Gypsum is added in the cement because:
> To slow the initial setting of cement when water is added.
> It is easier to work with slow setting cement.
> Such cement leads to its greater hardening.

The mixture cement, sand, water and gravel having an iron framework inside it is called RCC (Reinforced cement concrete).
It is used for:
> Construction of buildings, bridges, dams, etc.
> Making the fences, roofs, etc.

Glass is metallic silicate of various metals which is hard, transparent, amorphous and supercooled liquid that is prepared by heating a mixture of silica, sodium carbonate and calcium carbonate in a furnace,
Water glass is made by heating silica with sodium carbonate or potassium carbonate about 800c and cooling the product.
It is called water glass because it dissolve in water and it is also fire proof.

The materials used to make glass are listed below:
> Mixture of silica: 25%
> Pieces of glass: 25%
> Sodium carbonate:15%
> Calcium carbonate: 10%

Quartz glass is a pure crystalline glass which is prepared by heating silica at about 1600c and then cooling the products.

The homogenous mixture of sodium silicate, calcium silicate and boron silicate is called borosilicate (Pyrex) glass.
It is used for making laboratory apparatus like test tubes, flasks, breakers, ampules and other pharmaceutical containers.
Its characteristics are:
> It is hard and does not melt at ordinary temperature.
> It is strong than ordinary glass.
> It is more resistant to heat and chemical.

The homogenous mixture of potassium silicate and lead silicate is called lead crystal glass.
It is used or making lens, prisms, electric bulbs, TV screens, etc.
Its characteristics are:
> It has a high refractive index.
> It has the presence of lead silica.

Colored glass is prepared by adding certain metal oxides to the molten mass during the preparation of glass. Certain metal oxides impart a particular color to the glass. So, the selection of the metal oxide depends on the color of our choice.

Ceramics is a type of clay which contains the compounds of carbon, hydrogen, nitrogen, oxygen and silica.
It is produced by hydrated alumina silica. It contains other substance like limestone, magnesium carbonate, oxides of magnesia and iron.

Ceramic utensils are brought to use because:
> It is insulator of heat and electricity.
> It can resist high temperature.
> It has resistant to the actions of chemicals.
> It is hard and brittle.

Fibers are the thread like structure which is long, strong and elastic that are used to make ropes, clothes, nets, etc.
Naturally occurring fibers are called natural fibers. They are used for making clothes. They are of two types i.e plant fibers and animal fibers. Plant fibers are obtained from plants and are used for making sacks, bags, ropes, etc. And animal fibers are obtained from animals and are used for making different types of clothes.

The fibers which are made artificially by chemical process are called synthetic fibers.
Its characteristics are listed below:
- It is strong and elastic fiber.
- It doesn't wrinkle.
- It absorb less water and dries up easily.
- It has low melting point.
Its advantages are listed below:
- It is used to make clothes.
- It retain their creases.
- They are not attacked by insects.
- They are dried up easily.
- They are light.

A polymer is a very large and complex molecule formed by the combination of many simple and small molecules.
The two types of polymers are:
- Natural polymers: wool, silk, natural rubber, etc.
- Synthetic polymers: polythene, nylon, artificial rubbers, etc.

The process by which a large number of simple monomers are combined to give a polymer is called polymerization.

Plastics are the artificial materials made by the polymerizationof carbon containingmonomers like ethene, vinyl, etc.
Plasticsmaterials areused more than other materials because:
-They are cheapen, lighter and stronger.
-They are available in different shapes, sizes and colors.
-They can be recycled and remoldedintoanydesiredshapes.
-They aredurable and are insulator.

Bakelite are the thermo-setting plastics formed by thecondensation and polymerization of formaldehyde andcarbolic acid (Phenol).
Its uses are:
-It is used to make the handles of cooking utensils.
-It is used to make water tanks.
-It used to make the electrical fittings.
-It is used to make the covers of different devices.

A cleaning agent prepared by heating fat or oilwith sodium hydroxide.
The raw materials required formaking soap are:
-Vegetable oil of olive, coconut, cotton seeds.
-Sodium hydroxide.

Sodium chloride increases the ionic product and decreasesthe solubility products and sodium carbonate make thesoap hard. So, they are used in soap.

The process by which soap is prepared is calledsaporification. During saporification, sodium chloride isadded in solution to increase the ironic products and decreasethesolubility of the products. Soap having less densityfloats on the surface of the solution which are collectedand kept into moulds to get soap cake. After,sodiumcarbonate is added to make thesoaphard.

Detergents are one of the cheap and popular cleansingagents made from hydrocarbons of petroleumby-products.
Detergents are called soapless soup because it hascleansing property like that of soap but doesn't containsanychemicals that are found in soap.

