The World Of Metals And Non-Metals

Hello my dear students, welcome to today's science lesson. I'm so happy to see you all here, ready to learn something new and exciting. Today, we are going to explore a chapter that is very close to our everyday life, something that we use and see around us every single day. We are going to learn about Chapter 4: The World of Metals and Non-metals.

Now, before we begin, let me ask you something. Have you ever seen an ironsmith working in your village? Perhaps some of you have seen someone making utensils or tools from iron. In our chapter, we meet two students named Yashwant and Anandi who live in a village in Rajasthan. They were given a school project to learn about craftspersons who work with metals. So, they decided to visit the local ironsmiths. They went with their grandfather to meet an elderly craftsperson named Sudarshan uncle.

Now, isn't it wonderful that even today, in many parts of our India, we have skilled artisans who work with metals? Sudarshan uncle told them that he makes items of daily use like flat pans which we call tawas, buckets or baltis, tongs or chimtas, and farming tools like spades which are called phawras, axes or kulhadis, trowels or khurpis, and rakes or jelees. All these are made from iron metal, and wherever needed, they use wood for handles. They also use coal in their furnaces to heat the iron.

Now, here comes the interesting part. Sudarshan uncle was heating an iron block in his furnace, and it became red hot. Then he started beating it hard with a hammer. Anandi was amazed and asked, "Why are you beating it?" And Sudarshan uncle said, "I am beating it to shape it into an axe." Can you imagine that? A piece of iron can be beaten into a flat shape! Anandi was so surprised that she asked, "Can we do this with other metals as well?"

This is exactly what we are going to find out in this chapter. We will explore what metals are, what properties they have, how they are different from non-metals, and why they are so useful to us. So, let's begin our journey into the world of metals and non-metals.

Now, let's start with Section 4.1: Properties of Materials. We are going to learn about some very important properties that help us distinguish between metals and non-metals.

The first property we are going to learn about is called Malleability. Now, what does that word mean? Let me explain. Remember when Sudarshan uncle was beating the iron to shape it into an axe? That ability to be beaten into thin sheets is what we call malleability. The property by which materials can be beaten into thin sheets is called malleability.

Now, let's do an activity to understand this better. This is Activity 4.1 from your textbook. But remember, always conduct this activity under the supervision of your teacher or an adult because we are using a hammer.

First, collect some waste pieces of copper and aluminium, an iron nail, a piece of coal, a pea-sized lump of sulfur, which we also call gandhak, and a block of wood. Now, look at each of these items carefully. Are they lustrous? That means do they have a shiny appearance? Also, note whether they are hard or soft. Record your observations in a table like Table 4.1 given in your textbook.

Now, here comes the important part. Place each of these items one by one on any hard surface and beat them with a hammer. What do you think will happen? Do the objects become slightly flattened, or do they break into pieces? Record your observations in the table.

Let me tell you what we would observe. When we beat copper, aluminium, and iron, they become flat. They don't break into pieces. They can be hammered into thin sheets. This is malleability. But when we beat coal or sulfur, they break into pieces. They are brittle. And wood neither gets flattened into a sheet nor breaks into pieces in the same way. Wood is neither malleable nor brittle.

So, my dear students, let me tell you what we learned from this activity. Objects made from copper, aluminium, and iron are lustrous, meaning they have a shiny appearance. This shine is called metallic lustre. Materials like copper, aluminium, and iron are known as metals, whereas coal, sulfur, and wood are non-lustrous and not as hard as metals.

Now, here is an important question. Are all metals hard and solid? Not really! Some metals like sodium and potassium are so soft that they can be cut with a knife. And there is one metal, mercury, that is found in a liquid state at room temperature. You might have seen mercury in thermometers. That's why mercury is special among metals.

Now, coming back to malleability, most metals possess this property. Can you give some examples of metal sheets? You might have seen thin silver foil on some sweets and aluminium foil used for wrapping food items. These are formed due to their malleability. Gold and silver are the most malleable metals. That means they can be beaten into the thinnest sheets. Isn't that wonderful?

On the other hand, a piece of coal or a lump of sulfur does not show this behaviour. They break into pieces and are said to be brittle. So, remember, malleable means can be beaten into thin sheets, while brittle means breaks into pieces when beaten.

