Explanation

• During a physical change, the chemical composition of a substance does not change.
• Only the state, shape, or size may change.
• No new substance is formed.
• Examples include melting, freezing, and boiling.

Last verified on 25-06-2026

Explanation

• The instrument used to measure temperature is called a thermometer.
• A thermometer shows how hot or cold an object or place is.

Additional information:

• Barometer measures air pressure.
• Hygrometer measures humidity (moisture in air).

Last verified on 16-06-2026

Explanation

• Turning red litmus paper blue is NOT a property of acids; it is a property of bases.
• Acids turn blue litmus paper red.
• Acids generally have a sour taste, are often corrosive, and react with some metals to release hydrogen gas.
• Acids produce hydrogen ions (H⁺) in water.

Last verified on 25-06-2026

Explanation

• Black Gold: Petroleum (Crude Oil)
• Color: Dark black / brownish black
• Main Uses: Fuel, petrol, diesel, kerosene, plastics
• Importance: Backbone of modern industry and transport

Additional information:

• Top Oil-Producing Countries:
  1. Saudi Arabia
  2. USA
  3. Russia
  4. Iraq
  5. Iran

Last verified on 16-06-2026

Explanation

• Symbol: Hg
• Atomic number: 80
• Melting point: -38.83 °C
• Atomic mass: 200.59 u

Last verified on 13-03-2026