Chemistry

The compost producing pit should be kept covered so that flies cannot make entry into it and bad odour is minimized.
The waste materials which are non-biodegradable like glasses, plastic bags, plastic bottles, polybags, must be handed over to the vendors who can send them to the recycling plants.

Domestic waste can be separated into biodegradable and non-biodegradable materials. Non-biodegradable materials such as plastic, glass, metal scraps etc. are sent for recycling.  Biodegradable wastes can be deposited in landfills and are converted into compost to be used as manure.

Excessive phytoplankton (organic pollutants such as leaves, grass trash etc.) present in water are biodegradable. Bacteria decompose these organic matters in water. During this process, when a large number of bacteria decompose these organic matters, they consume the dissolved oxygen in water. When the level of dissolved oxygen falls below 6 ppm the fish cannot survive.

The solar energy radiated back from the Earth's surface is absorbed by the greenhouse gases (CO₂, CH₄, O₃, CFCs) present near the Earth's surface.
They heat up the atmosphere near the Earth's surface and keep it warm. As a result of these, there is the growth of vegetation which supports life. In the absence of this effect, there would be no life for both plants and animals on the surface of the Earth.

1.30 Knowing the density of an unknown metal and the dimension of the unit cell, the atomics mass of the metal can be determined.

Let, Atomic mass of element

(M)=d* a³* NA x Z

Where, d = density

• a³= volume of the unit cell
• NA = Avogadro's number
• Z= number of atoms present in one unit cell.
• Density of the unit cell= Mass of the unit cell / Volume of the unit cell
• d= zm / a³

Pesticides are the chemical compounds used to control the damage caused by pests (insects, rodents etc.)
Example: Aldrin, Dieldrin, B.H.C etc.
Herbicides are the chemicals used to control weeds.
Example: Triazines, Sodium chlorate (NaClO₃), sodium arsenite (Na₃AsO₃).

1.28 Coordination number is the number of the nearest neighbors with which a given atom is in contact. In an 
ionic crystal, the coordination number of an ion refers to the number of oppositely charged ions that 
surround that ion.
The coordination number of atoms in a
(a) Cubic close-packed structure is 12.
(b) Body-centred cubic structure is 8

The major sources of soil pollution are industrial wastes and agricultural pollutants like fertilizers and pesticides. Insecticides like DDT are insoluble in water and are absorbed by plant roots. Many pesticides like Aldrin and Dieldrin are toxic and non-biodegradable, which can enter the higher trophic levels through food chains, causing metabolic and physiological disorders. Industrial wastes comprise of several toxic metals such as Pb, As, Hg, Cd etc.

To control soil pollution, the addition of pollutants to the soil should be avoided. Waste materials should undergo proper treatment and recycling before dumping.