Now, before we move to the next property, let me quickly recap what we learned. We learned that metals are generally lustrous, meaning they have a shiny appearance called metallic lustre. We also learned about malleability, which is the ability of a material to be beaten into thin sheets. Metals like gold, silver, copper, aluminium, and iron are malleable. Non-metals like sulfur and coal are brittle, meaning they break into pieces when beaten.

Now, let's move to the next property, which is called Ductility. Where do you find the use of metal wires? You might have seen wires of metals like copper or aluminium in electrical fittings in your homes. Some ornaments, like bangles, necklaces, and earrings, are also made from metal wires. Metal wires also play important functions in a variety of stringed musical instruments, such as veena, sitar, violin, and guitar.

This property of materials by which they can be drawn into wires is called ductility. This property of ductility is mainly possessed by metals. Gold is so ductile that one gram of it can be drawn into a 2 kilometre-long wire! Can you imagine that? Just one gram of gold can be stretched into a wire that is 2 kilometres long! That is absolutely amazing.

Now, have you ever seen wires made of coal or sulfur? Obviously not! We can say that coal and sulfur are not ductile. They cannot be drawn into wires.

Do you know that ropes made of steel wires can support heavy loads? Steel is a mixture of metal, which is iron, and non-metal, which is carbon. Therefore, steel wires are used in suspension bridges and in cranes to lift heavy objects. This is because of the ductile nature of metals.

So, to recap, ductility is the property by which materials can be drawn into wires. Metals like gold, silver, copper, aluminium, and iron are ductile. Non-metals are not ductile.

Now, let's learn about another interesting property called Sonority. Have you ever noticed the sound produced when a metal spoon, or a metal plate, or a metal coin is dropped on the floor? How is it different from the sound produced when a piece of coal or wood is dropped on the floor?

Let's do an activity to understand this better. This is Activity 4.2. But remember, be careful while dropping the objects.

Take a few objects, such as a metal spoon, a coin, a piece of coal, and a block of wood. Drop them one by one from a certain height. Do you notice any difference in the sound produced by these objects?

You would observe that the metal spoon and the metal coin produce a ringing sound. Coal and wood, on the other hand, produce dull sounds.

This property of metals that enables them to produce a ringing sound is called sonority, and metals are said to be sonorous in nature. The ringing sound of ghungroos, which are those small bells tied to the ankles of dancers, is due to the sonority of metals. The ringing sound of the school bell is also due to the sonority of metals. Even some people who are blind use the difference in sound when their stick hits wood or metal to help find their way.

So, to recap, sonority is the property of metals to produce a ringing sound when struck. Metals are sonorous, while non-metals like coal and wood are not sonorous.

Now, let's learn about the next property, which is about heat. This is called Conduction of Heat. Have you ever observed the vessels used for cooking in the kitchen? You might have noticed that the vessels used for heating are made of metals. Can you name some metals that are used for making cooking vessels? That's right, we use stainless steel, aluminium, and copper for making cooking vessels. Do you know why these metals are used for this purpose? Let's find out!

Let's do Activity 4.3. Remember, this activity must be performed under the supervision of your teacher or an adult. Be careful while handling hot water.

Place a glass tumbler on a table. Fill it with hot water. Take a metal spoon and a wooden spoon of almost the same size and thickness. Immerse both the spoons simultaneously into the hot water and leave them undisturbed for a few minutes. Now, carefully touch the upper end of each spoon. Which of the spoons get hotter?

You may have noticed that the metal spoon is hotter to touch than the wooden spoon. Even though both spoons are immersed in the water of the same temperature and for the same time. This shows that the heat transfers through the metal spoon, making it hotter. In contrast, the wooden spoon transfers heat poorly.

In such cases, the transfer of heat from one point to another of a material is called conduction, and materials that transfer heat are called conductors. Based on the observations, one can say that metals are good conductors of heat, whereas wood is a poor conductor of heat.

Now, we can understand why mostly metal vessels are used for cooking, and their handles are made with wood or other materials that do not conduct heat. This prevents the heat from traveling up to our hands when we hold the vessel. You will learn more about this in the chapter 'Heat Transfer in Nature'.

So, to recap, conduction is the transfer of heat from one point to another of a material. Metals are good conductors of heat, while materials like wood are poor conductors of heat.

Now, let's learn about the conduction of electricity, which is Section 4.1.5. Have you ever seen an electrician using a screwdriver? What type of material is used for making its handle? You may have also noticed the electrician wearing rubber gloves and shoes while working. What can be the reason for this?

