The World of Metals and Non-metals

Correct Option: (i) Aluminium

Justification: Aluminium is cheap, lightweight, and highly malleable — meaning it can be beaten into very thin sheets (aluminium foil) that can be folded easily into any shape. It is therefore widely used for food packaging materials such as foil wraps and containers.

Correct Option: (iv) Sodium

Justification: Sodium is an extremely reactive metal. When it comes in contact with water, it reacts vigorously, generating a large amount of heat that is sufficient to catch fire. This is why sodium is stored in kerosene to prevent its exposure to moisture and air.

(i) False [F]
Reason: Aluminium and copper are metals, not non-metals. Metals are used for making utensils and statues because of their malleability, ductility, and lustrous appearance.

(ii) False [F]
Reason: Metals react with oxygen to form metal oxides, and these oxides are basic in nature. A basic solution turns red litmus paper to blue, not blue litmus paper to red. It is the oxides of non-metals that are acidic in nature and turn blue litmus red.

(iii) True [T]
Reason: Oxygen is indeed a non-metal (it is a non-metallic element). All living organisms require oxygen for the process of respiration to release energy from food. Without oxygen, survival is not possible.

(iv) False [F]
Reason: Copper vessels are used for boiling water because copper is a good conductor of heat, not electricity. Good thermal conductivity allows heat to transfer quickly and uniformly to the water inside the vessel.

Given: We need to explain why only a few metals are used for making jewellery.

Concept: Jewellery requires metals with specific properties.

Answer:
Only a few metals are suitable for making jewellery because jewellery requires metals that possess all of the following properties:

1. Lustrous appearance: The metal must be shiny and attractive. Metals like gold, silver, and platinum have a natural shine that makes jewellery look beautiful.

2. High malleability and ductility: The metal must be easily shaped into intricate designs and drawn into fine wires or thin sheets without breaking.

3. Resistance to corrosion: Jewellery is worn regularly and exposed to air, moisture, and sweat. The metal must not rust or tarnish easily. Gold and platinum do not corrode, making them ideal.

4. Non-reactivity: The metal should not react with skin, sweat, or common chemicals.

5. Rarity and value: Precious metals like gold and silver are rare, which adds to their value as jewellery.

Most common metals like iron rust easily, and many metals are not lustrous enough or are too brittle for jewellery making. Hence, only metals like gold, silver, and platinum are widely used for jewellery.

Step 1: Decode the jumbled names in Column II.

- (a) ENXYGO → OXYGEN
- (b) NECOHIRL → CHLORINE
- (c) PEPORC → COPPER
- (d) TENGOINR → NITROGEN
- (e) OGDL → GOLD

Step 2: Match with Column I.

| Column I | Column II |
|---|---|
| (i) Used in electrical wiring | (c) PEPORC → Copper |
| (ii) Most malleable and ductile | (e) OGDL → Gold |
| (iii) Living organisms cannot survive without it. | (a) ENXYGO → Oxygen |
| (iv) Plants grow healthy when fertilisers containing it are added to the soil. | (d) TENGOINR → Nitrogen |
| (v) Used in water purification | (b) NECOHIRL → Chlorine |

Reasoning:
- Copper is an excellent conductor of electricity, so it is used in electrical wiring.
- Gold is the most malleable and ductile of all metals.
- Oxygen is essential for respiration; living organisms cannot survive without it.
- Nitrogen is an essential nutrient for plant growth and is a key component of fertilisers.
- Chlorine is widely used in water purification to kill harmful microorganisms.

Given: Reactions of oxygen with magnesium (a metal) and sulfur (a non-metal).