The artificial poisonous chemicals compounds that are used to kill or control harmful insect are calledinsecticides.
The effects that are seen due to excessive use ofpesticidesare:
-Eco-balance is being disturbed.
- Friendly insects are also dying along with rivalinsects.
-Air pollution.
-Health problems and mutation.
-Environment degradation.

DDT : Dichloro diphenyol trichloro ethane

BHC: Benzene hexacloride

PVC: Poly vinyl chloride

RCC: Reinforced Cement Concrete

Compost manure is an organic fertilizer which ismade from dead, decayed and decomposed parts ofanimals and plants or other wasteproducts.
It is prepared by mixtureof dead plants, animalsor their wasteproducts are kept in a pit with alteringlayers of soil. Due to microbialaction, the mixture getsdecomposed into compost manure.

The fertilizer which supply all the basic nutrients, i.enitrogen, phosphorus and potassium are
called NPK fertilizers.
It is called a complete fertilizer because they aremade by mixing too or more than two single fertilizerswhich has sufficient amount of allrequired nutrients for the growth and development of plants.

The function of NPK in plants are:
-It is essential for rapid growth and high yelding.
-It helps in formation of protein, chlorophyll, etc. inplants.
-It helps in ripening fruits anddevelopment of seeds.
-It helps to resist diseases.
-It helps in photosynthesisand growth of flowers.
-It helps in protein synthesis, cell division, etc.

Due to the deficiency of nitrogen, leaves becomeyellow, flower don't bloomproperly.
Due to the deficiency of phosphorus, plants are notable to resist their diseases.
Due to the deficiency of potassium, leaves and budswither and immunity is reduced.

We know, nitrogen is an essential nutrients thatacceleratesthe growthand development of plants as it issensitizedby the plants. The aquatic plants cana can use up the nitrogen of nitrogenous fertilizerforits growth, but aquatic animals cannot. In the otherhand, this fertilizer reacts with oxygen available inthe water and create an oxygen deficiency in water.So, aquatic animals diedue to the lack of oxygen. Therefore,nitrogen fertilizer increase the growth of aquaticplantsbut decreases the ...

Followingare the adverse effects of DDT:
-It cause air, water and soil pollution.
-Cover of bird's egg becomes thin and weak.
-It cause animals lung diseases.
-It reduces the rate of photosynthesis of plants.
-It reduce the rate of transpiration of plants.

We know that, lead crystal glass shows anextraordinarysparkle as it has a high refractive index.So, it is used for making expensive glassware.

We know, bakelite is insulator of heat and doesn't meltsat high temperature also but PVC melts on simpleheating also. So, PVC isn't used to cover the handleofpressure cookers but bakelite is.

We know, plastics are the light and strong compoundthat doesn't decay or decompose in the nature forlong time. Theoveruse of plastics in increasing the amountof plastics in the world. These all plastics are thrown inthe land after use which cause land pollution. Notonlythis but also, it remains in land for many years thatdegradesthe quality of soil and creates disorder ineco-system. So, environmentalist are calling to shun theuse of plastics.

Soaps not suitable for washing clothes with hardwater because hard water having large amounts ofcalcium and magnesium ions give insoluble precipitate.

Detergent are used more than soap because ithave stronger cleansing action than that of soap.It can be used even with hard water but soapis insolublein it and its prepared from hydrocarbonas petroleum by-products.So, it is used more thansoap as its cheaper also.

a.Hard glass and soft glass.

b.Thermosetting and Thermo plastics.

The pollution created by unwanted and excessive useof chemical substances is called chemicalpollution.
Its major causes are:
- Excessive use of insecticides & fertilizers.
-Household wastes and plastics.
-Mismanagement of industrial wastes.
-Lack of public awareness.

Following things should be done to control chemicalpollution:
-RPG and unmanaged urbanization should be controlled.
-Solid and liquid waste should be managed properly.
-Industrial and residental area should be separated.
-Awareness programs about chemicalpollution, its effectsand solution measures should be conducted.

Any three ways to get rid of chemical pollution are:
- We should use chemical fertilizers in proportionateamount after testing soil.
- Household and industrial wastes should be managedwell.
-We should be careful while using Insecticidesand pesticides.
-Control of RPG and healthy settlement.

The solid wastes that decays and decompose due toaction of microorganism & called bio-degradablewastes.
The wastesthat doesn't decay and decompose inthe nature due to the actions of microorganism is callednon-biodegradable wastes.

Solid waste management refers to the management ofwastes through the collection, transport, processing andreusing of wastes materials. 3R in the popular methodologyof solid waste management. Not only the environment isdegraded but also the various communicable diseasesspreadsif the wastes are not managed or disposedproperly.Hence, these wastes should be managed properly andcarefully. Therefore, SWM plays an important role ineco-balance and for the sustainable preservation ofthe environment

The method of burning solid wastes at very hightemperature is called incineration. It is doneat wastedumping site.