Let's do an activity to understand this better. This is Activity 4.4. We need to design an electric circuit, like the tester circuit you learned about in the chapter 'Electricity: Circuits and their Components'.

Collect a few objects, such as a piece of aluminium foil, an iron nail, a lump of sulfur, a copper wire, a piece of coal, a piece of dry wood, a stone, an eraser made of rubber, and a piece of nylon rope. Now, predict which of these could make the bulb of the tester glow and which could not. Then, test each object and record your observations in a table like Table 4.2.

You might have observed that objects made of aluminium, iron, and copper make the bulb glow, whereas sulfur, coal, wood, stone, eraser, and nylon rope could not make it glow. Do you see any pattern in the glowing of bulbs when using different materials? It is observed that all the materials that make the bulb glow are metals.

Materials that allow electricity to flow through them easily are called good conductors of electricity. In contrast, materials that prevent the bulb from glowing by not allowing electricity to pass through them are called poor conductors of electricity.

So, now we can understand that the plastic covering on screwdrivers and rubber gloves protect the electrician from electric shock because these materials are poor conductors of electricity.

So, to recap, metals are good conductors of electricity, while non-metals and other materials like plastic, rubber, wood, and coal are poor conductors of electricity.

Now, let's summarize what we have learned so far. We learnt that metals are generally hard, lustrous, malleable, ductile, and good conductors of heat and electricity. Now, let us learn how metals behave in the presence of air and water. This is Section 4.2.

You would have often noticed that iron objects develop brown deposits when left in the open for a few days. In which conditions would an iron object develop brown deposits? Is it when it comes into contact with dry air only, or water only, or both air and water? Let's do an activity to find out.

This is Activity 4.5. Caution: Be careful while handling iron nails.

Take a few shining iron nails. If you are using old iron nails, make sure to remove brown deposits from their surface by scrubbing them with the help of a small piece of sandpaper.

Take three clean, dry glass bottles or test tubes with tight-fitting caps or stoppers. Label them A, B, and C.

Take three iron nails and tie each iron nail with a thread.

Now, for bottle A: Place one iron nail and some silica gel in the glass bottle and tighten the cap or stopper. Silica gel makes the air dry. It is the substance that is used in small pouches in some medicine bottles, water bottles, shoe boxes, and so on, to keep them dry.

For bottle B: Place one iron nail in the glass bottle. Pour freshly boiled and cooled water into it until the iron nail is completely dipped in it. Now, pour some oil to form a layer over the surface of the water. The layer of oil on the surface of the water prevents the air from dissolving in the water. Cap the glass bottle tightly.

For bottle C: Place one iron nail in the glass bottle, and pour some water so that the iron nail is partially dipped. Keep this glass bottle unstoppered. This allows the iron nail to come into contact with both water and air.

Now, place all the glass bottles undisturbed at room temperature and observe the changes for 8 to 10 days. Record your observations in Table 4.3.

What do you think will happen? In bottle A, where there is dry air but no water, the iron nail will not develop brown deposits. In bottle B, where there is water but no air, the iron nail will also not develop brown deposits. But in bottle C, where there is both water and air, the iron nail will develop brown deposits. This brown deposit is called rust, and the process is called corrosion.

So, to recap, iron develops rust when it comes into contact with both air and water. This is called corrosion. The brown deposit is iron oxide.

Now, let's move to Section 4.3: Effect of Air and Water on Other Metals. Let's do Activity 4.6, which is a demonstration activity. Caution: It is advisable for students to wear protective eyeglasses and keep a safe distance.

Take a magnesium ribbon about 3 to 4 centimetres long. Clean it by rubbing with a piece of sandpaper. Hold it with a pair of tongs. Ignite the other end using a spirit lamp or a candle. Let the magnesium ribbon burn. What do you observe?

You must have observed that magnesium ribbon burns with a dazzling white flame and changes into a white powder. Collect it on a watch glass. This powder is magnesium oxide. It is formed due to the reaction between magnesium and oxygen present in the air.

Now, add a few drops of warm water to this white powder, stir it well, and check its nature. Recall the chapter 'Exploring Substances: Acidic, Basic, and Neutral'. Find out whether the solution of magnesium oxide is acidic or basic or neutral in nature. You can use any acid-base indicator.

