or to handle hot objects. The handle of a cooking pan is made of plastic (a substance rich in non-metals like carbon and hydrogen) so that heat from the pan doesn't reach your hand.

Electrical Conductivity

Similarly, non-metals are poor conductors of electricity. They act as insulators, which are materials that block the flow of electric current. This is a vital safety feature! The rubber and plastic coating around electrical wires prevents us from getting an electric shock.

{{KEY: type=exam | title=The Critical Exception | text=In exams, you will almost always be asked about the exception to conductivity in non-metals. Remember: Graphite, a form of carbon, is a good conductor of electricity. This is why it is used to make electrodes in batteries and electric cells.}}

By understanding these properties, we can easily distinguish a non-metal from a metal. Let's summarize what we've learned.

{{KEY: type=points | title=Key Physical Properties of Non-Metals | text=- Exist in all three states: solid, liquid, or gas.

• Are generally dull and non-lustrous (exceptions: iodine, graphite).
• Are soft (exception: diamond) and brittle (break easily).
• Are non-malleable and non-ductile.
• Are non-sonorous (do not make a ringing sound).
• Are poor conductors of heat and electricity (exception: graphite).}}

Non-metals might not be shiny or strong, but their properties as insulators and their diverse forms make them fundamental to life and technology, from the air we breathe to the pencil we write with.

Chemical Properties of Metals

{{FORMULA: expr=Metal + Dilute Acid → Salt + Hydrogen Gas | symbols=→:yields or produces}}

The Chemical Personality of Metals

We've seen that metals can be shiny, hard, and great conductors. But what happens when they get into a chemical "conversation" with other substances? Their true personality—their chemical properties—comes out. Unlike physical properties, which you can observe without changing the substance itself, chemical properties describe how a substance reacts and transforms into something new.

Let's dive into the most common reactions that reveal the chemical nature of metals.

1. Reaction with Oxygen: The Story of Tarnish and Rust

Have you ever noticed how a shiny iron nail left outside develops a reddish-brown, flaky coating? Or how a silver anklet loses its shine over time? This is a chemical reaction with oxygen from the air.

When a metal reacts with oxygen, it forms a new compound called a metallic oxide. This process is also known as oxidation.

The general reaction is: Metal + Oxygen → Metallic Oxide

• Iron (Fe): When iron is exposed to oxygen and moisture (water), it rusts. Rust is simply hydrated iron oxide. Iron + Oxygen + Water → Iron Oxide (Rust)

• Magnesium (Mg): If you've ever seen a science demonstration, you might have seen a magnesium ribbon being burnt. It burns with a dazzling white light, leaving behind a white, powdery ash. This ash is magnesium oxide. Magnesium + Oxygen → Magnesium Oxide

{{VISUAL: photo: A pair of tongs holding a burning magnesium ribbon over a watch glass, showing a brilliant white flame and a white powder collecting below.}}

Are Metallic Oxides Acidic or Basic?

This is a crucial question! Let's find out with a simple activity.

1. Take the magnesium oxide powder formed from burning the ribbon.
2. Dissolve a small amount of it in water. It forms a new substance called magnesium hydroxide. Magnesium Oxide + Water → Magnesium Hydroxide
3. Now, dip a strip of red litmus paper and a strip of blue litmus paper into this solution.
4. You will observe that the red litmus paper turns blue, while the blue litmus paper shows no change.

This simple test proves that magnesium oxide is basic in nature.

{{KEY: definition | title=Metallic Oxides | text=Compounds formed when metals react with oxygen. Most metallic oxides are basic in nature, meaning they form a base when dissolved in water.}}

{{KEY: points | title=Testing the Nature of Metallic Oxides | text=- Metallic oxides dissolve in water to form metal hydroxides.

• Metal hydroxides are bases.
• Bases turn red litmus paper blue.
• Therefore, most metallic oxides are basic.}}

2. Reaction with Water: From a Gentle Fizz to a Violent Bang

Not all metals react with water in the same way. Their reactivity determines the speed and conditions of the reaction.

Highly Reactive Metals: Metals like sodium (Na) and potassium (K) are so reactive that they react explosively even with cold water! They zip around the surface of the water, producing a hissing sound and releasing hydrogen gas. The reaction produces so much heat that the hydrogen gas often catches fire. Sodium + Water → Sodium Hydroxide + Hydrogen

Safety First! Reactions with sodium and potassium are extremely dangerous and should only be performed by a teacher in a controlled environment.

