Questions & Answers: "The World of Metals and Non-metals"

Malleability is the property of metals that allows them to be hammered or pressed into thin sheets without breaking. This is why metals like aluminium are used to make foil. Ductility is the ability to be drawn into wires. Sonority refers to the property of producing a ringing sound when struck. Lustre is the shiny appearance of metals. Therefore, malleability is the correct property for making thin sheets. (2 marks = ~50 words)

Graphite is an allotrope of carbon, which is a non-metal. While most non-metals are poor conductors of electricity, graphite is an excellent conductor due to its unique atomic structure with free electrons. Sulphur, Oxygen, and Hydrogen are all non-metals, but they are insulators and do not conduct electricity. Therefore, graphite is the exceptional non-metal that conducts electricity. (2 marks = ~50 words)

Magnesium is a metal. When metals react with oxygen, they form metal oxides. These metal oxides are generally basic in nature. When magnesium oxide dissolves in water, it forms magnesium hydroxide, which is a base. This solution will turn red litmus paper blue, confirming its basic nature. Acidic solutions are formed by non-metal oxides. Neutral and amphoteric natures are not typical for simple metal oxides at this level. (3 marks = ~75 words)

Non-metals are generally brittle, meaning they break or crumble easily when subjected to force, such as hammering. This is in contrast to metals which are malleable and ductile. Non-metals typically lack lustre (are dull), are poor conductors of heat and electricity (with exceptions like graphite), and are not malleable or ductile. Therefore, brittleness is a characteristic property of most non-metals. (2 marks = ~50 words)

Rusting is a chemical change where iron reacts with oxygen and water (moisture) in the air to form hydrated iron(III) oxide, commonly known as rust. This changes the original substance (iron) into a new substance (rust) with different properties, making it a chemical change. Physical changes only alter the form, not the composition. Heat, light, or friction are not the primary causes of rusting. (3 marks = ~75 words)

Metals typically have a shiny appearance, a property known as lustre, which means they reflect light well. This makes them look bright and polished. Non-metals, on the other hand, usually lack this metallic lustre and appear dull, with the exception of diamond and iodine which are non-metals but possess lustre. Therefore, a shiny surface is a distinguishing characteristic of most metals.

The process described is called rusting. Rusting occurs when iron reacts with oxygen and moisture (water vapor) in the air. The reddish-brown flaky substance formed is hydrated iron(III) oxide ($Fe_2O_3.xH_2O$), commonly known as rust. This is a slow oxidation process. Burning involves rapid combustion and significant heat, which is not what happens here. Evaporation and sublimation are physical changes, not chemical reactions that form new substances like rust. Iron hydroxide and carbonate are not the primary products of typical iron rusting.

The ability of a material to be beaten into thin sheets is called malleability, and the ability to be drawn into thin wires is called ductility. These are characteristic physical properties primarily exhibited by metals. Non-metals, on the other hand, are generally brittle, meaning they break easily when hammered or stretched, and thus cannot be easily shaped into sheets or wires.

This observation is due to a displacement reaction. Copper is more reactive than silver. When a copper coin is dipped into silver nitrate solution ($AgNO_3$), the more reactive copper displaces the less reactive silver from its salt solution. The silver metal gets deposited on the copper coin, appearing as a shiny greyish-white coating. Simultaneously, copper goes into the solution to form copper nitrate ($Cu(NO_3)_2$), which is blue in colour, causing the solution to turn bluish. This demonstrates the reactivity series of metals, where a more reactive metal can displace a less reactive metal from its compound.

Most non-metals are poor conductors of electricity, acting as insulators. However, graphite is a unique allotrope of carbon that is an excellent conductor of electricity. This exceptional property, due to its specific crystalline structure where delocalized electrons are present, makes it suitable for use as an electrode in various electrochemical devices like dry cells. Its hardness is not its key property for this use (diamond is hard), nor is its slight lustre. Non-metals are generally unreactive with acids, so high reactivity is not a factor.

Malleability is the property of metals by which they can be beaten into thin sheets. The property of metals that allows them to be drawn into thin wires is called ductility.

Non-metals are generally poor conductors of heat and electricity. Metals are typically good conductors. Graphite, an allotrope of carbon (a non-metal), is an exception as it conducts electricity.

Metallic oxides are generally basic in nature (e.g., magnesium oxide). Non-metallic oxides are generally acidic in nature (e.g., sulfur dioxide). Some metallic oxides can be amphoteric.

According to the reactivity series, a metal that is more reactive can displace a less reactive metal from its compound in a solution. For example, iron can displace copper from copper sulphate solution.

Most metals are solid at room temperature, but mercury is a notable exception. It is the only metal that exists as a liquid at room temperature.

Key points: Luster, Malleability, Ductility, Conductivity (heat/electricity) for both metals and non-metals.

Key points: Metals as good heat conductors, wood/plastic as poor heat conductors (insulators), safety aspect.

Key points: Salt formation, Hydrogen gas production ('pop' sound test), Example (e.g., Zinc + HCl), Chemical equation.

Key points: Definition of displacement, Role of reactivity, Specific example (Iron & Copper Sulphate), Observation of change, Balanced chemical equation.

Key points: Oxygen (respiration), Carbon (pencil/diamond), Nitrogen (fertilizers), Chlorine (water purification). Any three well-explained uses are sufficient.