Explanation

• CFCs, carbon dioxide (CO₂), and methane (CH₄) are all greenhouse gases.
• Carbon dioxide traps heat in the atmosphere and increases temperature.
• Methane is a very strong greenhouse gas with high warming effect.
• CFCs also damage the ozone layer and act as greenhouse gases.

Last verified on 16-06-2026

Explanation

• The atmosphere is an open system.
• Because it exchanges both matter and energy with surroundings.
• Gases like oxygen, carbon dioxide, and water vapour continuously move in and out.
• Energy from the Sun enters and heat is also released back into space.
• This continuous exchange keeps atmospheric processes active.

Last verified on 16-06-2026

Explanation

• Nitrogen makes up about 78% of the Earth’s atmosphere.
• Oxygen is about 21%,
• Other gases like argon and carbon dioxide are in very small amounts.

Last updated by NA on 28April 2026

Explanation

• The ecosystem is the structural and functional unit of the environment.
• Ecosystem = Biotic + Abiotic components
• Biotic: plants, animals, microorganisms
• Abiotic: water, air, soil, sunlight

Last verified on 08-06-2026

Explanation

• Because sound is just vibrating air, space has no air to vibrate and therefore no sound in a vacuum.
• Sound waves below 20 Hz are known as infrasound.
• Sound waves above 20 kHz are known as ultrasound.

Sound waves transmit a medium such as a gas, liquid, or solid.

• The speed of sound in air is about 343 meters per second.
• The sound travels at 1,481 m/s in water.
• The speed of sound in a vacuum is zero meters per second.

Last verified on 07-06-2026