Exploring Metals and Their Properties

Which of the following is an alloy commonly used in the construction of aircraft due to its strength and light weight?

• Brass

• Stainless steel

• Duralumin

• Bronze

Answer explanation

Duralumin is an alloy of aluminum and copper, known for its high strength-to-weight ratio, making it ideal for aircraft construction. In contrast, brass, stainless steel, and bronze are heavier and less suitable for this application.

Which allotrope of carbon is the hardest known natural material?

• Graphite

• Diamond

• Fullerenes

• Charcoal

Answer explanation

Diamond is the hardest known natural material due to its strong covalent bonding and crystal structure, making it superior in hardness compared to other allotropes like graphite, fullerenes, and charcoal.

Which of the following best describes the electrical conductivity of metals?

• Metals are poor conductors of electricity.

• Metals are good conductors of electricity.

• Metals do not conduct electricity at all.

• Metals only conduct electricity when dissolved in water.

Answer explanation

Metals are good conductors of electricity due to the presence of free-moving electrons that facilitate the flow of electric current. This property distinguishes them from insulators, which do not conduct electricity well.

Which of the following is NOT an alloy?

• Bronze

• Steel

• Graphite

• Brass

Answer explanation

Graphite is a form of carbon and not an alloy, which is a mixture of two or more metals. Bronze, steel, and brass are all alloys made from different metal combinations.

Which property is typical of non-metals?

• High melting point

• Good electrical conductivity

• Dull appearance

• Malleable

Answer explanation

Non-metals typically have a dull appearance, unlike metals which are shiny. They also tend to have low melting points, poor electrical conductivity, and are not malleable, making 'dull appearance' the correct choice.

Which of the following is a use of stainless steel?

• Electrical wiring

• Cutlery and kitchen sinks

• Pencils

• Jewellery

Answer explanation

Stainless steel is commonly used for cutlery and kitchen sinks due to its resistance to corrosion and ease of cleaning. Other options like electrical wiring and pencils do not typically use stainless steel.

Which allotrope of carbon is used as a lubricant and in pencils?

• Diamond

• Graphite

• Charcoal

• Amorphous carbon

Answer explanation

Graphite is the allotrope of carbon used as a lubricant and in pencils due to its layered structure, allowing layers to slide over each other easily. Diamond, charcoal, and amorphous carbon do not have these properties.

Which of the following statements about alloys is correct?

• Alloys are pure elements.

• Alloys are mixtures of two or more elements, at least one of which is a metal.

• Alloys are always non-metals.

• Alloys cannot conduct electricity.

Answer explanation

The correct statement is that alloys are mixtures of two or more elements, with at least one being a metal. This distinguishes them from pure elements and non-metal substances.

Which of the following is a property of non-metals?

• Sonorous

• Ductile

• Poor conductor of heat

• Lustrous

Answer explanation

Non-metals are generally poor conductors of heat, unlike metals which are good conductors. The other options, such as sonorous, ductile, and lustrous, are properties associated with metals.

Which of the following is an example of an alloy and its main use?

• Brass – used in coins and musical instruments

• Graphite – used in batteries

• Diamond – used in pencils

• Iron – used in jewellery

Answer explanation

Brass is an alloy made primarily of copper and zinc. It is commonly used in coins and musical instruments due to its durability and acoustic properties, making it the correct choice among the options provided.