Explanation

• An electron carries a negative electric charge.
• Its charge is approximately −1.602 × 10⁻¹⁹ C.
• A proton has an equal magnitude of positive charge, while a neutron has zero electric charge.
• The charge of an electron is called the elementary charge with a negative sign.

Explanation

• The ozone layer protects the Earth from the sun.
• It is a part of the atmosphere that absorbs most of the harmful ultraviolet light from the sun.
• It sits in the stratosphere.
• It is about 9 to 18 miles above the Earth.
• It stops dangerous UV rays from hurting living things.

Last updated by NS on 14-8-2026

Explanation

• Intermediate-focus earthquakes: occur at depths of 70–300 km.

Additional information:

• Shallow-focus earthquakes: occur at depths of 0–70 km.
• Deep-focus earthquakes: occur at depths of 300–700 km.

Last verified on 22-10-2026

Explanation

• Excretion is the biological process by which waste products are removed from the body.
• The kidneys remove urea, excess water, and salts through urine.
• The lungs remove carbon dioxide and some water vapour during exhalation.
• The skin eliminates small amounts of water and salts through sweat.
• Excretion helps maintain the body's internal balance, known as homeostasis.

Last verified on 22-10-2026

Explanation

Oxidation is the chemical process of:

• Losing electrons
• Oxidation state increases
• Always paired with reduction (together form redox)
• Reducing agent gets oxidized (it gives up the electrons)

Additional information 

Reduction:

• Gain electrons
• Oxidation state lowers
• Always paired with oxidation (redox)
• Oxidizing agent gets reduced

Last verified on 22-10-2026

Explanation

• Carbohydrates are the fastest and main source of energy.
• They are quickly converted into glucose in the body.
• Glucose is used immediately for energy production.
• They provide instant fuel for brain and muscles.

Last verified on 14-05-2026

Explanation

• Guava is rich in vitamin C, which improves the absorption of non-haem iron found in cereals, pulses, and other plant foods.
• Tea contains polyphenols that can reduce iron absorption when consumed with meals.
• Postponing tea until about 1–2 hours after the meal can help reduce its inhibitory effect on iron absorption.
• Combining vitamin C-rich foods, such as guava, citrus fruits, or tomatoes, with plant-based meals is a practical way to improve iron availability.

Last verified on 21-10-2026

Explanation

• A composite liner acts as a barrier that reduces the movement of contaminated liquid into the surrounding soil and groundwater.
• A leachate collection system collects polluted liquid produced when water passes through waste, allowing it to be treated safely.
• Methane capture collects gas released during the decomposition of biodegradable waste.
• Methane is a powerful greenhouse gas that contributes to global warming.
• Captured methane can be flared or used to generate energy, reducing its direct release into the atmosphere.

Last verified on 21-10-2026

Explanation

• Arsenic is a toxic substance that can contaminate groundwater and cause serious health problems after prolonged exposure.
• Water sources confirmed to have excessive arsenic should be clearly marked, and people should be advised not to use them for drinking or cooking.

Last verified on 21-10-2026

Explanation

• Nitrogen (N₂) makes up about 78% of Earth's atmosphere. 
• It is generally not considered an air pollutant in its normal form.

Additional information:

• Hydrocarbons can contribute to air pollution by reacting with nitrogen oxides to form ground-level ozone.
• Chromium, especially certain compounds such as hexavalent chromium, can pollute the air and pose serious health risks.
• Carbon dioxide (CO₂) is a greenhouse gas that contributes to global warming and is also classified as an air pollutant in some environmental frameworks.

Last verified on 21-10-2026