Explanation

The initial setting of cement is caused by:

• Hydration of Tricalcium Aluminate (C₃A).
• Reaction of C₃A with water, which starts rapidly after mixing.
• Formation of calcium aluminate hydrates, causing the paste to stiffen.
• Gypsum is added to slow down this reaction and prevent flash setting.

Explanation

Periscopes allow a submarine, when submerged at a relatively shallow depth, to search visually for nearby targets and threats on the surface of the water and in the air.

When not in use, a submarine's periscope retracts into the hull.

Explanation

Quantum numbers describe values of conserved quantities in the dynamics of a quantum system

Explanation

A protein is a naturally occurring, extremely complex substance that consists of amino acid residues joined by peptide bonds. Proteins are present in all living organisms and include many essential biological compounds such as enzymes, hormones, and antibodies.

Explanation

Explanation

Found in many foods including yeast, cereal grains, beans, nuts, and meat

Water soluble 

Explanation

Seismic waves are waves of energy that travel through Earth's layers

 result of  volcanic eruptions.

 large landslides and large man-made explosions that give out low-frequency acoustic energy.

Explanation

 Common salt comprises sodium and chlorine.

Sweat consists of about 99% water,

0.2-0.5% salts mainly sodium chloride

and traces of urea (0.08%).

Explanation

gibbous moon is the phase of the moon in which its illuminated part is greater than a semicircle and less than a circle.

Explanation

The epicenter of an earthquake is the point on the earth's surface vertically above the focus. Maximum damage is caused at the epicenter.

زلزلے کا مرکز زمین کی سطح پر عمودی طور پر اوپر کی حیثیت سے ایک نقطہ ہے۔ زیادہ تر نقصان زلزلے کے مرکز پر ہوتا ہے۔