Reaction 1: Magnesium with Oxygen

When magnesium ribbon is burned in air (oxygen), it burns with a dazzling white flame and forms magnesium oxide (a white powder).

$$\text{Magnesium} + \text{Oxygen} \rightarrow \text{Magnesium oxide}$$
$$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$$

When magnesium oxide is dissolved in water, it forms magnesium hydroxide, which is basic in nature. It turns red litmus paper blue.

$$\text{MgO} + \text{H}_2\text{O} \rightarrow \text{Mg(OH)}_2$$

Reaction 2: Sulfur with Oxygen

When sulfur is burned in air (oxygen), it burns and forms sulfur dioxide gas.

$$\text{Sulfur} + \text{Oxygen} \rightarrow \text{Sulfur dioxide}$$
$$\text{S} + \text{O}_2 \rightarrow \text{SO}_2$$

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

$$\text{SO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{SO}_3 \text{ (Sulfurous acid)}$$

Main Differences in the Nature of Products:

| Property | Magnesium Oxide (Metal oxide) | Sulfur Dioxide (Non-metal oxide) |
|---|---|---|
| Nature | Basic | Acidic |
| Effect on red litmus | Turns red litmus blue | No change (already red) |
| Effect on blue litmus | No change | Turns blue litmus red |

Conclusion: Oxides of metals (like magnesium oxide) are basic in nature, whereas oxides of non-metals (like sulfur dioxide) are acidic in nature.

Note: The exact flow chart image is not fully visible in the OCR. However, based on the chapter content, the completed flow chart is described below:

$$\boxed{\text{Materials}}$$
$$\downarrow$$
$$\text{Metals} \quad \text{and} \quad \text{Non-metals}$$

Metals:
- Lustrous (shiny)
- Malleable (can be beaten into sheets)
- Ductile (can be drawn into wires)
- Sonorous (produce ringing sound)
- Good conductors of heat and electricity
- React with oxygen → form basic oxides
- React with moist air → undergo corrosion (rusting in case of iron)
- Examples: Iron, Copper, Aluminium, Gold, Silver

Non-metals:
- Generally non-lustrous (dull appearance)
- Not malleable
- Not ductile
- Not sonorous (produce dull sound)
- Poor conductors of heat and electricity
- React with oxygen → form acidic oxides
- Generally do not react with water
- Examples: Sulfur, Phosphorus, Oxygen, Nitrogen, Carbon, Chlorine

Given materials: Iron, Copper, Sulfur, Coal, Plastic, Wood, Cardboard

My choice: Copper (or Iron)

Best choice: Copper

Reasons:

1. Good conductor of heat: Copper is an excellent conductor of heat. This means heat from the flame transfers quickly and uniformly through the copper pan to the water, making boiling faster and more efficient.

2. Malleable and ductile: Copper can be easily shaped into a pan.

3. High melting point: Copper has a high melting point, so it does not melt or deform when placed on a flame.

4. Does not burn: Unlike wood or cardboard, copper does not catch fire.

Why the other materials are NOT suitable:

| Material | Reason Not Suitable |
|---|---|
| Sulfur | Non-metal; poor conductor of heat; melts and burns at low temperature |
| Coal | Non-metal; poor conductor of heat; burns in air |
| Plastic | Melts and burns at low temperatures; poor conductor of heat |
| Wood | Burns easily; poor conductor of heat |
| Cardboard | Burns easily; very poor conductor of heat; not strong |

Conclusion: Copper is the most suitable material for making a pan for boiling water because it is a good conductor of heat, has a high melting point, is malleable, and does not burn or corrode easily.

Given: Three iron nails dipped in — (1) Oil, (2) Water, (3) Vinegar.

Concept: Rusting of iron requires the simultaneous presence of both water (moisture) and air (oxygen). If either of these is absent, rusting does not occur.

Answer:

The iron nail dipped in oil will not rust.

Reason: When an iron nail is dipped in oil, the oil forms a protective coating around the nail. This coating prevents the nail from coming into contact with both moisture (water) and air (oxygen). Since rusting requires both water and oxygen simultaneously, the absence of these two factors prevents rusting.

What happens to the other nails:
- Iron nail in water: Water alone (without dissolved oxygen/air) causes very slow or negligible rusting. However, if the water is exposed to air, rusting will occur over time.
- Iron nail in vinegar: Vinegar is acidic in nature. Acid accelerates the corrosion of iron. The nail in vinegar will rust (corrode) faster than the nail in plain water.

Conclusion: The nail dipped in oil will not rust because oil acts as a barrier, preventing contact with water and air — the two essential requirements for rusting.

Given: We need to explain how properties of metals and non-metals determine their everyday uses.

