Explanation

• Sublimation is the process in which a solid directly changes into a gas without passing through a liquid phase.
• This endothermic phase transition
• Occurs when a substance absorbs enough energy to overcome intermolecular forces.
• Deposition: Gas to Solid (the reverse process).
• Examples: Dry ice, iodine, frost/snow.

Explanation

• An ionic bond forms when one or more electrons are transferred from one atom to another.
• Ionic bond: Formed by electron transfer, e.g., sodium chloride (NaCl).

Additional information:

• Covalent bond: Formed when atoms share electron pairs, e.g., water (H₂O).
• Metallic bonding: Positive metal ions are held together by attraction to delocalized electrons.
• Coordinate (dative) bond: A covalent bond in which both shared electrons are donated by one atom.

Last verified on 15-10-2026

Explanation

• An atom is the smallest possible particle of an element that can combine to form new compounds.
• Atoms are the building blocks of matter, and they cannot be broken down into smaller particles.

Last verified on 15-03-2026

Explanation

• An alkene is an unsaturated hydrocarbon that contains at least one carbon–carbon double bond (C=C). 
• C₂H₄ — Ethene: An alkene with one carbon–carbon double bond.

Additional information:

• C₂H₆ — Ethane: An alkane containing only single bonds.
• C₂H₂ — Ethyne: An alkyne containing a carbon–carbon triple bond.

Last verified on 15-10-2026

Explanation

• Rusting of iron is a chemical change.
• Because iron reacts with oxygen and moisture to form rust (hydrated iron oxide).
• A new substance is formed, and the change cannot easily be reversed.
• Rusting is a slow oxidation process that occurs in the presence of oxygen and water.
• Other examples of chemical changes: Burning wood, cooking food, and digestion.

Last verified on 15-10-2026