Explanation

• The branch of chemistry that studies heat energy released or absorbed during chemical reactions is called Thermochemistry.
• It explains how heat changes occur during reactions such as combustion, neutralization, and dissolution.
• It deals with concepts like enthalpy change (ΔH), exothermic reactions, and endothermic reactions.

Last verified on 11-03-2026

Explanation

• The formation of hydrogen and oxygen from water, which is an example of a decomposition reaction: 2H2O → 2H2 + O2
• In this reaction, water (H2O) decomposes into hydrogen (H2) and oxygen (O2).

Last verified on 11-03-2026

Explanation

• A Telescope is an optical instrument used to observe distant objects such as stars, planets, and galaxies.
• It collects and magnifies light or other forms of electromagnetic radiation.
• The term “telescope” was coined in 1611 by the Greek mathematician Giovanni Demisiani.

Last verified on 10-03-2026

Explanation

• When water cools from 4°C to 0°C, it expands as it freezes into ice.
• Unlike most substances, water’s maximum density is at 4°C; below this temperature, the volume increases and density decreases.
• This is why ice floats on water.

Last verified on 10-03-2026

Explanation

• Combustion is a chemical reaction in which a substance reacts rapidly with oxygen to produce heat and light.
• Commonly observed when wood, coal, or fuel burns.
• Combustion is an exothermic reaction because it releases energy.

Last verified on 10-03-2026

Explanation

• Antoine Lavoisier, a French chemist, is credited with discovering the law of conservation of mass in 1789 (1785).
• He demonstrated that matter cannot be created or destroyed in a chemical reaction, only transformed from one substance to another.

Last verified on 10-03-2026

Explanation

• Chlorofluorocarbons (CFCs) are chemical compounds used in refrigerators, air conditioners, and aerosol sprays.
• When released into the atmosphere, CFCs destroy the ozone layer by breaking down O₃ molecules.
• The ozone layer protects Earth from harmful ultraviolet (UV) radiation.

Last verified on 10-03-2026

Explanation

• Mitosis is the process by which a single cell divides to produce two identical daughter cells.
• It is essential for growth, tissue repair, and development in multicellular organisms.
• Mitosis maintains the same number of chromosomes in each new cell.

Additional information:

• Meiosis is different; it occurs in sex cells and reduces chromosome number by half.

Last verified on 10-03-2026

Explanation

• The stomach is an organ involved in digestion, not waste elimination.

1. Lungs: remove carbon dioxide through exhalation
2. Kidneys: filter waste and excess substances from the blood, producing urine
3. Skin: removes waste through sweating
4. Liver: detoxifies harmful substances and aids in their removal

Last verified on 10-03-2026

Explanation

• Car brakes are typically hydraulic systems, not pneumatic systems.

The examples of pneumatic systems:

• Spray gun: uses compressed air to atomize and spray paint or other materials.
• Bicycle pump: uses compressed air to inflate tires.
• Vacuum cleaner: uses compressed air to create suction and lift dust and debris.

Last verified on 09-03-2026