Moderately Reactive Metals: Metals like magnesium (Mg) won't do much in cold water, but they react with hot water to form magnesium hydroxide and hydrogen gas. Iron (Fe) is even less reactive; it only reacts with steam (gaseous water) at high temperatures.

Least Reactive Metals: Metals like copper (Cu), silver (Ag), and gold (Au) do not react with water or steam at all. This is why they are used to make pipes, jewellery, and coins—we don't want them to corrode away!

3. Reaction with Acids: The Hydrogen Pop Test

One of the defining characteristics of most metals is their reaction with dilute acids like hydrochloric acid (HCl) and sulfuric acid (H₂SO₄).

When a metal reacts with a dilute acid, it typically produces a salt and hydrogen gas.

The general reaction is: Metal + Dilute Acid → Salt + Hydrogen Gas

For example, if you drop a few granules of zinc (Zn) into a test tube containing dilute hydrochloric acid, you will immediately see bubbles fizzing out. These bubbles are hydrogen gas. Zinc + Hydrochloric Acid → Zinc Chloride (a salt) + Hydrogen

{{VISUAL: diagram: A labeled diagram showing a test tube with zinc granules and dilute hydrochloric acid. A delivery tube is shown carrying the evolved gas to a soap solution, with a burning splinter being brought near a soap bubble, which bursts with a 'pop' sound.}}

{{ZOOM: title=The "Pop" Sound Test | text=How do we know the gas is hydrogen? If you bring a burning matchstick or splinter near the mouth of the test tube, the gas will burn with a characteristic 'pop' sound. This is the definitive test for the presence of hydrogen gas in a school laboratory.}}

Again, reactivity matters. A more reactive metal like magnesium will fizz much more vigorously with acid than zinc. A very unreactive metal like copper will not react with dilute acids at all.

{{KEY: concept | title=Reaction of Metals with Acids | text=Most metals react with dilute acids to displace hydrogen and form a metal salt along with hydrogen gas. The vigour of the reaction depends on the metal's position in the reactivity series. The evolved hydrogen gas can be identified by the 'pop' sound test.}}

4. Reaction with Bases

This is a bit more selective. While most metals react with acids, only a few react with bases like sodium hydroxide (NaOH). Metals like aluminium (Al) and zinc (Zn) are special because they can react with both acids and bases.

When they react with a base, they also produce hydrogen gas. Aluminium + Sodium Hydroxide + Water → Sodium Aluminate + Hydrogen

This special property of reacting with both acids and bases is something you will explore more in higher classes. For now, it's good to know that this reaction is also possible for some metals.

Chemical Properties of Non-metals

{{FORMULA: expr=Non-metal + Oxygen → Non-metallic Oxide | symbols=O₂:Oxygen, CO₂:Carbon dioxide, SO₂:Sulphur dioxide}}

Chemical Properties of Non-metals

On the previous page, we saw how metals behave in chemical reactions—forming positive ions, reacting with acids to produce hydrogen gas, and creating basic oxides. Now, let's switch gears and explore the fascinating and often opposite chemical world of non-metals!

Non-metals, like carbon, sulphur, and oxygen, have a completely different chemical personality. Instead of giving away electrons, they love to gain or share them. This fundamental difference leads to a unique set of reactions.

1. Reaction with Oxygen

What happens when you burn a piece of charcoal (which is mostly carbon) or a matchstick (which has sulphur in its head)? Both combine with oxygen from the air. This is the most common reaction for non-metals.

When a non-metal reacts with oxygen, it forms a non-metallic oxide.

• Carbon: When carbon burns in a sufficient supply of air, it forms carbon dioxide. C + O₂ → CO₂ (Carbon dioxide)

• Sulphur: When sulphur powder is heated, it burns with a blue flame to form sulphur dioxide. S + O₂ → SO₂ (Sulphur dioxide)

But what is the nature of these oxides? Are they like the basic oxides that metals form? Let's find out.

The Nature of Non-metallic Oxides

If you take the gas produced from burning sulphur (sulphur dioxide) and dissolve it in water, it forms a new substance called sulphurous acid.

SO₂ + H₂O → H₂SO₃ (Sulphurous acid)

Similarly, if you dissolve carbon dioxide in water (which happens in fizzy drinks!), you get carbonic acid.

CO₂ + H₂O → H₂CO₃ (Carbonic acid)

As their names suggest, these substances are acids. An acid is a substance that will turn blue litmus paper red. This simple test proves a very important property.

