Test: Metals and Non-metals - Class 7 MCQ

Mercury is commonly used in dental amalgams for fillings due to its ability to form a durable and stable compound with other metals. This property allows dental fillings to withstand the pressures of chewing while maintaining their integrity.

Rusting requires both air and water to occur. The combination of oxygen from the air and moisture creates the ideal conditions for iron to oxidize, leading to rust formation.

Metalloids can form alloys when mixed with metals, combining properties of both categories. This versatility makes them valuable in various applications, especially in electronics where semiconductors are needed.

Iodine appears as a dark grey crystalline solid that sublimates to form a violet gas upon heating. Its unique physical properties make it useful in various applications, including antiseptics and dietary supplements.

Vulcanization involves treating rubber with sulfur to enhance its strength and elasticity. This process improves the material's durability and performance, making it suitable for various applications, including tires and seals.

Noble metals like gold, silver, and platinum are known for their resistance to oxidation and corrosion. This resistance makes them ideal for applications where durability and longevity are essential.

Oxygen is vital for respiration as it is required by most living organisms to produce energy. Its role in cellular respiration is critical for sustaining life, making it one of the most important elements.

Heating does not prevent rusting; instead, it can accelerate oxidation. Methods like galvanization (coating with zinc), oiling, and painting create barriers that protect iron from moisture and oxygen, thereby preventing rust formation.

Corrosion occurs when reactive metals interact with moisture and oxygen in the environment, leading to the formation of compounds on their surfaces. This process can degrade the metal over time, making it appear dull and potentially compromising its structural integrity.

Zinc is primarily used for galvanizing iron and steel to protect them from rust and corrosion. This process extends the life of metal structures and components, making it a crucial application in construction and manufacturing.

Platinum is classified as a noble metal because it is highly resistant to corrosion and oxidation, making it valuable for various applications including jewelry and industrial uses. Unlike more reactive metals, noble metals maintain their luster and integrity over time.

Silver is the best conductor of electricity, followed closely by copper. This high conductivity is why silver is often used in electrical applications, although its cost limits its use compared to copper.

Chlorine is widely used to sterilize drinking water because it effectively kills bacteria and other pathogens. Its strong oxidizing properties make it an essential chemical in public health and sanitation.

Non-metals are generally brittle and cannot be shaped into thin sheets or drawn into wires, unlike metals which exhibit malleability and ductility. This brittleness is a defining feature of most non-metals.

Stainless steel is commonly used for cutlery because it is resistant to corrosion and staining while maintaining strength and durability. This makes it ideal for kitchenware and dining utensils.