What effect does this solution have on blue and red litmus papers? You would observe that it changes the colour of red litmus paper to blue; hence, it is basic in nature. Generally, oxides of metals are basic in nature.

Now, do you know that sodium is a metal which is stored in kerosene because it reacts vigorously with oxygen and water? A lot of heat is generated in the reaction. Storing sodium in kerosene prevents its exposure to moisture and air. Can you predict the nature of its oxide? Its oxide would be basic in nature, just like magnesium oxide.

Now, let's discuss some substances that do not behave like metals. This is Section 4.4.

Let's do Activity 4.7, which is also a demonstration activity. Caution: This activity must be performed in a fume hood or well-ventilated area. Burning sulfur produces gases, which can be harmful if inhaled.

Take a small amount of powdered sulfur in a deflagrating spoon. If a deflagrating spoon is not available, you may take a metallic cap of any bottle, wrap a metallic wire around it and give it the shape as shown in the figure. Heat it on a flame, and as soon as the sulfur starts burning, introduce the deflagrating spoon into a gas jar or glass tumbler. Cover the gas jar or glass tumbler with a lid to ensure that the gas produced does not escape.

Remove the lid after 3 to 4 minutes and take out the deflagrating spoon. Add a small quantity of water into the gas jar, quickly place the lid back and shake it so that the gas dissolves.

Now, recall the chapter 'Exploring Substances: Acidic, Basic, and Neutral'. Using an acid-base indicator, check whether the solution obtained after the addition of water to the gas jar is acidic or basic or neutral.

What do you observe? You would observe that it is acidic in nature. On burning sulfur in air, which contains oxygen, sulfur dioxide gas is formed. On dissolving sulfur dioxide gas in water, sulfurous acid is formed.

Now, let's do Activity 4.8. Take some sulfur powder in a glass tumbler. Add a small amount of water to it. What do you observe? You may have noticed that there is no reaction when sulfur is placed in water.

Substances like sulfur and phosphorus behave differently with air and water than metals. Phosphorus is stored in water as it catches fire when exposed to atmospheric air. These substances are usually soft and dull in appearance. They are neither malleable nor ductile, and they are not sonorous. They are also poor conductors of heat and electricity. These are called non-metals. Their oxides are acidic in nature.

Some other non-metals are oxygen, hydrogen, nitrogen, carbon, and so on. These must not be confused with materials such as plastic, glass, wood, rubber, and paper. These materials are not classified as metals or non-metals because they are not elements.

Now, let me tell you something interesting. Metals and non-metals are sub-categories of substances called elements. An element is a substance that cannot be broken down into simpler substances. Presently, 118 elements are known. These elements are the basic building blocks of all matter. Some are naturally occurring, while others are artificially made in the laboratory and do not exist in nature. You will study more about elements in higher grades.

Now, let's move to Section 4.5: Are Non-metals Essential in Everyday Life?

You often observe many metals in your day-to-day lives because of their distinct properties, such as their lustrous nature, heat and electrical conductivity, and high strength. However, this should not give an impression in your mind that non-metals are not important in our lives.

We breathe in oxygen, which is a non-metal, and without it, we would not be able to survive. Can you think of any other uses of oxygen? Oxygen is also used in hospitals for patients who have difficulty breathing. It is used in welding and cutting metals.

Carbon is essential in everyday life because it is the building block of all life forms. It is a key component of proteins, fats, and carbohydrates, which are necessary for growth and energy. Carbon is also used as fuel in the form of coal and natural gas.

Nitrogen is used in the manufacturing of fertilizers and other chemicals. It is an essential nutrient for the growth of plants. Nitrogen is also used in food packaging to keep food fresh.

Chlorine is a non-metal commonly used in water purification. It kills bacteria and other harmful microorganisms in water.

A solution of iodine, a non-metal, is applied on wounds as an antiseptic. Iodine tincture is used to clean wounds and prevent infection.

Now, let's look at the "In a Nutshell" section. This is a summary of everything we learned in this chapter.

We learned that metals and non-metals are differentiated based on their properties. Generally, metals are lustrous, whereas most non-metals are non-lustrous. Metals are generally malleable and ductile, while non-metals do not have these properties. Metals are good conductors of heat and electricity, but non-metals are generally poor conductors. Metals react with oxygen to produce metal oxides which are basic in nature. Non-metals react with oxygen to produce oxides which are acidic in nature. Generally, non-metals do not react with water. Metal objects get damaged when exposed to moist air, and the process is known as corrosion. Metals and non-metals have wide applications in everyday life.

