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

Explanation

• Diffusion is the natural movement of particles from an area of higher concentration to lower concentration without external force.
• It occurs in gases, liquids, and even solids to some extent.

Last verified on 14-10-2026

Explanation

• Aeroplanes fly in the troposphere.
• It is the lowest layer of the Earth's atmosphere.
• It extending up to about 12 km (7.5 miles) above the Earth's surface.
• The troposphere is where weather occurs, and it's the layer where aircraft operate.
• It typically cruising at altitudes between 30,000 to 40,000 feet (9,100 to 12,200 meters).

Additional information:

• Stratosphere: Contains the ozone layer.
• Mesosphere: Most meteors burn up here.
• Thermosphere: Includes much of the ionosphere and auroras.

Last verified on 12-10-2026

Explanation

• The electromagnetic force acts between electrically charged particles.
• It causes both attraction and repulsion between charged particles.
• It is responsible for electricity, magnetism, light, and chemical bonding between atoms.

Additional information:

• Gravitational force: Acts between objects with mass and energy.
• Strong nuclear force: Holds quarks together and helps bind atomic nuclei.
• Weak nuclear force: Responsible for processes such as beta radioactive decay.

Last verified on 12-10-2026

Explanation

• Centrifugation is a separation method that uses rapid rotation to separate components according to their density.
• Cream contains fat globules that are less dense than the watery part of milk.

Additional information:

• Distillation: Separates substances based on differences in boiling points.
• Sublimation: A solid changes directly into a gas.

Last verified on 12-10-2026

Explanation

• The modern periodic table arranges elements in order of increasing atomic number.
• The atomic number is the number of protons present in the nucleus of an atom.
• Elements with similar chemical properties are placed in the same group (vertical column).
• The modern periodic law was established by Henry Moseley.

Last verified on 12-10-2026