Explanation

• Endothermic reactions absorb heat from the surroundings (e.g., photosynthesis, melting ice).
• Exothermic reactions release heat to the surroundings (e.g., burning fuel, respiration).
• The key difference is heat flow direction between the system and environment.

Additional information:

• Endothermic → feels cold to touch
• Exothermic → feels hot to touch
• Examples help remember: Ice melting (endo), Fire burning (exo)

Last verified on 09-02-2026

Explanation

• Endothermic reactions absorb heat from the surroundings.

Examples:

• Photosynthesis → plants absorb sunlight to make glucose
• Melting of ice → absorbs heat to change solid → liquid
• Dissolving ammonium nitrate in water → absorbs heat, feels cold

Burning of fuel is exothermic, releasing heat and light.

Last verified on 09-02-2026

Explanation

• Chemical changes produce new substances with different properties.

Examples:

• Cooking of food → new substances formed
• Burning of paper → produces ash and gases
• Rusting of iron → iron reacts with oxygen to form rust

Melting of ice is a physical change, only changing state from solid to liquid, no new substance is formed.

Last verified on 09-02-2026

Explanation

• Examples: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn)
• Reason for Inactivity: Complete valence electron shell → chemically stable

Additional information:

• Rarely form compounds, mostly inert
• Used in lighting (Neon lights), welding (Argon), and as inert environments in laboratories

Last verified on 08-02-2026

Explanation

• Protium (¹H₁): 0 neutrons, 1 proton
• Deuterium (²H₁): 1 neutron, 1 proton
• Tritium (³H₁): 2 neutrons, 1 proton

All have 1 proton and 1 electron, differ only in neutron number

Last verified on 08-02-2026

Explanation

• Freezing water into ice shows matter can change from one state to another.
• Water (liquid) becomes ice (solid) without changing its chemical composition.
• This is a physical change.
• Matter retains its properties but changes form/shape.
• Similar examples: melting, evaporation, condensation.

Last verified on 07-02-2026

Explanation

• In a solution, the solute is the substance present in a smaller amount.
• It dissolves in the solvent to form a uniform mixture.
• The solvent is present in larger quantity.
• Examples: Salt in saltwater, sugar in tea.
• Solute can be solid, liquid, or gas.

Last verified on 07-02-2026

Explanation

• TLC (Thin Layer Chromatography) is a technique used to separate and identify compounds in a mixture.
• Uses a thin layer of adsorbent (like silica gel) on a plate.
• Compounds move at different rates when a solvent passes through.
• Simple, quick, and cost-effective method.

Last verified on 06-02-2026

Explanation

• Sound waves are mechanical waves and need a medium to travel.
  • They travel fastest in solids, slower in liquids, and slowest in gases.
  • Solid particles are closely packed, allowing rapid vibration transfer.

Last verified on 04-02-2026

Explanation

• Hydrogen bonding occurs when hydrogen is covalently bonded to highly electronegative atoms like O, N, or F.
• Present in water (H₂O), ammonia (NH₃), and hydrogen fluoride (HF).
• Responsible for high boiling points, surface tension, and solubility.

Last verified on 04-02-2026