Weeding is the process of controlling the growth of weeds. There are various methods of weeding:

• Spraying weedicides on the weeds
• Manually plucking the weeds by hands
• Removing weeds by trowel and harrow
• Ploughing the field to remove the weeds even before sowing the seeds

The process of loosening and turning the soil is called ploughing (tilling). It is done by using an implement called plough. Ploughs are made of wood or iron having an iron tip for easy penetration into the soil. The ploughs are pulled by a pair of bullocks or by a tractor.

Advantages of ploughing:

1. The loose soil allows the plant roots to penetrate freely and deeper into the soil so that plants are held more firmly to the ground.
2. The loose soil allows the roots of the plants to breathe easily.
3. The loose soil helps in the growth of worms and microbes present in the soil as they help in turning and loosening of soil.
4. Ploughing also uproots and buries the weeds standing in the field and thereby suffocates them to death.
5. The loosening and turning of soil during ploughing brings the nutrient rich soil to the top so that the plants can use these nutrients.

Few diseases caused by bacteria are:

(i) Tuberculosis (T.B.) – T.B. is an infectious disease which is communicated from one person to another directly or indirectly. It is caused by  bacterium called Mycobacterium tuberculosis. T.B. can affect all parts of the body such as lungs, lymph glands, bones, intestine etc.

(ii) Cholera – Cholera is an acutely infectious, fatal disease and is more common during overcrowded fairs, festivals and after floods. Cholera is caused by the bacterium Vibrio Cholerae. It is transmitted by flies, contaminated water and food.

(iii) Typhoid – Typhoid is most common communicable disease in India. Typhoid fever is common in humans of the age 1to 15 years age group. Typhoid is caused by a rod-shaped and motile bacterium, called Salmonella typhi which is commonly found in the intestine of human beings. Human infection is direct.

(iv) Diarrhoea – Diarrhoea is an abnormally frequent discharge of semisolid or fluid faeces. The diarrhoea spreads through infection by contaminated food, water, drinks, hands, clothes, etc. The causative agents of diarrhoea are mainly bacteria such as Escherichia coli, Clostridium botulinum, Shigella dysentiriae, Campylobacter jejuri and Salmonella.

Few diseases caused by bacteria are:

(i) Tuberculosis (T.B.) – T.B. is an infectious disease which is communicated from one person to another directly or indirectly. It is caused by  bacterium called Mycobacterium tuberculosis. T.B. can affect all parts of the body such as lungs, lymph glands, bones, intestine etc.

(ii) Cholera – Cholera is an acutely infectious, fatal disease and is more common during overcrowded fairs, festivals and after floods. Cholera is caused by the bacterium Vibrio Cholerae. It is transmitted by flies, contaminated water and food.

(iii) Typhoid – Typhoid is most common communicable disease in India. Typhoid fever is common in humans of the age 1to 15 years age group. Typhoid is caused by a rod-shaped and motile bacterium, called Salmonella typhi which is commonly found in the intestine of human beings. Human infection is direct.

(iv) Diarrhoea – Diarrhoea is an abnormally frequent discharge of semisolid or fluid faeces. The diarrhoea spreads through infection by contaminated food, water, drinks, hands, clothes, etc. The causative agents of diarrhoea are mainly bacteria such as Escherichia coli, Clostridium botulinum, Shigella dysentiriae, Campylobacter jejuri and Salmonella.

Plastics are non-corrosive in nature, they do not react even if they come in contact with strong chemicals. For example, the cleaning chemicals that we use at home are stored in plastic bottles, instead of metal containers. Plastics are non-corrosive in nature as: (i) they do not react with any substances. (ii) plastics do not react with air and water which are essential for corrosion.  All the above mentioned properties make plastic useful for storage of various kinds of materials, including chemicals.

The various tasks performed by a farmer to produce a good crop are called agricultural practices. The various agricultural practices which are carried out at various stages of crop production are:

1. Preparation of soil
2. Sowing
3. Adding manure and fertilisers
4. Irrigation
5. Removal of weeds
6. Harvesting
7. Storage of food grains.

