Explanation

• A molecule is the smallest particle of a substance that retains its chemical properties.
• It is made of two or more atoms chemically bonded together.
• Examples of molecules: H₂O, O₂, CO₂, NH₃, CH₄.

Additional information:

• An atom is the smallest unit of an element.
• A compound is a substance formed when different elements combine chemically.

Last verified on 13-03-2026

Explanation

• Freezing is the process by which a liquid changes to a solid.
• It is the reverse of melting, which is the process by which a solid changes to a liquid.

Last verified on 13-03-2026

Explanation

• The Moon's surface gravity is about 1/6th as powerful or about 1.6 meters per second.
• The Moon's surface gravity is weaker because it is far less massive than Earth.
• A body's surface gravity is proportional to its mass, but inversely proportional to the square of its radius.

Last verified on 13-03-2026

Explanation

• The symbol ⁴₂He indicates helium has 2 protons (atomic number = 2) and mass number = 4.
• In a neutral atom, the number of electrons = protons, so helium has 2 electrons.

Last verified on 13-03-2026

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

• Liquids have no fixed shape but have a fixed volume.
• Particles are close together but can slide past each other, allowing the liquid to flow.

Additional information:

• Solid: Are tightly packed and stay in a fixed position
• Gas: Are widely spaced and move freely in any direction

Last verified on 13-03-2026

Explanation

• Mitochondria are known as the powerhouse of the cell.
• They are the site of cellular respiration, where glucose is converted into ATP (energy).
• Mitochondria have a double membrane and their own DNA and ribosomes.
• They provide energy for all cell activities.

Last verified on 13-03-2026

Explanation

• Albert Einstein received the Nobel Prize for his discovery of the Law of the photoelectric effect
• The 1921 prize was actually awarded in 1922.

Explanation

• Meteorologists are scientists who study the atmosphere and weather conditions.
• They forecast tornadoes, hurricanes, floods, and other weather events using satellites, radar, and computer models.
• Their work helps in early warning systems and disaster management.

Last verified on 12-03-2026

Explanation

• Wavelength is the distance between two successive crests or two successive troughs in a transverse wave.
• It represents one complete cycle of a wave.

Additional information:

• Symbol used: λ (Lambda)
• SI unit: meter (m)
• Wave formula: v = fλ
• Example wavelength values: 1 m, 0.5 m, 10 cm, 500 nm, 700 nm
• Visible light wavelength range: ~400 nm – 700 nm

Last verified on 12-03-2026