Explanation

• The symbolic representation of a molecule of a compound is called a formula.
• It uses symbols and numbers to represent the composition of the molecule.
• For example, the formula for water is H₂O, indicating two hydrogen atoms and one oxygen atom.

Last verified on 15-03-2026

Explanation

• The filament of an electric bulb is made of Tungsten.
• Because it has a very high melting point (~3422°C).
• It can glow brightly without melting.
• Tungsten provides efficient and long-lasting light in incandescent bulbs.

Last verified on 15-03-2026

Explanation

• Baking soda releases carbon dioxide (CO₂) gas when it reacts with an acid or heat.
• The CO₂ bubbles expand in the batter, making it soft, fluffy, and porous during baking.
• Chemical formula of baking soda: NaHCO₃ (Sodium bicarbonate).

Last verified on 15-03-2026

Explanation

• A true solution is a homogeneous mixture in which the solute is completely dissolved in the solvent at the molecular level. 
• The particles are very small and cannot be seen with the naked eye. 
• True solutions are stable and do not settle down on standing.

Examples of true solutions (homogeneous mixtures):

• Salt in water (NaCl solution)
• Sugar in water
• Vinegar in water
• Alcohol in water
• Copper sulfate in water

Last verified on 15-03-2026

Explanation

• Valency is the combining capacity of an atom to form molecules or compounds.
• It depends on the number of electrons an atom can lose, gain, or share to complete its outer shell.

Last verified on 15-03-2026

Explanation

• Double Displacement Reaction: Two compounds exchange ions or radicals to form new compounds.
• General form: AB + CD → AD + CB.
• Example: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

Additional information:

• Decomposition: Single compound breaks into two or more simpler substances.
• Combination (Synthesis): Two or more substances combine to form one compound.

Last verified on 13-03-2026

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

• Conduction is the process of heat transfer through direct contact of molecules.
• In solids, especially metals, molecules vibrate and pass energy to neighboring molecules.
• No movement of the substance itself is required; only energy is transferred.

Last verified on 13-03-2026

Explanation

• Green plants use carbon dioxide (CO₂) from the atmosphere to make food via photosynthesis.
• In photosynthesis, CO₂ + H₂O → Glucose + O₂ (with sunlight and chlorophyll).

Last verified on 13-03-2026