Explanation

• Hydrogen and helium are the two lightest gases.
• Helium is the second most abundant element in the universe, after hydrogen.
• Helium has monatomic molecules.
• It is the lightest of all gases except hydrogen.
• Hydrogen is the lightest gas known.
• It provides the maximum lift for balloons due to its very low density.

Last updated question 17-02-2026

Explanation

• Carbon dioxide (CO₂) is used in fire extinguishers.
• It extinguishes fire by displacing oxygen and cooling the burning material.
• CO₂ fire extinguishers are especially effective for electrical and flammable liquid fires.
• Carbon dioxide is a colorless and non-flammable gas.
• It leaves no residue after use.

Explanation

• Mercury Symbol: Hg
• Atomic number: 80
• Melting point: -38.83 °C
• Atomic mass: 200.59 u

Last verified on 13-03-2026

Explanation

• The main reaction occurring in the Sun's core is nuclear fusion.
• In fusion, hydrogen nuclei combine to form helium, releasing a huge amount of energy.
• This energy is responsible for the Sun's light and heat.
• The Sun's primary fusion process is the proton–proton chain reaction.

Last verified on 01-09-2026

Explanation

• The atomic number of hydrogen is 1.
• It is the first element on the periodic table. 
• Named by: Antoine Lavoisier (1783)
• Atomic mass: 1.00784 u
• Appearance: Colorless gas
• Symbol: H
• Protons: 1
• Electrons: 1

Last updated 26-07-2026 by NA

Explanation

• Freezing Point: 0°C
• Fahrenheit: 32°F
• Kelvin: 273.15 K

Additional information:

• Boiling Point: 100°C (212°F or 373.15 K)
• Standard Atmospheric Pressure: 1 atm (760 mmHg)

Last verified on 06-07-2026

Explanation

• Fluorescent lamps mainly use argon gas (often with a small amount of mercury vapor).
• Electric current excites the gas and produces ultraviolet (UV) light.
• The UV light then hits the phosphor coating inside the tube.
• This coating produces visible light.
• Argon helps in starting and maintaining the discharge.

Last verified on 14-06-2026

Explanation

• The usual gases used for lifting airships are hydrogen and helium.
• Hydrogen is the lightest known gas and thus has great lifting capacity,
• Helium is not as buoyant but is far safer than hydrogen because it does not burn.

Last verified on 01-04-2026

Explanation

• Natural gas burns with a clean blue flame.
• It indicates complete combustion.
• Blue flame produces more heat and less smoke.
• It is efficient and less polluting.
• Natural gas mainly contains methane (CH₄).

Last verified on 24-05-2026

Explanation

• Effusion is the escape of gas molecules through a tiny hole.
• According to Graham’s law, rate of effusion ∝ 1/√molar mass.
• Lighter gases effuse faster than heavier gases.
• Among given options, hydrogen has the lowest molar mass (H₂ = 2 g/mol).
• Therefore, it moves and escapes the fastest.

Last verified on 19-05-2026