Now, let's look at the "Let Us Enhance Our Learning" section. We need to solve all the questions. Let's go through them one by one.

Question 1: Which metal is commonly used to make food packaging materials as it is cheaper, and its thin sheets can be folded easily into any shape?

The options are: (i) Aluminium, (ii) Copper, (iii) Iron, (iv) Gold.

The answer is Aluminium. Aluminium is cheaper than copper and gold, and its thin sheets, which we call aluminium foil, can be folded easily into any shape. This is because aluminium is malleable.

Question 2: Which of the following metal catches fire when it comes in contact with water?

The options are: (i) Copper, (ii) Aluminium, (iii) Zinc, (iv) Sodium.

The answer is Sodium. Sodium reacts vigorously with water and catches fire. That is why sodium is stored in kerosene.

Question 3: State with reason(s) whether the following statements are True or False.

(i) Aluminium and copper are examples of non-metals used for making utensils and statues.

This is False. Aluminium and copper are metals, not non-metals. They are used for making utensils and statues.

(ii) Metals form oxides when combined with oxygen, the solution of which turns blue litmus paper to red.

This is False. Metal oxides are basic in nature. They turn red litmus paper to blue, not blue litmus paper to red. Blue litmus turning to red indicates an acidic solution.

(iii) Oxygen is a non-metal essential for respiration.

This is True. Oxygen is a non-metal, and it is essential for respiration. We breathe in oxygen to survive.

(iv) Copper vessels are used for boiling water because they are good conductors of electricity.

This is False. Copper vessels are used for boiling water because they are good conductors of heat, not electricity. Though they are also good conductors of electricity, that is not the reason for using them to boil water.

Question 4: Why are only a few metals suitable for making jewellery?

The answer is: Only a few metals are suitable for making jewellery because they need to have certain properties. They should be lustrous, durable, resistant to corrosion, and malleable enough to be shaped into beautiful designs. Gold and silver are the most commonly used metals for jewellery because they are lustrous, do not tarnish easily, and are highly malleable and ductile. Platinum is also used. Other metals may be too soft, too brittle, or may tarnish easily, making them unsuitable for jewellery.

Question 5: Match the uses of metals and non-metals given in Column I with the jumbled names of metals and non-metals given in Column II.

Let's look at Column I and Column II.

(i) Used in electrical wiring - The jumbled name is E N X Y G O, which is O X Y G E N. Wait, that doesn't make sense. Let me rearrange. E N X Y G O. If we rearrange, it could be O X Y G E N, which is oxygen. But oxygen is not used in electrical wiring. Let me think again. The jumbled name might be C O P P E R, which is copper. But the jumbled letters are E N X Y G O. Wait, let me look at the letters: E, N, X, Y, G, O. If we rearrange, we get G, O, X, Y, N, E. That doesn't make sense. Let me think of another metal used in electrical wiring. Aluminium is also used. The jumbled name could be U M I N I U M, but that doesn't match. Let me look at the next one.

Actually, let me think about this differently. For electrical wiring, we use copper and aluminium. Let me see which jumbled name matches. Column II has: (a) E N X Y G O, (b) N E C O H I R L, (c) P E P O R C, (d) T E N G O I N R, (e) O G D L.

Let's unscramble each:

(a) E N X Y G O - This could be O X Y G E N if we ignore the N. But we have all letters: E, N, X, Y, G, O. This could be rearranged as G, O, X, Y, N, E. That doesn't make a word. Maybe it's meant to be O X Y G E N, and the extra N is a mistake? Or maybe it's meant to be something else. Let me think. Actually, wait. Maybe the letters are meant to be rearranged to form O X Y G E N, and the N is extra? That doesn't make sense. Let me look at the other options.

(b) N E C O H I R L - This can be rearranged as C O P P E R. Wait, no. N, E, C, O, H, I, R, L. If we rearrange, we get C, O, P, P, E, R, L, I, H, N. That's too many letters. Let me count: N, E, C, O, H, I, R, L - that's 8 letters. But copper has 6 letters. Let me try again. N, E, C, O, H, I, R, L. If we take C, O, P, P, E, R, we have extra N, H, I, L. That doesn't work. Wait, maybe it's meant to be C O P P E R, and the extra letters are for something else? Let me look at the next one.