{{KEY: type=definition | title=Acidic Oxides | text=Non-metallic oxides that react with water to form acids are called acidic oxides. They turn blue litmus paper red when dissolved in water.}}

{{VISUAL: diagram: A two-part diagram. Part A shows sulphur powder being heated in a deflagrating spoon inside a gas jar, producing sulphur dioxide gas. Part B shows water being added to the jar, shaken, and a strip of moist blue litmus paper being dipped into the solution, turning red.}}

This acidic nature is a key difference from metals, which form basic oxides that turn red litmus paper blue.

{{ZOOM: title=The Science Behind Acid Rain | text=The acidic nature of non-metal oxides has a huge environmental impact. Sulphur dioxide (from factories) and nitrogen oxides (from vehicle exhaust) rise into the atmosphere, dissolve in water droplets in clouds, and fall back to Earth as acid rain. This damages monuments like the Taj Mahal, harms aquatic life, and affects soil quality.}}

2. Reaction with Water

Do you think a piece of coal dissolves or fizzes when you drop it in water? Not at all!

This observation holds true for most non-metals. Non-metals generally do not react with water.

This is because, unlike reactive metals, non-metals cannot give electrons to the hydrogen in water to release hydrogen gas. There is no chemical reaction. In fact, some very reactive non-metals, like white phosphorus, are actually stored under water to prevent them from reacting explosively with the oxygen in the air!

3. Reaction with Acids

Just as they don't react with water, non-metals generally do not react with dilute acids either.

Let's recall why a metal like zinc reacts with hydrochloric acid (HCl). Zinc is able to push the hydrogen out of the acid and take its place, releasing hydrogen gas (H₂). To do this, it has to give electrons to the hydrogen ions (H⁺).

Non-metals are electron takers, not electron givers. They cannot displace hydrogen from acids. If you place a piece of charcoal in a test tube with dilute hydrochloric acid, you will observe no bubbles and no reaction.

{{KEY: type=concept | title=Why No Reaction with Water or Acids? | text=Non-metals are electron acceptors. To react with water or acids, an element must donate electrons to displace hydrogen ions (H⁺) and form hydrogen gas (H₂). Since non-metals tend to gain or share electrons rather than donate them, they cannot displace hydrogen, and thus no reaction occurs.}}

{{VISUAL: chart: A simple comparison table with two columns. Column 1 (Metal) shows a drawing of zinc granules in a test tube with dilute acid, with bubbles of H₂ gas rising. Column 2 (Non-metal) shows charcoal powder in a test tube with dilute acid, with no bubbles or change.}}

4. Reaction with Bases

While the direct reaction of non-metals with bases can be complex, the reaction of their oxides is very straightforward and important.

Since we know non-metallic oxides are acidic in nature, what do you think happens when an acid meets a base? They neutralise each other!

An acidic oxide (from a non-metal) will react with a base to form a salt and water.

For example, carbon dioxide (CO₂) reacts with sodium hydroxide (NaOH), a strong base, to form sodium carbonate (a salt) and water.

CO₂ + 2NaOH → Na₂CO₃ + H₂O

{{KEY: type=exam | title=Testing for Carbon Dioxide | text=This reaction is the basis for the classic 'limewater test'. Limewater is a base (calcium hydroxide). When you bubble carbon dioxide through it, it turns milky due to the formation of a white, insoluble salt called calcium carbonate.}}

The chemical story of a non-metal is one of accepting or sharing, leading to the formation of acidic compounds that shape our world, from the fizz in our drinks to the rain from the sky.

Uses of Metals and Non-metals & Exercises

Uses of Metals and Non-metals

We've explored the fascinating properties that separate metals from non-metals. But why does it matter? Because these very properties—strength, conductivity, brittleness, reactivity—determine how we use these elements to build our world. From the giant bridges we cross to the air we breathe, metals and non-metals are everywhere, performing essential jobs.

Everyday Uses of Common Metals

The unique physical properties of metals make them incredibly versatile. Let's look at some key examples you see and use daily.

• Iron (Fe): Known for its immense strength and low cost, iron is the backbone of modern infrastructure. It's used to make bridges, buildings, railway tracks, vehicles, and heavy machinery. Often, it is mixed with carbon to create an alloy called steel, which is even stronger.

• Copper (Cu): If you could see inside the walls of your house, you would find copper. Its excellent electrical conductivity makes it the top choice for electrical wires. It is also a good conductor of heat, which is why it's often used for the base of high-quality cooking pans and in car radiators.

• Aluminium (Al): This metal is special because it is both strong and lightweight. This combination makes it perfect for building aircraft, high-performance cars, and even window frames. Its high malleability allows it to be rolled into very thin sheets, which you know as aluminium foil for packing food. It also doesn't rust easily, making it great for drink cans and utensils.