Manure is the decomposed form of dead plants and animals which is applied to the soil to increase the production. It is a natural form of fertilizer and is cost-effective. The human and animal excreta is also used as manure. The livestock manure is rich in nitrogen, phosphorus, and potassium.

Acrylic is made from Acrylonitrile, a colorless flammable liquid that is derived from polypropylene plastic. It is combined with other chemicals and placed into a spinning solution. The mixture is then either injected into air-filled space and dry spun or sprayed into water and wet spun. Acrylic is lightweight, soft, and warm, with a wool-like feel. It can also be made to mimic other fibers, such as cotton when spun on short staple equipment. Some acrylic is used in clothing as a less expensive alternative to cashmere, due to the similar feeling of the materials.

Threshing is the process of loosening the edible part of grain (or other crop) from the husks and straw to which it is attached. Threshing does not remove the bran from the grain. Threshing may be done by beating the grain using a flail on a threshing floor. For examples; pebbles, broken grains and insects are separated from rice, wheat and pulses; by handpicking. Threshing: Threshing is used for separating seeds from the harvested stalks. Manual Threshing: When the quantity is small, threshing is done manually.

Animal husbandry refers to livestock raising and selective breeding. It is the management and care of animals in which the genetic qualities and behavior of animals are further developed for profit. A large number of farmers depend upon animal husbandry for their livelihood.

Storage of food grains

• Crops are seasonal. To provide food grains throughout the year and at every place in the country, theses are kept in storage.
• On domestic level, food grains are stored in small containers made of tin coated iron or mud.
• On commercial scale, foodgrains such as wheat, rice, gram etc., are stored either in gunny bags, or in grain-silos.

Storage of food grains

• Crops are seasonal. To provide food grains throughout the year and at every place in the country, theses are kept in storage.
• On domestic level, food grains are stored in small containers made of tin coated iron or mud.
• On commercial scale, foodgrains such as wheat, rice, gram etc., are stored either in gunny bags, or in grain-silos.

Polyester

• This fibre derived its name from a combination of two commonly known words namely polymer - having many parts and -ester - a chemical compound due to which fruits get their names.
• It is a durable fibre possessing the characteristics of resiliency due to which they are resistant to wrinkles.
• They are also impervious to most chemicals, shrinking, stretching.
• It can be used for the purpose of insulation by developing hollow fibers.

Leveling helps in even distribution and soil is leveled after ploughing. A plank of wood or iron is used for this. Leveling also helps in water distribution without logging during irrigation.

An ideal Fuel is one which possesses the following characteristics:

• It should be readily available.
• It should be inexpensive.
• It should burn easily in air at a judicious rate.
• It should liberate large amount of heat.
• It should leave behind any undesirable residues.
• It should be easy enough to store, transport, and handle.
• It should have high calorific value.

Vaccines are the medicines that prepare the body to fight against a disease without before getting exposed to the disease. When foreign invaders such as bacteria or viruses responsible for that disease enter the body, our immune cells called lymphocytes respond against them by producing antibodies.

The main difference between mineral acid and organic acid is that mineral acids are inorganic compounds composed of different chemical element combinations whereas organic acids are organic compounds essentially composed of carbon and hydrogen atoms 

High rise buildings are massive structures which exert tremendous pressure on the ground and are likely to sink.So to avoid sinking, their foundations are made wide, to decrease the pressure on the ground.

As we know that same force acting on a smaller area exerts a larger pressure but smaller pressure on larger area.

This further explained by the formula below,which shows that force and the area it acts upon are inversely proportional.

• Metals are elements that conduct heat and electricity, and are malleable and ductile. Metals are electropositive elements because they can form positive ions by losing electrons. Non-metals are electronegative elements because they can form negative ions by gaining electrons.
• Non-metals are elements that do not conduct heat and electricity, and are neither malleable nor ductile.