Actually, I think I misunderstood. Let me look at the table again. Column II has (a) E N X Y G O, (b) N E C O H I R L, (c) P E P O R C, (d) T E N G O I N R, (e) O G D L.

Now, let's unscramble each:

(a) E N X Y G O - This could be O X Y G E N, but that has 6 letters. We have 6 letters here: E, N, X, Y, G, O. That's 6 letters. So, (a) is O X Y G E N, which is oxygen. But oxygen is not used in electrical wiring. Wait, maybe I'm wrong. Let me check the number of letters. E, N, X, Y, G, O - that's 6 letters. So, it should be a 6-letter word. O X Y G E N is 6 letters. But oxygen is not used in electrical wiring. Hmm.

Wait, maybe the jumbling is different. Let me think of another word. E, N, X, Y, G, O. Could it be N, O, X, Y, G, E? No. Could it be G, O, X, Y, N, E? No. Let me try to think of a metal used in electrical wiring. Copper is used. But copper has 6 letters: C, O, P, P, E, R. The letters given are E, N, X, Y, G, O. That doesn't match. Aluminium has 9 letters. Not matching.

Wait, maybe I should look at the other options first.

(b) N E C O H I R L - That's 8 letters. Let me rearrange: C, O, P, P, E, R, L, I, H, N. That's 10 letters. Wait, let me count again: N, E, C, O, H, I, R, L - that's 8 letters. So, it should be an 8-letter word. What could it be? Maybe it's meant to be C H L O R I N E? But that's 8 letters: C, H, L, O, R, I, N, E. The letters given are N, E, C, O, H, I, R, L. That's exactly the same letters! So, (b) is C H L O R I N E, which is chlorine. But chlorine is not used in electrical wiring.

(c) P E P O R C - That's 6 letters. Rearranged: C, O, P, P, E, R. That's copper! So, (c) is copper. And copper is used in electrical wiring. So, (i) matches with (c).

(d) T E N G O I N R - That's 8 letters. Rearranged: N, I, T, R, O, G, E, N. That's nitrogen. So, (d) is nitrogen.

(e) O G D L - That's 4 letters. Rearranged: G, O, L, D. That's gold! So, (e) is gold.

Now, let's match:

(i) Used in electrical wiring - This should be copper. So, (i) matches with (c).

(ii) Most malleable and ductile - This should be gold. Gold is the most malleable and ductile metal. So, (ii) matches with (e).

(iii) Living organisms cannot survive without it - This should be oxygen. We need oxygen to breathe. So, (iii) should match with (a). But (a) was E N X Y G O, which we thought was oxygen. But wait, oxygen has 6 letters: O, X, Y, G, E, N. That's exactly the letters! So, (a) is oxygen. So, (iii) matches with (a).

(iv) Plants grow healthy when fertilizers containing it are added to the soil - This should be nitrogen. Fertilizers contain nitrogen. So, (iv) matches with (d).

(v) Used in water purification - This should be chlorine. Chlorine is used in water purification. So, (v) matches with (b).

So, the matches are: (i) with (c), (ii) with (e), (iii) with (a), (iv) with (d), (v) with (b).

Question 6: What happens when oxygen reacts with magnesium and sulfur? What are the main differences in the nature of products formed?

When magnesium reacts with oxygen, it forms magnesium oxide. This is a white powder. When we add water to magnesium oxide, it forms magnesium hydroxide, which is basic in nature. It turns red litmus paper blue.

When sulfur reacts with oxygen, it forms sulfur dioxide gas. When this gas dissolves in water, it forms sulfurous acid, which is acidic in nature. It turns blue litmus paper red.

So, the main difference is that metal oxides are basic in nature, while non-metal oxides are acidic in nature.

Question 7: Complete the following flow chart:

The flow chart shows: Question mark plus Air plus Heat, which leads to Ash. Then, Ash plus Water leads to Question mark. Then, Add blue and red litmus solutions separately. Then, Change in blue litmus solution leads to Question mark. Change in red litmus solution leads to Blue.

Let me think about this. The flow chart seems to be about burning something and testing the product. The starting material is unknown, but it produces ash when burned with air and heat. Then, water is added to the ash, and then we test with litmus papers.

If the change in red litmus solution is Blue, that means the solution turns red litmus paper blue. That indicates a basic solution. So, the product must be basic in nature.

