Practice MCQ Questions and answers on Chemistry-GK

Mercury is a liquid metal.

Lustre (or luster) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning “light”, and generally implies radiance, gloss, or brilliance. Metals in general have high electrical conductivity, high thermal conductivity, and high density. Typically they are malleable and ductile, deforming under stress without cleaving. In terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, but gold leaf transmits green light. Metallic (or splendant) minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface. Examples include galena, pyrite and magnetite.

The non-metal found in the liquid state is bromine.

Bromine is a liquid non-metal.

Metals are an excellent conductor of electricity and heat because the atoms in the metals form a matrix through which outer electrons can move freely. Instead of orbiting their respective atoms, they form a sea of electrons that surround the positive nuclei of the interacting metal ions.

The first metal used by a man was copper.

White phosphorus is highly reactive, and spontaneously ignites at about 30°C in moist air. It is usually stored under water, to prevent exposure to the air.

The elements dissolved in sea water have been commercially extracted in many quantity. They are sodium and chlorine in the form of common salt, magnesium and some of its compounds, and bromine.

The rusting of iron is a/an electrochemical change.

When iron rusts, its weight increases.

Rusting is a type of oxidation reaction where iron reacts with oxygen in the presence of water or moisture in the air.

The chemical reaction can be summarized as follows:

4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃

The product of this reaction is iron(III) hydroxide, which further dehydrates to form iron(III) oxide, commonly known as rust.

During rusting, iron atoms combine with oxygen molecules from the air to form iron oxide.

This means that additional mass from oxygen is added to the iron, resulting in an increase in the overall weight of the iron object.

This process is not only a chemical change but also a physical one, as the rust occupies more volume than the original metal.

The increase in weight occurs because of the mass of the oxygen that has combined with the iron.

Therefore, when iron rusts, the addition of oxygen causes the weight of the iron to increase.