Nature of matter

Mercury is a metal that remains liquid at room temperature (about 25°C). Its melting point is about
-39°C, so it is molten under ordinary room conditions. Iron, aluminium and copper have much higher melting points and are solids at room temperature. Exam tip: remember mercury as the standard example of a liquid metal at room temperature.

Bromine is a non-metal that is liquid at ordinary room temperature. Most non-metals are solids or gases, so bromine is an important example to remember. Its liquid form does not make it a metal; physical state and metallic character are different ideas. Mercury is another familiar element that is liquid at room temperature, but mercury is a metal, whereas bromine is a non-metal.

Therefore, the correct choice is B, liquid non-metal. The other choices fail because bromine is not a solid, it is not a metal, and it is not classified as a metalloid. The answer follows by identifying both properties separately: bromine belongs to the non-metals and its state at room temperature is liquid.

Direct answer: Option B, drawn into wires. Ductility is the property of a material that allows it to be stretched or pulled into thin wires without breaking. Metals often show this property because their particles can shift while the metallic bonding remains effective. Step by step: apply a pulling force to a metal; if it can become a long, thin wire instead of snapping, it is ductile. Copper and aluminium are familiar examples used for electrical wires. Option A, beaten into sheets, describes malleability, not ductility. Malleability is the ability to be hammered or pressed into thin sheets. Option B is correct because “wire” is the key word in the definition of ductility. Option C, dissolving in water, is solubility, which is a different property and is not the meaning of ductility. Option D, changing into gas, is vaporisation or conversion to a gaseous state, usually by heating, and is unrelated to mechanical shaping. Do not confuse ductility with malleability: ductility is tested by pulling into wire, while malleability is tested by hammering into sheets. Memory cue: “Ductility—drawn into wire; malleability—made into a sheet.”

Malleability is the property by which a metal can be hammered into thin sheets without breaking. Hence, option B is correct; for example, gold can be made into very thin gold leaf. Option A describes ductility, which is the ability to be drawn into wires. Exam tip: associate sheets with malleability and wires with ductility.

Gold is a chemical element that shows characteristic metallic properties such as lustre, malleability, and electrical conductivity. Therefore, it is a metal. Metalloids have a mixture of metallic and non-metallic properties, whereas gold is distinctly metallic. Exam tip: Remember Fe, Cu, Ag, and Au as metals.

Sulfur is a non-metal. It is usually a yellow solid and does not conduct electricity well, which are typical non-metallic properties. Metalloids show a mixture of metallic and non-metallic properties, but sulfur is not a metalloid. Exam tip: remember sulfur, oxygen, and phosphorus as common non-metals.

Boron is a metalloid because it shows some properties of both metals and non-metals. It can behave as a semiconductor, so it is classified as a metalloid rather than as a metal or non-metal. A mixture is a physical combination of two or more substances, whereas boron is an element. Exam tip: several metalloids are found near the zigzag line in the periodic table.

Sonority is the property of metals by which they produce a clear ringing sound when struck. Therefore, option A is correct. Dissolving in water is not a general property of metals and is unrelated to sonority. Exam tip: remember the ringing sound of a bell, coin, or metal plate as an example of sonority.

The governing concept is that general classifications have important exceptions. Graphite is an allotrope of carbon, and carbon is a non-metal. In graphite, each carbon atom forms three strong covalent bonds, leaving one electron per atom relatively delocalized across the layered structure. These mobile electrons allow graphite to conduct electricity, even though most non-metals are poor conductors. Sulfur and phosphorus are non-metals but do not normally conduct electricity well, while chlorine is a molecular gaseous non-metal and is also not a good conductor. Therefore option A is the only correct answer.

Diamond is an allotrope of carbon. In diamond, each carbon atom is strongly covalently bonded to four other carbon atoms, which makes it extremely hard. Silicon is in the same group as carbon, but diamond is not a form of silicon. Exam tip: diamond and graphite are both allotropes of carbon, but they have different structures.

Graphite is an allotrope of carbon. In graphite, each carbon atom is bonded to three other carbon atoms in layers; therefore, it conducts electricity and is used in pencil leads. Diamond is also an allotrope of carbon, whereas silicon and sulfur are different elements. Exam tip: Remember diamond, graphite and fullerenes as major allotropes of carbon.

