Explanation

• The incorrect statement is: States of matter does not change during chemical reactions.
• During chemical reactions, states of matter can change.
• For example, a solid may dissolve in a liquid, a liquid may vaporize, or a gas may condense into a liquid.

Last verified on 09-03-2026

Explanation

• Pressure is a fundamental physical quantity that is defined as the force exerted per unit area.
• It is a measure of the strength of a force acting on a surface.
• It is typically measured in units such as Pascals (Pa) or pounds per square inch (PSI).

Last verified on 10-02-2026

Explanation

A nucleotide, the building block of DNA and RNA.

It consists of three components:

1. A phosphate group (phosphate)
2. A sugar molecule (deoxyribose in DNA and ribose in RNA)
3. One of four nitrogenous bases (Adenine, Guanine, Cytosine, and Thymine in DNA; Adenine, Guanine, Cytosine, and Uracil in RNA)

Last verified on 07-02-2026

Explanation

• Uracil (U) is not a base found in DNA.
• Instead, it is found in RNA (ribonucleic acid), where it replaces Thymine (T).

The four organic bases found in DNA are:

1. Adenine (A)
2. Cytosine (C)
3. Thymine (T)
4. Guanine (G)

Last verified on 03-02-2026

Explanation

Chromosomes are made up of:

• Nucleic acid (DNA or RNA)
• Proteins (histones and non-histone proteins)

A chromosome is made up of proteins and DNA organized into genes.

Each cell normally contains 23 pairs of chromosomes.

Explanation

• The SI unit of energy is the Joule (J).
• It is the unit of energy, work, and heat.

Additional information:

• 1 Joule (J) = 1 Newton × 1 meter
• Calorie – 1 cal = 4.184 J
• Kilowatt-hour (kWh) – 1 kWh = 3.6 × 10⁶ J
• Electronvolt (eV) – 1 eV ≈ 1.602 × 10⁻¹⁹ J
• Erg (CGS unit) – 1 erg = 10⁻⁷ J

Last verified on 17-01-2026

Explanation

• Main Cause: Freon / CFCs
• Effect: Breaks down O₃ molecules → more UV-B radiation
• Other Contributors: Halons, carbon tetrachloride
• Result: Skin cancer, cataracts, climate impact

• The Montreal Protocol (1987) aimed to reduce CFC emissions
• Ozone layer protects Earth from harmful ultraviolet rays

Explanation

Water has maximum density at 4°C.

When Water is in its Solid form (Ice) below 0°C.

Explanation

• Carbon dioxide (CO2) is a major greenhouse gas.
• It responsible for about 65% of the Earth's greenhouse effect.

Explanation

• Fission is the splitting of a nucleus that releases free neutrons and lighter nuclei.
• The fission of heavy elements is highly exothermic which releases about 200 million eV compared to burning coal which only gives a few eV.