Nature of matter

Electrical conductivity is the property that describes how easily a substance permits electric charge or current to pass through it. A material with high conductivity contains charge carriers that can move relatively freely when a potential difference is applied. Metals such as copper and aluminium are common examples, so they are widely used in wires. The question asks for the name of the property, not for a description of a material’s appearance or its behaviour in another situation.

Therefore option A is correct. Volatility refers to how readily a substance changes into vapour. Brittleness means that a material breaks or shatters easily under force. Insolubility means that a substance does not dissolve in a particular solvent. None of these properties directly describes the passage of electric current. Electrical conductivity is thus the precise scientific term for the stated ability.

A substance that does not dissolve to form a solution in water is called insoluble. For example, sand does not dissolve in water. ‘Soluble’ is the opposite term because a soluble substance can dissolve in water. Exam tip: if a question states that a substance does not dissolve in water, choose insoluble.

Sand not dissolving in water is related to solubility, the ability of a substance to dissolve in a solvent. Sand is insoluble in water. Combustibility refers to the ability to burn, so it is not relevant here. Exam tip: Words such as “dissolves” or “insoluble” indicate the property of solubility.

The governing concept is the difference between physical and chemical properties. Combustibility is the ability of a substance to react with oxygen and burn, usually producing new substances such as carbon dioxide, water vapour, ash, and other products. Since wood can undergo this chemical change, its ability to burn is called combustibility, making option A correct. Melting point describes a change of state without necessarily changing chemical identity. Density compares mass with volume, and electrical conductivity describes the movement of electric charge. None of those properties specifically expresses the ability of wood to catch fire and continue burning.

The shiny appearance of a metal due to reflection of light from its surface is called metallic lustre. It is a physical property of metals, so metallic lustre is correct. Solubility refers to the ability of a substance to dissolve in a solvent and is unrelated to shine. Exam tip: associate a shiny, light-reflecting metal surface with metallic lustre.

Ductility is the property that enables a substance to be drawn into thin wires. Copper and aluminium are ductile metals, so they are used for electrical wires. Malleability means the ability to be hammered into sheets, not drawn into wires. Exam tip: remember ductility for wires and malleability for sheets.

Malleability is the property that allows a material to be hammered or beaten into thin sheets, so option A is correct. Ductility refers to drawing a material into wires, not sheets. Exam tip: associate sheets and foils with malleability.

The property by which metals produce a clear ringing sound when struck is called sonority. Therefore, sonority is the correct answer. Malleability means the ability to be beaten into thin sheets; it does not refer to producing sound. Exam tip: remember bells and cymbals as common examples of sonorous metals.

A substance is attracted by a magnet because of its magnetic property. For example, iron is magnetic and is attracted towards a magnet. Volatility describes the tendency to form vapour, solubility describes dissolution in a solvent, and combustibility describes the ability to burn; none of these causes magnetic attraction. Exam tip: remember iron, nickel, and cobalt as common magnetic materials.

Iron filings are attracted towards a magnet because iron is a magnetic material. Hence, this illustrates the property of magnetism. Combustibility refers to the ability to burn, and volatility refers to the tendency to vaporise easily; neither explains attraction by a magnet. Exam tip: magnetic separation is used to separate magnetic substances such as iron from a mixture.

A physical property can be observed or measured without changing the chemical identity of a substance. Density is a physical property because it is calculated from the relationship density = mass ÷ volume, and measuring mass and volume does not create a new substance. Therefore, option A is correct. The other three choices describe chemical behaviour: formation of a new substance during burning, rusting through reaction with oxygen and moisture, and reaction with an acid. These involve changes in composition and are therefore chemical properties. Density is often useful for identifying or comparing substances, although a complete identification may require more than one property.

Combustibility is related to burning and new substance formation. Exam tip: reaction-related properties are chemical.

A physical property can be observed or measured without changing a substance into a new substance. Boiling point is the temperature at which a liquid changes into a gas, so the substance undergoes only a change of state. Combustibility, rusting, and reaction with acid describe chemical behavior because they involve chemical changes. Therefore, option A is correct.

