Class 7 Science Curiosity Chapter 4 MCQ – The World of Metals and Non-metals

Aluminium can be made into thin sheets because it is malleable. These sheets can be folded around food easily. Its comparatively low cost makes aluminium a practical packaging material when compared with expensive metals such as gold and silver.

Sodium reacts vigorously with water and releases a large amount of heat. The chapter explains that sodium is stored in kerosene to keep it away from water and air, which would otherwise react with the metal.

Malleability is the ability of a material to be beaten into thin sheets. Most metals show this property. It explains why metals can be used to make items such as aluminium wrapping foil and thin silver foil.

Ductility is the ability to be drawn into wires. The chapter explains that metals commonly possess this property and gives examples involving electrical wires, ornaments, and the metal strings used in several musical instruments around us.

Sonority is the property that allows metals to produce a ringing sound when struck or dropped. The chapter connects this property with familiar objects such as school bells and ghungroos, which are made using suitable metals.

Although metals are generally hard, sodium and potassium are important exceptions mentioned in the chapter. They are soft enough to be cut with a knife. This shows why the word “generally” matters when describing the properties of metals.

Mercury is the metal identified in the chapter as liquid at room temperature. Most familiar metals are solid under these conditions, so mercury is an exception to the common idea that every metal must be a solid.

Gold and silver are described as the most malleable metals, meaning they can be made into very thin sheets. Malleability concerns forming sheets, while ductility concerns drawing wires; the two properties should not be confused with each other.

Coal and sulfur break into pieces when hammered in the activity, so they are described as brittle. Unlike the metals tested, they do not flatten into thin sheets. This contrast helps explain the meaning of malleability.

Metals allow heat to pass through them easily, making them useful for cooking vessels. Heat can travel through the vessel to its contents. Handles are often made from poorer conductors so that they do not become hot as easily.

A handle made from an insulating material does not allow electricity to pass through easily. The chapter uses screwdriver coverings and rubber gloves as examples of poor conductors that help protect a person from contact with conducting parts.

The iron nail exposed to both air and water develops brown rust. Nails kept in dry air alone or in water from which air is excluded do not show the same deposit. The comparison shows that both are needed.

Silica gel keeps the air inside the bottle dry by removing moisture. This allows the experiment to test iron in air without water being available. The nail does not develop the brown deposit seen when both air and water are present.

Boiling removes dissolved gases from the water, and the oil layer helps prevent air from entering it again. This arrangement tests the nail in water while excluding air, allowing a comparison with the nail exposed to both conditions.

Corrosion is the gradual damage to metal surfaces through contact with substances in their surroundings. Rusting of iron is one example. The chapter also mentions a green coating on copper and a black coating on silver as other examples.

Galvanisation places a protective layer of zinc on iron. This helps protect the iron from conditions that cause rusting. The chapter lists it alongside painting, oiling, and greasing as methods used to reduce the damage caused by rust.

Magnesium burns with a dazzling white flame and combines with oxygen in the air to form magnesium oxide. The white powder is a new substance. When tested with water, it shows the basic nature described for this metal oxide.

Burning sulfur produces sulfur dioxide. When this gas dissolves in water, sulfurous acid forms and the solution shows acidic behaviour. This contrasts with the basic result obtained when the magnesium oxide produced in another activity is tested.

The chapter explains that metals and non-metals are groups of elements. Materials such as wood, plastic, glass, rubber, and paper are not elements. Being unlike a metal in appearance does not automatically make a material a non-metallic element.

Chlorine is the non-metal mentioned for water purification. The chapter also describes other useful non-metals, including oxygen for respiration and nitrogen in fertilisers. These examples show that non-metals have important everyday uses as well as metals.

Making a thin sheet by hammering requires malleability. A material that is brittle would break instead of flattening as desired. The chapter’s metal-working examples connect the choice of a material with the particular property needed for the job.

Ductility allows a metal to be drawn into a thin wire, which can be used as an instrument string. The chapter mentions instruments such as the sitar and guitar to show how this property is useful in everyday objects.

Sodium challenges the claim that every metal is hard, while mercury challenges the claim that every metal is solid at room temperature. Together, these examples show that common metal properties have exceptions and should not be stated as absolute rules.

The pan needs to transfer heat to its contents, so a metal body is useful. The handle should transfer heat less readily to the hand, so wood is suitable. Different parts use different properties to serve different purposes.

Moist air supplies both air and water, the two conditions needed for rusting in the chapter’s experiment. Dry air lacks the necessary moisture. The comparison therefore predicts that the nail exposed to moist air is more likely to rust.

Rusting needs contact with air and water. A suitable paint coating helps keep these away from the iron surface. This is why painting is listed in the chapter as a practical method for protecting iron objects from rusting.

The white product is magnesium oxide, and the mixture obtained with water is basic in the activity. A basic mixture turns red litmus blue. This result helps distinguish it from the acidic solution formed after burning sulfur.

The chapter names chlorine for water purification and nitrogen for making fertilisers. Matching each substance to its stated use gives the correct order. The examples also show that different non-metals serve different practical needs in daily life.

Poor conductivity alone does not establish that something is a non-metallic element. The chapter clearly separates elements from materials such as wood. Wood can have properties unlike metals without belongin

The chapter explains that metals such as iron and aluminium are recycled to minimise waste and contribute to sustainability. Reusing these materials connects the useful properties of metals with responsible choices about the resources we use.