Explanation

• The hardest substance in the world is diamond.
• Its hardness is due to the strong covalent bonding between its carbon atoms.
• This making it the most resistant to scratching.

Additional information:

• Category: Native minerals
• Cleavage: 111 (perfect in four directions)
• Crystal class: Hexoctahedral (m3m); H-M symbol: (4/m 3 2/m)
• Crystal habit: Octahedral
• Crystal system: Cubic
• Dana classification: 1.3.6.1
• Density: 3.5–3.53 g/cm3 3500–3530 kg/m3

Last verified on 07-06-2026

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

• Meteorology is the scientific study of the atmosphere, especially weather and climate.
• It involves forecasting and understanding atmospheric phenomena.
• Meteorology is a branch of the atmospheric sciences.
• Metrology is the scientific study of measurement.

Last verified on 03-04-2026

Explanation

• Gamma rays have the highest penetrating power among these particles.
• Due to their lack of mass and charge.
• It allowing them to pass through most materials.

Additional information:

• Alpha radiation has the lowest penetrating power.

Last verified on 12-04-2026

Explanation

• Isotopes of an element have the same number of protons.
• They differ in number of neutrons, which changes mass number.
• Chemical properties remain almost the same due to same protons.

Last verified on 14-05-2026

Explanation

• Total bones in adult human body = 206
• At birth = 270–300 bones (fuse to become 206)

The total bones of our body can be divided into:

• Axial skeleton = 80 bones
• Appendicular skeleton = 126 bones

Additional information:

• Newborn baby has 300 bones
• Longest bone = Femur
• Shortest bone = Stapes
• Bones in human skull = 22

Last verified on 30-03-2026

Explanation

• The Sun is a star.
• There are lots of stars, but the Sun is the closest one to Earth.
• It is the center of our solar system.
• The Sun is a hot ball of glowing gases.
• The sun is composed of layers made up almost entirely of hydrogen and helium.

Last verified on 13-03-2026

Explanation

• Humidity is the amount of water vapor present in the air.
  • It affects weather, climate, and comfort levels.
  • High humidity can make the air feel hotter, low humidity feels drier.
  • Measured using a hygrometer.
  • Important in agriculture, meteorology, and human health.

Last verified on 05-02-2026

Explanation

• Sunlight is a good source of vitamin D.
• When our skin is exposed to sunlight, it produces vitamin D, 
• It is essential for bone health, immune function, and the regulation of calcium levels in the blood.
• Deficiency of Vitamin D results in Rickets.

Explanation

• Sound waves are mechanical waves and need a medium to travel.
  • They travel fastest in solids, slower in liquids, and slowest in gases.
  • Solid particles are closely packed, allowing rapid vibration transfer.

Last verified on 04-02-2026