Explanation

There are 3 main types of chemical bonds based on electron behavior.

1. Ionic bond → electrons are transferred (lost or gained).
2. Covalent bond → electrons are shared between atoms.
3. Metallic bond → electrons are delocalized (free-moving) in metals.

Last verified on 09-06-2026

Explanation

• Chemical energy is the energy stored in the bonds between atoms and molecules.
• It is released or absorbed during chemical reactions.
• Found in substances like food, fuel, and batteries.
• It is a form of potential energy stored in chemical bonds.
• It changes into other forms like heat or light when reactions occur.

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

• The chemical formula for water is H₂O.

Atomic masses:

• Hydrogen (H) = 1 amu each → 2 × 1 = 2 amu
• Oxygen (O) = 16 amu

Total molecular mass = 2 (from H) + 16 (from O) = 18 amu.

Last verified on 07-06-2026

Explanation

• The law that states mass can neither be created nor destroyed is the Law of Conservation of Mass.
• This law states that mass remains constant in a chemical reaction.
• Matter cannot be created or destroyed, only transformed.

Last verified on 02-04-2026

Explanation

• Copper (تانبا) is a good conductor of electricity.
• It allows electric current to flow easily.

Additional information:

• Metals are generally good conductors.
• Non-metals usually do not conduct electricity.
• Good Conductors: Copper, Silver, Gold, Aluminum, Graphite
• Bad Conductors: Plastic, Rubber, Wood, Glass, Air

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

• Lyman series lies in the ultraviolet (UV) region of hydrogen spectrum.
• It is produced when an electron falls to the first energy level (n = 1).
• These transitions release high-energy photons.

Additional information:

• Balmer series lies in the visible region.
• Paschen and Brackett are in infrared.

Last verified on 05-06-2026

Explanation

Look at the reaction: N₂ + 3H₂ → 2NH₃

For every 1 N₂ that reacts, 3 H₂ react.  

So H₂ gets used 3 times faster than N₂.

Given: H₂ is used at 1.72 mol L⁻¹ h⁻¹  

Then N₂ is used 3x slower:

Rate of N₂ = 1.72 ÷ 3 = 0.57 mol L⁻¹ h⁻¹

Last verified on 05-06-2026