{{VISUAL: photo: a collage showing common uses of metals like an iron bridge, copper wires, aluminium foil, and gold jewelry.}}

• Gold (Au) & Silver (Ag): Why are these metals used for jewelry? Because of their brilliant lustre (shininess) and the fact that they are highly unreactive. They don't easily corrode or tarnish, so they maintain their beauty for a long time. Their ductility and malleability also make them easy to shape into intricate designs.

{{KEY: type=points | title=Why Metals are Widely Used | text=- High strength for construction (Iron).

• Excellent electrical conductivity for wiring (Copper, Aluminium).
• Malleability for making thin sheets and foils (Aluminium).
• Ductility for drawing into wires (Copper).
• Lustre and non-reactivity for jewelry (Gold, Silver).}}

Essential Uses of Common Non-metals

Non-metals might not be as shiny or strong as metals, but they are just as crucial—in many cases, even more so for life itself!

• Oxygen (O): This one is simple: oxygen is essential for respiration. All living beings, including us, need oxygen to survive. It is also necessary for any form of combustion (burning).

• Nitrogen (N): While we don't breathe it in for energy, nitrogen is a vital component of proteins and DNA. Its most important use is in making fertilizers (like urea), which help plants grow and are fundamental to agriculture.

• Carbon (C): Carbon is the element of life! It is the basic building block of all living things. In its pure form, it has two famous avatars:

  • Diamond: The hardest known natural substance, used in cutting tools and jewelry.
  • Graphite: A soft, slippery solid that conducts electricity. It's used to make pencil 'lead' and electrodes in batteries.

• Sulphur (S): This yellow, brittle solid is used in the manufacturing of matches, fireworks, and gunpowder. It is also used to make sulphuric acid, a very important industrial chemical.

• Iodine (I): You might have seen a purple-coloured solution being applied to a cut or wound. That is tincture of iodine, an antiseptic that kills germs.

{{VISUAL: chart: a mind map illustrating the various uses of common non-metals like oxygen for breathing, nitrogen in fertilizers, carbon as diamond and graphite, and sulfur in matches.}}

A Special Case: Alloys

Sometimes, a pure metal doesn't have the perfect set of properties for a specific job. For instance, pure iron rusts easily, and pure gold is very soft. To fix this, we create alloys.

{{KEY: type=definition | title=Alloy | text=An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal, created to enhance properties like strength, hardness, or resistance to corrosion.}}

By mixing elements, we can create materials with superior qualities.

{{ZOOM: title=The Problem of Rusting | text=Iron is incredibly strong, but it has a major weakness: it rusts (corrodes) when exposed to oxygen and moisture. This is a chemical reaction that forms iron oxide, a flaky brown substance. Alloying iron with chromium and nickel to make stainless steel prevents this rusting, making it perfect for kitchen utensils and surgical instruments.}}

Chapter Exercises

Time to test your knowledge! Try to answer these questions based on what you've learned in the entire chapter.

A. Objective Type Questions

1. Fill in the blanks: a. The property of metals by which they can be beaten into thin sheets is called __________. b. The only metal which is liquid at room temperature is __________. c. Non-metals are generally __________ conductors of heat and electricity. d. The alloy of copper and zinc is known as __________.

2. Multiple Choice Questions (MCQs): i. Which of the following non-metals is lustrous? (a) Sulphur (b) Carbon (c) Iodine (d) Oxygen

   ii. When a metal reacts with an acid, which gas is generally produced? (a) Oxygen (b) Hydrogen (c) Carbon dioxide (d) Nitrogen

B. Short Answer Questions

3. Give reasons for the following: a. Electric wires are made of copper. b. Immersion rods for heating liquids are made of metallic substances. c. Aluminium foil is used to wrap food items.

4. Write two differences between metals and non-metals on the basis of their physical properties.

5. What happens when a copper vessel is exposed to moist air for a long time? Write the equation for the reaction.

{{KEY: type=exam | title=Reasoning Questions | text=Questions often ask 'Why is X used for Y?'. Your answer must connect a specific property (e.g., conductivity) to the specific use (e.g., making electrical wires). Just stating the use is not enough.}}

C. Higher Order Thinking Skills (HOTS)

6. Ria's mother stores lemon pickle in a glass jar. She advises Ria never to store it in a copper or aluminium container. Why do you think she gives this advice? (Hint: Think about the chemical nature of lemon pickle and metals).

7. A bell in a temple is made of metal, not wood. Can you explain why, based on the properties you have learned?