Test: The World of Metals and Non-metals - Class 7 MCQ

Non-metals are usually dull (not shiny) and brittle (they break easily). They do not bend like metals and do not conduct heat or electricity well.

Chlorine is used to purify water by killing harmful bacteria, making it safe to drink.

• Oxygen is a crucial element for respiration in living organisms.
• During respiration, organisms convert glucose and oxygen into energy, carbon dioxide, and water.
• This process provides the energy needed for growth, repair, and daily activities.
• Without oxygen, aerobic respiration cannot occur, leading to energy shortages.
• While other elements like carbon and nitrogen play roles in biological processes, oxygen is specifically vital for the respiration process.

• Rusting is a chemical process where iron reacts with oxygen and moisture in the air.
• Moist air contains water vapor, which is essential for rust to form.
• When iron is exposed to moisture, it oxidizes, leading to the formation of iron oxide (rust).
• High humidity accelerates this process, while dry air can slow it down.
• Thus, moist air is the primary cause of rusting in iron objects.

Painting or galvanizing iron creates a protective layer that prevents water and air from making contact with the iron.

Elements are the basic building blocks of all matter. They cannot be broken down into simpler substances.

Mercury is the only metal that is liquid at room temperature.

The oxide of magnesium (magnesium oxide) is basic. It can make a solution alkaline when dissolved in water.

Aluminium is light in weight, strong, resistant to corrosion, and can be alloyed with other metals. These properties make it ideal for building aircraft bodies.

Conductivity is the ability of a material to conduct electricity. Metals like copper are good conductors of electricity.

Malleability lets metals be shaped into thin sheets, like aluminum foil.

Sodium reacts vigorously with air and water, so it is stored in kerosene to prevent reactions.

Chlorine is used in water purification to kill bacteria and make water safe to drink.

Iron reacts with water and air to form rust (iron oxide), which weakens the metal.

Non-metals are brittle (they break easily) and are poor conductors of heat, unlike metals that are usually strong and conduct heat well.