Answer:

The properties of metals and non-metals directly determine how they are used in daily life:

Uses of Metals based on their Properties:

| Property of Metal | Use in Everyday Life |
|---|---|
| Good conductor of heat | Metals like copper and aluminium are used to make cooking vessels, pans, and boilers. |
| Good conductor of electricity | Copper and aluminium are used in electrical wires and cables. |
| Malleability (can be beaten into sheets) | Aluminium is beaten into thin foils used for food packaging. Iron is shaped into tools and machinery. |
| Ductility (can be drawn into wires) | Copper and aluminium are drawn into electrical wires. Steel wires are used in suspension bridges and cranes. |
| Sonority (produce ringing sound) | Metals are used to make bells, musical instruments like ghungroos, and school bells. |
| Lustre and durability | Gold and silver are used to make jewellery. |
| High strength | Iron and steel are used in construction of buildings, bridges, and vehicles. |

Uses of Non-metals based on their Properties:

| Property / Non-metal | Use in Everyday Life |
|---|---|
| Oxygen (supports life) | Essential for respiration; used in hospitals for patients. |
| Carbon (building block of life) | Present in all living organisms; used as fuel (coal). |
| Nitrogen (plant nutrient) | Used in manufacturing fertilisers for plant growth. |
| Chlorine (disinfectant) | Used in water purification to kill germs. |
| Iodine (antiseptic) | Applied on wounds to prevent infection. |
| Poor conductors of electricity (rubber, etc.) | Used as insulators for handles of screwdrivers, gloves for electricians. |

Conclusion: The specific physical and chemical properties of metals and non-metals make them uniquely suited for different applications in everyday life, industry, medicine, and technology.

Given:
- Iron is protected from rusting by coating it with zinc (a process called galvanisation).
- Sulfur does not react with water.
- Question: Can sulfur be used instead of zinc to protect iron from rusting?

Answer: No, sulfur cannot be used to protect iron from rusting.

Justification:

Although sulfur does not react with water, it cannot be used as a protective coating for iron for the following reasons:

1. Sulfur is a non-metal and is brittle: Sulfur is not malleable or ductile. It cannot be applied as a thin, uniform, and adherent coating over the surface of iron objects. It would crack and break off easily.

2. Poor adhesion: Sulfur does not bond well with the surface of iron, so it cannot form a continuous protective layer.

3. Sulfur reacts with air: Sulfur burns in air (oxygen) to form sulfur dioxide gas. Therefore, it does not provide a stable, long-lasting protective coating when exposed to air.

4. Zinc is more suitable: Zinc is a metal that is malleable and can form a thin, uniform, and strongly adherent coating over iron. Even if the zinc surface is scratched, zinc continues to protect the iron underneath because zinc is more reactive than iron and corrodes preferentially (sacrificial protection).

Conclusion: Sulfur, being a brittle non-metal that burns in air, is not suitable for protecting iron from rusting. Only metals like zinc, which can form a continuous, durable, and adherent coating, are suitable for this purpose.

Given: An ironsmith (blacksmith) heats iron before shaping it into tools.

Concept: Malleability of metals increases with temperature.

Answer:

Heating is necessary in the process of making iron tools for the following reasons:

1. Increased malleability: When iron is heated to a high temperature (until it becomes red hot or even white hot), it becomes soft and more malleable. This means it can be easily beaten with a hammer and shaped into the desired form (such as an axe, knife, or other tool) without cracking or breaking.

2. Easier shaping: At room temperature, iron is hard and rigid. It is very difficult to change its shape by hammering. Heating makes the iron soft enough to be moulded, bent, and shaped with relatively less effort.

3. Better workability: The heated iron can be pressed, stretched, and formed into intricate shapes that would be impossible to achieve with cold iron.

4. After shaping, the iron is cooled (sometimes rapidly in water — a process called quenching, or slowly in air), which makes it hard and strong again in the new desired shape.

Conclusion: Heating iron makes it soft and highly malleable, allowing the ironsmith to easily beat and shape it into tools using a hammer. Without heating, iron would be too hard and brittle to be shaped effectively.