Everyday Science Mixed Quiz: WBPSC Clerkship GS Practice, 20 Questions

Vitamin A is needed to make the light-sensitive pigment in the retina. Without it a person cannot see in dim light, which is called night blindness. Lack of vitamin C causes scurvy and lack of vitamin D causes rickets.

Normal body temperature is about 37°C, equal to 98.6°F. 36.5°F is close to freezing and impossible for a living person. A temperature of 40°C counts as a high fever.

Diamond is an allotrope of carbon in which each atom is firmly bonded to four others, so it is the hardest natural substance. Graphite is also carbon, but its layers slide easily, so it is soft.

Sound is a mechanical wave and needs a solid, liquid or gaseous medium. A vacuum has no medium, so sound cannot travel through it. Sound actually moves faster in solids and liquids than in air.

Common salt is sodium chloride, NaCl. KCl is potassium chloride, CaCO3 is the main part of limestone and marble, and NaOH is caustic soda.

Red cells of O negative blood carry no A, B or Rh antigen, so in an emergency they can be given to patients of almost any group. AB positive is the universal recipient, since such people have no anti-A or anti-B antibodies.

When iron meets oxygen and moisture it is oxidised into a reddish-brown layer of iron oxide, called rust. It does not rust in dry air or in water without oxygen. That is why iron is painted, galvanised or oiled.

The SI unit of force is the newton (N): the force that gives a 1 kg mass an acceleration of 1 metre per second squared. The joule measures work or energy, the watt power and the pascal pressure.

Insulin is made in the beta cells of the pancreas and helps lower blood glucose. Too little insulin, or its failure to act, causes diabetes mellitus. The liver makes bile and the kidneys filter the blood.

Hydrogen has atomic number 1 and is the lightest element and gas. Helium is second lightest, but it is non-flammable, so balloons use helium for safety. Hydrogen is flammable.

A convex mirror always gives an erect, diminished image and has a wide field of view, so the driver sees a large area behind. A concave mirror magnifies near objects, so it is used for shaving mirrors and torches.

Vitamin C (ascorbic acid) is needed to make collagen. Without it the gums swell and bleed and wounds heal slowly, which is called scurvy. Lemon, amla, orange and guava are good sources.

On the pH scale 7 is neutral. Pure water is neither acidic nor basic, so its pH is 7. Below 7 a solution is acidic and above 7 it is basic.

Haemoglobin is the protein of red blood cells that carries oxygen from the lungs, and it needs iron to be made. Lack of iron lowers haemoglobin and causes anaemia. Lack of iodine causes goitre, and lack of calcium weakens bones.

Lightning and thunder occur together, but light travels at about 300,000 km per second while sound in air travels at about 340 m per second. So the light arrives almost instantly and the sound takes time.

About 78% of dry air is nitrogen. Oxygen is about 21%, argon about 0.93% and carbon dioxide only about 0.04%. Many people pick oxygen because animals need it to breathe.

Dry ice is solid carbon dioxide. It does not melt into a liquid but turns straight into gas at about −78.5°C, which is called sublimation. That is why it keeps things cold without making them wet.

An adult has 206 bones. A newborn has about 300, and as the child grows some of them fuse, bringing the number down to 206. The smallest bone is the stapes in the ear.

Citric acid is found in lemons and oranges, which is why they are called citrus fruits. Acetic acid is in vinegar, lactic acid in sour curd and formic acid in ant stings.