The governing concept is allotropy. Allotropy is the ability of the same element to exist in two or more different structural forms, usually in the same physical state. These different forms are called allotropes. Their atoms may be arranged differently or joined by different bonding patterns, so their physical and sometimes chemical properties can differ greatly. Carbon illustrates this clearly: diamond has a rigid three-dimensional structure and is extremely hard, whereas graphite has layered sheets, is soft, and conducts electricity. Both substances contain only carbon atoms. Thus option B gives the correct simple meaning. Option A incorrectly says there is only one form, while options C and D describe mixing or a change of state, not a structural variation of one element.

Oxygen
(O_2
) and ozone
(O_3
) are different forms of the same element, oxygen. Such different forms of an element are called allotropes, so the concept is allotropy. A homogeneous mixture contains two or more substances uniformly mixed, whereas
(O_2
) and
(O_3
) are not mixtures. Exam tip: different structural forms of the same element indicate allotropy.

At room temperature, most metals are solids because the attractive forces between their particles are relatively strong. Mercury is an important exception because it is liquid at room temperature; therefore, it is incorrect to say that all metals are solid. Exam tip: notice the word “usual” and remember mercury as the liquid-metal exception.

Non-metals can occur in all three physical states. For example, carbon and sulphur are solids, bromine is a liquid, and oxygen and nitrogen are gases. Therefore, option B is correct. Saying that non-metals are only liquids or only gases is incorrect because many non-metals are solids. Exam tip: remember bromine as a non-metal that is liquid at room temperature.

Nitrogen is a gas at ordinary temperature and pressure and is a non-metal, so nitrogen is correct. However, oxygen and chlorine are also gaseous non-metals, so the given question has more than one correct option. Exam tip: in such questions, check both the physical state and classification of every option; a valid MCQ should contain only one correct answer.

Iron is a metal, whereas sulfur is a non-metal. Therefore, iron and sulfur form the correct metal–non-metal pair in the required order. Option B contains the same elements in the reverse order, so it is not correct. In options C and D, both elements are non-metals. Exam tip: check both the type of each element and the order asked in the pair.

Sodium is not a metalloid; it is an alkali metal in Group 1 of the periodic table. Boron, silicon, and germanium are metalloids and show some properties of both metals and non-metals. Exam tip: remember that Group 1 elements are alkali metals.

Ductility is the property of a material that allows it to be drawn or stretched into thin wires without breaking. Copper has considerable ductility, which is why it can be processed into long electrical wires and other thin forms. The property does not mean that copper dissolves, evaporates, or breaks easily.

Thus option B, ductility, is correct. Brittleness would make a material crack or break during drawing, which is the opposite of what wire-making requires. Volatility concerns how easily a substance changes into vapour, while solubility concerns dissolving in a solvent; neither property explains the formation of copper wire. The clue is the word “wires”: drawing a metal into wire is directly associated with ductility.

The governing concept is the distinction between malleability and ductility. Malleability is the ability of a material to be beaten, pressed, or rolled into thin sheets without breaking. Aluminium can therefore be rolled into the extremely thin sheets used as aluminium foil, making option A correct. Ductility is different: it is the ability to be drawn into wires, so it is associated with cables rather than foil. Inertness describes limited chemical reactivity and may help explain some uses, but it does not produce a sheet. Sublimation is the direct change from solid to gas and is unrelated to foil manufacture.

Sulfur is a non-metal and does not show metallic lustre. Exam tip: use lustre to identify metals but remember exceptions.

Chlorine is a non-metal and occurs as a yellowish-green gas at ordinary temperature. Iron, magnesium, and zinc are metals and show metallic properties such as lustre and electrical conductivity. A common confusion is that chlorine is an element, but not every element is a metal. Exam tip: halogens in Group 17 of the periodic table are generally non-metals.

Oxygen is a gas at room temperature and is an element because it contains only oxygen atoms. Water is a compound, brass is an alloy of copper and zinc, and sodium chloride is also a compound. Exam tip: identify both the physical state and whether a substance is an element, compound, or mixture.

The shiny appearance of a metal is called metallic lustre. Free electrons in metals reflect light, producing this characteristic shine. Ductility means the ability to be drawn into wires, not shine. Exam tip: distinguish metallic lustre from other physical properties such as ductility and malleability.

The governing concept is the intermediate nature of metalloids. Metalloids are elements whose properties lie between those of metals and non-metals, so option C is correct. Depending on the element and the property being considered, they may show metallic appearance or limited conductivity while also displaying non-metal-like chemical behavior. Silicon and germanium, for example, are important semiconductors because their electrical conductivity is neither as high as that of metals nor as low as that of insulators. Option A and option B are too absolute, while option D confuses a physical state with a chemical classification. Thus both kinds of properties are possible.