Explanation

Mercury is the only elemental metal that remains in a liquid state at room temperature (around 25°C).

It is used in thermometers, barometers, and other scientific instruments due to this unique property.

Four other elements are liquids slightly warmer than room temperature.

They are:

1. Francium
2. Cesium
3. Gallium
4. Rubidium

Explanation

Natural graphite is used in many ways, from making pencils lead, to forming batteries.

The layered structure formed due to rings of carbon atoms present in Graphite makes it slippery and for that reason, it is used in Pencil leads.

Graphite was named by Abraham Gottlob Werner in 1789.

It is an allotrope of carbon.

Graphite is a good conductor of electricity.

Explanation

Salinity in seawater is defined as the total  weight of salt dissolved  in 1 kilogram of seawater.

Salinity is expressed in  g / kg and is often expressed in ppt (parts per 1000) or ‰ (permit).

Explanation

By mole fraction (i.e., by variety of molecules), dry air contains seventy eight.08% element, 20.95% oxygen, 0.93% argon, 0.04% greenhouse emission, and tiny amounts of alternative gases

Explanation

• Carbon dating is used to estimate the age of fossils.
• Those that are less than 60,000 years old.
• It is composed of organic materials like wood or leather.

Explanation

The chemical name of "chalk" is calcium carbonate.

It is commonly used in classrooms and as a dietary supplement due to its high calcium content.

Explanation

 Osmium is a chemical element with the symbol Os and atomic number 76.

Explanation

The position of an element in the periodic table is determined by its atomic number, which is the number of protons in the nucleus of an atom.

Atomic Number = Number of Protons

The periodic table is arranged in order of increasing atomic number.

Each element has a unique number of protons, which defines what element it is.

Explanation

Potassium is the chemical element 

symbol K 

atomic number 19

Electron configuration: 4s1

Electrons per shell: 2, 8, 8, 1

Explanation

Mercury is the only metal that is liquid at room temperature, unlike the others (Copper, Brass, Aluminum, Silver, Titanium, Platinum) which are solid.

It remains in liquid form due to its low melting point of about -38.83°C.