Biology : Question and answer / Written by Anjali De nandee

Biology Question and answer

By Anjali Denandee.

Date: 18-08-2019 (Delhi)

  1. Why is it easy to recycle plastic and metal? 

Plastic: Used plastics are readily available in the market as industrial waste which can easily be recycled by melting and molding.  It requires mixing fresh plastic material with macromolecular welding flux during the process of recycling to avoid phase separation.

Metal: Recycling of metal from scrap metal is easier as it consumes less energy and also conserves natural resources by reducing greenhouse gas emissions as compared to production of new metal from virgin ore. It also saves water uses and also very less mining wastes.

  1. Sand contains the elements.

Composition of Sand varies depending on the source and climatic condition. It is in granular form finer than gravel and coarser than silt. The most common constituents of sand is Silica (Silicon dioxide, or SiO2), in the form of quartz. The other most common constituent of sand is Calcium Carbonate, such as Aragonite. This has been created by natural decay of the shell of Shellfish and Coral bodies (Reef), over the past million of years.

  1. Why does ice float on water?

According to Archimedes’ principle-For an object to float on water, it must displace an equal amount of water. Most of the substances are denser when in their solid (Frozen) states. But in case of water when it freezes into ice, it becomes less dense because of Hydrogen bonding. The heavier water displaces the lighter ice, so the ice floats on the top of water.

  1. Mention the receptors for light and sound in animals.

Photoreceptor: It is the light receptor in animal body.  This sense organ is capable of responding to light stimulus. Photoreceptors are of different degrees of perfection and vary from animal to animal.

Phonoreceptor: It is the sound receptor in an animal. Phonoreceptor i.e. sense of hearing can detect sounds caused by outside disturbances at some distance from the body.  Powers of Phonoreceptor vary from animal to animal.

  1. What is an epicenter?

According to seismology, the epicenter is the point on Earth’s surface directly above a hypocenter. It is the point where an earthquake or any underground explosion originates. The distance to quake’s epicenter can be calculated by a Geologist and this distance is called the epicentral distance. The instrument by which the earthquake is measured is called Seismometer. These are of two types- Seismic magnitude scales and Seismic intensity scales. According to seismology earthquake is measured in ° (Degrees) and also it is denoted as Δ (Delta).

  1. Name two hard and two soft objects.

Name of two hard objects are Brick and Wood.

Name of two soft objects are Cotton and Feather.

  1. Write the full form CNG, LPG and PNG.

CNG: Compressed Natural Gas.

LPG: Liquefied Petroleum Gas.

PNG: Pipelined Natural Gas.

  1.   Why do stainless steel utensils not rust on exposure to air?

Stainless steel utensils not rust on exposure to air because it is not just an alloy of Iron, Carbon and Chromium. Manganese is also used in the alloy. In some cases Nickel and Molybdenum are also added to make it rust proof. If Aluminum corrodes, then the layer of aluminum oxide can protect it from further exposure to oxygen molecules and it prevents from further corrosion that is the cause of not rust.

  1. Why does the milk that comes in packets not spoil?

Packet milk are not spoiled because they are Pasteurized and then packed. Pasteurization done by heating milk at 72.5 degree to kill all bacteria that are harmful and cooling it immediately to less than 5 degree centigrade. It can remain in good condition for 48 hours if kept in refrigerated condition.

  1. Name two industries near the Taj Mahal causing air pollution?

Petha(Translucent soft candy ) Industries.

Glass bottle manufacturing industries.

These two industries near Taj Mahal is causing air pollution.

  1. Who unified celestial and terrestrial mechanics?

Sir Issac Newton unified the celestial and terrestrial mechanics.

  1. During photocatalysis to split water, hydrogen and oxygen form in the same chamber. Is it true or false?


Hydrogen and Oxygen is formed in two different chambers. The ratio of Hydrogen and Oxygen is 2:1.  Formation of these, in same chamber would again form water or hydrogen peroxide or any other compound.


  1. A flat plate collector typically does not need to track the sun across seasons since it is flat.


Flat plate collectors are capable of absorbing the diffuse radiations of the sun and they need not to track the sun throughout the seasons.

  1. If more water molecules are present in the atmosphere the sky looks.

If more water molecules are present in the atmosphere the sky looks blue. The sky is originally colorless. It seems blue because of presence of dust and water particles in the surrounding which scatters the blue light. Sunlight contains seven colors. Due to this reason when we can see rainbow appearing after raining and the sky appears blue due to presence of water.

  1. Is salt is carbon compound used in daily life?


The salt used in daily life is not a carbon compound. The common edible salt we use in daily life is Sodium Chloride (NaCl). Na stands for Sodium and Cl stands for Chlorine. Symbol of Carbon is C. So the Carbon is not in NaCl.

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