Now, what could the original substance be? It could be a metal like magnesium. When magnesium burns in air, it produces magnesium oxide, which is basic. When we add water to magnesium oxide, it forms magnesium hydroxide, which is basic. So, the solution turns red litmus paper blue.

So, the unknown substance is a metal, specifically magnesium. So, the first question mark should be Magnesium. The second question mark, which is after adding water, should be Magnesium hydroxide or basic solution. The third question mark, which is the change in blue litmus solution, should be No change or remains blue, because the solution is basic, not acidic.

So, the complete flow chart is: Magnesium plus Air plus Heat leads to Magnesium oxide. Then, Magnesium oxide plus Water leads to Magnesium hydroxide solution. Then, Add blue and red litmus solutions separately. Then, Change in blue litmus solution: No change or remains blue. Change in red litmus solution: Turns blue.

Question 8: You are provided with the following materials. Discuss which material would be your choice to make a pan that is most suitable for boiling water and why?

The materials are: Iron, copper, sulfur, coal, plastic, wood, cardboard.

We need to make a pan for boiling water. What properties should the pan have? It should be able to conduct heat efficiently so that the water heats up quickly. It should be durable and not react with water. It should be safe to use.

Now, let's look at each material:

Iron: Iron is a good conductor of heat. It is durable and can withstand high temperatures. It is commonly used for making pans and utensils. However, iron can rust when exposed to water and air for a long time.

Copper: Copper is an excellent conductor of heat. It is used in some cooking vessels. However, copper can react with food and may be toxic in large amounts. It also needs to be cleaned regularly.

Sulfur: Sulfur is a non-metal. It is a poor conductor of heat. It would not be suitable for making a pan to boil water.

Coal: Coal is a non-metal. It is a poor conductor of heat. It would not be suitable for making a pan to boil water.

Plastic: Plastic is a poor conductor of heat. It would not be suitable for making a pan to boil water because it would not transfer heat efficiently. Moreover, plastic can melt when heated.

Wood: Wood is a poor conductor of heat. It would not be suitable for making a pan to boil water. However, wooden handles are used on pans because they do not conduct heat to our hands.

Cardboard: Cardboard is a poor conductor of heat. It would catch fire if heated. It is definitely not suitable for making a pan to boil water.

So, the best choices would be iron or copper. Between iron and copper, iron is more commonly used because it is cheaper and more widely available. Copper is a better conductor of heat, but it is more expensive and can react with food. So, iron would be the best choice for making a pan to boil water.

Question 9: You are provided with three iron nails, each dipped in oil, water and vinegar. Which iron nail will not rust, and why?

We have three iron nails: one dipped in oil, one in water, and one in vinegar.

We know that iron rusts when it comes into contact with both air and water. The nail dipped in oil: Oil forms a protective layer over the iron nail, preventing it from coming into contact with air and water. So, this nail will not rust.

The nail dipped in water: Water contains dissolved air. When the nail is dipped in water, it comes into contact with both water and air (dissolved in water). So, this nail will rust.

The nail dipped in vinegar: Vinegar contains water and air, and it is also acidic, which can accelerate rusting. So, this nail will definitely rust.

Therefore, the iron nail dipped in oil will not rust because the oil prevents air and water from coming into contact with the iron.

Question 10: How do the different properties of metals and non-metals determine their uses in everyday life?

Metals have several properties that make them useful in everyday life. They are lustrous, so they are used for making jewellery and decorative items. They are malleable, so they can be beaten into thin sheets and used for making foil, utensils, and sheets. They are ductile, so they can be drawn into wires and used for electrical wiring. They are good conductors of heat, so they are used for making cooking vessels. They are good conductors of electricity, so they are used for making electrical wires and components. They are sonorous, so they are used for making bells and musical instruments.

Non-metals also have important uses. Oxygen is essential for respiration. Carbon is the basis of all life and is used in fuels. Nitrogen is used in fertilizers. Chlorine is used for water purification. Iodine is used as an antiseptic. Sulfur is used in making sulfuric acid, which is important in many industries.

So, the properties of metals and non-metals determine their uses in our everyday life.

Question 11: One of the methods of protecting iron from getting rusted is to put a thin coating of zinc metal over it. Since sulfur does not react with water, can it be used for this purpose? Justify your answer.

No, sulfur cannot be used for protecting iron from rusting. Let me explain why.