Fluidity is the property that describes a substance’s ability or tendency to flow, so it is correct for a liquid. Viscosity describes resistance to flow; a highly viscous liquid, such as honey, flows relatively slowly. Exam tip: remember that fluidity and viscosity indicate opposite flow tendencies.

Compressibility is the ability of a substance to decrease its volume when pressure is applied. Gases can be compressed easily because there are large spaces between their particles. Ductility is the ability to form wires, whereas malleability is the ability to form sheets. Exam tip: gases are much more compressible than solids and liquids.

Matter occupies some amount of physical space. The measure of that occupied space is called volume. A solid has a definite volume, while a liquid has a volume that can be measured even though its shape changes. A gas also occupies space, although its volume may depend on the container. Thus volume directly expresses the space taken up by a substance.

Option A is correct because volume is the relevant measurable property. Taste may describe some substances but does not measure space. Price is a commercial value, and a name is only a label; neither proves how much space matter occupies. Mass is another important property of matter, but it measures amount of matter rather than the space it takes. Therefore, the property asked for is volume.

Mass is the measure of the amount of matter present in an object, so option A is correct. The gravitational force acting on an object is called weight, not mass, while the space occupied by an object is its volume. Exam tip: the SI unit of mass is kilogram (kg), and mass does not change with location.

Mass measures the amount of matter present in an object, so mass is correct. Volume tells the space occupied by an object, while density is mass per unit volume; neither directly states the total amount of matter. Exam tip: mass is commonly measured in grams or kilograms.

Direct answer: Option A, pure substance. A pure substance contains only one kind of particle, so its particles have a definite composition and a definite change of state. On heating, it melts at one characteristic temperature, provided the pressure is fixed. Step by step: ice made of pure water melts at a fixed temperature; impurities disturb the regular arrangement and usually make melting occur over a range. A is correct because purity gives a sharp melting point. B, soil, contains sand, minerals, water and organic matter, so it is a mixture and has no single sharp melting point. C, air, contains several gases, so it is a mixture. D, lemonade contains water, sugar, acids and other substances, so it also melts over a range. Melting point can therefore help test purity, although pressure and the substance itself must also be considered. Memory cue: pure substance gives a sharp point; mixture usually gives a melting range.

The boiling point of a mixture can change with composition. Exam tip: separate properties of pure substances and mixtures.

The governing idea is that physical separation uses a physical difference without producing a new substance. Iron is attracted by a magnet, while many accompanying materials are not, so magnetic property can be used to remove iron from a mixture. This makes option A correct. Burning wood is a chemical change because new substances form. Making milk sour involves chemical transformations caused largely by fermentation, and rusting iron forms hydrated iron oxides through chemical reaction. In magnetic separation, the iron remains iron before and after the process; only its position in the mixture changes. Thus the example demonstrates the practical use of a physical property.

Oil and water are immiscible and differ in density. Exam tip: layer formation suggests separating funnel.

Direct answer: Option A, it easily forms vapour. Volatility means the tendency of a liquid to change into vapour easily. At the surface of every liquid, some particles have enough energy to escape. In a volatile liquid, intermolecular attraction is relatively weak or the particles escape readily, so evaporation is fast at ordinary conditions. Step by step: liquid particles move; some reach the surface; energetic particles leave; if many leave easily, the liquid is called volatile. A is correct. B is the opposite of volatility: a liquid that never forms vapour is not a normal volatile liquid. C describes a solid, not a liquid, and does not define volatility. D concerns magnetic behaviour, not evaporation; most common liquids do not stick to a magnet. Perfume and petrol are familiar examples because their smell or vapour spreads quickly. Memory cue: volatile means “flies away” as vapour easily.

The governing concept is that a physical property can be observed without altering the substance’s chemical composition. Colour is directly observed using the senses or instruments, and looking at it does not form a new substance. Therefore, option A is correct. Combustibility is a chemical property because testing it involves burning and producing new substances. Reaction with an acid is also chemical behaviour because the original substance is transformed into products. Rusting tendency describes a chemical reaction with oxygen and moisture, so it likewise concerns chemical change. Colour may help describe or identify a sample, although it should be used with other properties for reliable identification.

Testing combustibility may involve burning and new substances. Exam tip: chemical properties are tested through reactions.