Explanation

• The human body contains about 65% oxygen by mass.
• Oxygen is the most abundant element in the human body.
• It is mainly present in water (H₂O) and organic compounds.
• It is essential for respiration and energy production.

Additional information:

• Carbon: ~18%
• Hydrogen: ~10%
• Nitrogen: ~3%
• Other elements: ~4% (calcium, phosphorus, etc.)

Last verified 09-06-2026

Explanation

• The thickness of Earth is about 13,700 kilometers (8,500 miles).
• The mantle, which is the biggest part of Earth by volume.
• It is approximately 2,900 kilometers (1,800 miles) thick. 

Last verified on 09-06-2026

Explanation

• Herpetology is the branch of zoology that studies reptiles and amphibians.
• Reptiles include: snakes, lizards, crocodiles, turtles.
• Amphibians include: frogs, toads, salamanders.
• The word comes from Greek “herpeton” meaning creeping animal.

Last verified on 09-06-2026

Explanation

• The splitting of light into its constituent colors is called dispersion.
• White light splits into seven colors (VIBGYOR).
• It occurs when light passes through a prism.
• Different colors bend at different angles.
• This creates a spectrum of colors.

Last verified on 08-06-2026

Explanation

• The ecosystem is the structural and functional unit of the environment.
• Ecosystem = Biotic + Abiotic components
• Biotic: plants, animals, microorganisms
• Abiotic: water, air, soil, sunlight

Last verified on 08-06-2026

Explanation

When white light passes through a prism, it splits into 7 colors, forming a spectrum known as a rainbow:

1. Red
2. Orange
3. Yellow
4. Green
5. Blue
6. Indigo
7. Violet

The separation of visible light into its different colours is known as dispersion.

Last verified on 08-06-2026

Explanation

• Sublimation is the direct transition of a solid into a gas without passing through the liquid phase.

Additional information:

Some common sublimating substances:

• Dry ice (CO₂) – solid → gas
• Iodine crystals – solid → violet gas
• Camphor – solid → vapor
• Naphthalene (mothballs) – solid → gas
• Ammonium chloride – solid → gas

Last verified on 13-03-2026

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

• Photosynthesis produces glucose and oxygen.
• Green plants use sunlight, water, and carbon dioxide.
• This process occurs in chloroplasts using chlorophyll.
• Glucose is used as food for energy and growth.
• Oxygen is released as a byproduct into the atmosphere.

Last verified on 10-03-2026

Explanation

• A stretched spring possesses potential energy.
• When a spring is stretched or compressed, energy is stored in it.
• This stored energy is called elastic potential energy.
• It can be converted into kinetic energy when released.
• The more the stretch, the more energy is stored.

Last verified on 08-06-2026