The method of coating iron with zinc is called galvanization. Zinc protects iron in two ways. First, zinc is more reactive than iron, so it reacts with air and water first, forming zinc oxide or zinc hydroxide, which acts as a protective layer. Second, even if the zinc coating is broken, zinc being more reactive, will corrode instead of iron, thus protecting the iron.

Sulfur, on the other hand, is a non-metal. It does not react with water, but it also does not stick to iron properly. Moreover, sulfur is not as durable as zinc. Sulfur is also brittle and can easily crack or flake off. So, sulfur would not be a suitable coating for protecting iron from rusting.

Question 12: An ironsmith heats iron before making tools. Why is heating necessary in this process?

When an ironsmith heats iron before making tools, several things happen. First, heating makes the iron soft and malleable. This allows the ironsmith to beat it into the desired shape easily. Second, heating makes the iron easier to work with because it becomes more ductile. Third, heating helps to remove any impurities from the iron. Fourth, heating the iron to a high temperature makes it red hot, which allows the ironsmith to shape it into various tools and utensils. So, heating is an essential step in the process of making tools from iron.

Now, let's look at the Exploratory Projects. These are optional activities that you can do to enhance your learning.

First project: Dhokra, Bidriware, Pembarthi, and Kamrupi are some of India's famous metal art styles. Find out the states where these artworks are made. Also, make a collage of their photographs.

Dhokra is a famous metal craft from Chhattisgarh and Odisha. Bidriware is from Karnataka, specifically from Bidar. Pembarthi is from Telangana, specifically from Pembarthi. Kamrupi is from Assam. You can find more information about these and make a collage of their photographs.

Second project: On a map of India, mark the states where iron, gold, aluminium, and other metals are found.

Iron is found in states like Jharkhand, Odisha, Chhattisgarh, Karnataka, and Tamil Nadu. Gold is found in Karnataka, Rajasthan, and Andhra Pradesh. Aluminium is found in Odisha, Gujarat, Jharkhand, and Chhattisgarh. You can mark these on a map of India.

Third project: Explore the metals and non-metals found in smartphones and find out how they help the phone work properly.

Smartphones contain many metals like copper, gold, silver, aluminium, and lithium. Copper is used in wiring and circuits. Gold and silver are used in connectors and switches because they are good conductors and do not corrode. Aluminium is used in the phone's body because it is light and strong. Lithium is used in batteries. Non-metals like silicon are used in making computer chips. You can explore more about this.

Fourth project: Organise a classroom debate on whether the use of metals for comfort and luxury should be increased or decreased.

This is an interesting topic for debate. You can discuss the pros and cons of using metals for comfort and luxury. Some points could be: Metals are durable and long-lasting, but mining metals causes environmental damage. Using metals for luxury items can be wasteful, but metals can also be recycled. You can have a healthy debate on this topic.

Now, my dear students, we have come to the end of this chapter. Let me give you a brief summary of everything we learned today.

We started with the story of Yashwant and Anandi visiting an ironsmith. Then we learned about the properties of metals. We learned about malleability, which is the ability to be beaten into thin sheets. We learned about ductility, which is the ability to be drawn into wires. We learned about sonority, which is the ability to produce a ringing sound. We learned that metals are good conductors of heat and electricity.

Then we learned about non-metals and how they are different from metals. Non-metals are generally non-lustrous, not malleable or ductile, not sonorous, and poor conductors of heat and electricity.

We learned about the effect of air and water on metals. We learned that iron rusts when exposed to both air and water. We learned that magnesium burns in air to form magnesium oxide, which is basic in nature. We learned that sulfur burns in air to form sulfur dioxide, which dissolves in water to form sulfurous acid, which is acidic in nature.

We learned that metal oxides are basic in nature, while non-metal oxides are acidic in nature.

We learned about the uses of metals and non-metals in everyday life. We learned that metals are used for making utensils, wires, jewellery, and many other things. We learned that non-metals like oxygen, carbon, nitrogen, chlorine, and iodine are essential for our lives.

We also solved all the questions from the "Let Us Enhance Our Learning" section. We learned why aluminium is used for food packaging, why sodium catches fire in water, the difference between metal and non-metal oxides, and many other things.

This is the end of our lesson. I hope you enjoyed learning about the world of metals and non-metals. Remember, metals and non-metals are all around us, and they play important roles in our daily lives. Thank you for listening attentively. See you in the next lesson. Goodbye, students!