Explanation

• Air pressure decreases as altitude increases.
• At higher altitudes, there is less air above us.
• Therefore, the weight of the air column is lower.
• Air becomes less dense at higher altitudes.
• So, higher altitude = lower air pressure.

Explanation

• Life can't sustain itself without water
• It is needed for important biological processes.
• Plants require water for photosynthesis.
• Animals need water for survival and body functions.

Explanation

• Fluorine is the most electronegative element (3.98 on the Pauling scale).
• 7 valence electrons (2s² 2p⁵); needs one more for a stable noble gas configuration
• Small atomic radius → strong pull on bonding electrons
• High effective nuclear charge

Explanation

• An amphoteric substance can act as either an acid or a base depending on the chemical reaction it is involved in.
• The word "amphoteric" comes from the Greek word "amphi," meaning "both". 

Explanation

Reduction:

• Gain electrons
• Oxidation state lowers
• Always paired with oxidation (redox)
• Oxidizing agent gets reduced

Additional information 

Oxidation is the chemical process of:

• Losing electrons
• Oxidation state increases
• Always paired with reduction (together form redox)
• Reducing agent gets oxidized (it gives up the electrons)

Explanation

• Across a period: Ionization energy increases (stronger nuclear charge).
• Down a group: Ionization energy decreases (electron shielding + distance).
• Exceptions within a period:
  • Group 13: slight dip (new p subshell).
  • Group 16: slight dip (electron pairing repulsion).

Explanation

• Conduction: Heat transfer through direct contact between particles.
• Convection: Heat transfer through the movement of liquids or gases.
• Radiation: Heat transfer through electromagnetic waves.
• The Sun heats the Earth by radiation.
• Heat naturally moves from a hotter body to a colder body.

Explanation

The law is Newton's Law of Universal Gravitation.

• It states that gravitational force is directly proportional to the product of two masses.
• It is inversely proportional to the square of the distance between them.
• Formula: F = Gx m_1m_2/r^2
• G is the universal gravitational constant.
• The force acts between any two masses.

Explanation

• The mole (mol) is the SI unit for the amount of substance.
• 1 mol = 6.022 × 10²³ elementary entities (Avogadro's number)
• One of the 7 base SI units (adopted 1971)
• Applies to atoms, molecules, ions, etc.
• Redefined in 2019 (based on fixed Avogadro constant)
• Links microscopic particles to grams via molar mass.

Explanation

"6.022 × 10²³ atoms of carbon"

Each CO₂ molecule contains 1 carbon atom

So, 1 mole of CO₂ has 6.022 × 10²³ carbon atoms