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Ask QuestionPosted by Samiksha Kushwah 7 years, 6 months ago
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Posted by Arpita Kumari 7 years, 6 months ago
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Posted by Arpita Kumari 7 years, 6 months ago
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Meghna Thapar 5 years, 7 months ago
all bearing works on the principle of rolling friction. Ball bearing contains steel balls or rollers. It is used between the wheels and axle of a car to reduce friction. A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.
Posted by Devika Km 7 years, 6 months ago
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Devashish Bajpai 7 years, 6 months ago
Arpita Kumari 7 years, 6 months ago
Sonali Aggarwal 7 years, 6 months ago
A fertilizer is a natural or synthetic, chemical-based substance that is used to enhance plant growth and fertility.
Posted by Subrat Tandan 7 years, 6 months ago
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Divyansh Chauhan 7 years, 6 months ago
Sonali Aggarwal 7 years, 6 months ago
A vaccine is a biological preparation that provides active acquired immunity to a particular disease.
Posted by Mayank Baranwal 7 years, 6 months ago
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Posted by Rudra Pratap Singh 7 years, 6 months ago
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Poorvshree Chaturvedi 7 years, 6 months ago
Posted by Thomas Kj 7 years, 6 months ago
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Posted by Neeru Singla 7 years, 6 months ago
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Sayli Wable 7 years, 6 months ago
Posted by Neeru Singla 7 years, 6 months ago
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Meghna Thapar 5 years, 7 months ago
Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an
infected person or carried through an animal. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.
The communicable diseases can occur and spread in the following ways:
- By breathing of air containing microorganisms.
- By taking infected food and water.
- Through insect bites.
- By sharing infected injection needles.
- By physical contact with an infected person.
For example – common cold disease spreads by breathing air containing microorganisms.
Prevention of communicable diseases: Some of the methods for preventing the occurrence and spreading of communicable diseases are given below:
- A person suffering from common cold should always cover his mouth and nose with a handkerchief while sneezing, so that microorganisms do not get into the air.
- We should keep our food covered to protect it from getting infected by flies. We should also drink clean and safe water.
- We should protect ourselves from mosquito bites by using mosquito nets over our beds while sleeping, by putting fine wire mesh on doors and windows, or by using mosquito repellent creams and devices.
- We should make sure that only disposable syringes and needles are used for giving us injections.
- We should avoid physical contact with an infected person, and not use his towel, clothes or bed.
- Some of the diseases can be prevented by vaccination at proper time.
Posted by Ahsan Ali 7 years, 6 months ago
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Sayli Wable 7 years, 6 months ago
Rudra Pratap Singh 7 years, 6 months ago
Posted by Amit Kumar 7 years, 6 months ago
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Posted by Omkar Mane 7 years, 6 months ago
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Sonali Aggarwal 7 years, 6 months ago
It used to be believed that of the first 92 elements on the periodic table (1 is hydrogen and 92 is uranium) that 90 elements occur naturally.
Posted by Nitish. Alekya. 7 years, 6 months ago
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Trishul Suthar 7 years, 6 months ago
Sanviya Prasad 7 years, 6 months ago
Posted by Khushi Singh 7 years, 6 months ago
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Sonali Aggarwal 7 years, 6 months ago
Yeast used in fermentation.
Acetobacter bacteria converts alcohol into acetic acid.
Posted by Piyush Doshi 7 years, 6 months ago
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Nishu Singh 7 years, 6 months ago
Posted by Suresh Nepolean 5 years, 9 months ago
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Meghna Thapar 5 years, 7 months ago
- Physical Properties of Metals:
- Physical State: All metals are solids at room temperature.
Exceptions: Mercury and gallium are liquids at room temperature.
- Lustre: All metals in their pure state have a shine and can be polished to give a highly reflective surface.
- Malleability: Metals have the ability to withstand high tensile strength and can be made into thin sheets. This property of metals is called malleability.
- Ductility: Metals can also be drawn into thin wires. The ability of metals to be drawn into wires is called ductility. Example: Gold and silver are the most ductile metals.
- Conduction of Heat: Metals are good conductors of heat and have high melting points. Example: Silver and copper are very good conductors of electricity.
Exceptions: Lead and mercury are poor conductors of heat.
- Conduction of Electricity: Metals are good conductors of electricity.
Example: All electric wires are made of copper.
- Hardness: Metals are generally hard, and their hardness varies from metal to metal. Alkali metals such as sodium and potassium are soft metals and can be easily cut with a knife.
- Melting and Boiling Points: Metals usually have high melting and boiling points. Tungsten has the highest melting point whereas sodium and potassium have low melting points.
- Sonorous: Metals which produce a sound on striking a hard surface are said to be sonorous.
Posted by Kashish Gupta 7 years, 6 months ago
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Joan Mariam Jijo 7 years, 6 months ago
Vishwa Savaliya 7 years, 6 months ago
Posted by Murtaza Jawad 7 years, 6 months ago
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Yogita Ingle 7 years, 6 months ago
Techniques to prolong the shelf life of a food are called food preservation. Some common methods of food preservation are as follows:
Sun Drying: This is a traditional method of food preservation. Sun-drying helps in removing moisture from food. Grains are dried in sun before being stored. Many vegetables are also sun-dried so that they can be used in off season.
Chemical Method: Some chemicals prevent the growth of microorganisms in food. These chemicals are used in pickles and jams to preserve them. Salt, acids and oil are also used as food preservatives. Examples: sodium benzoate and sodium metabisulphate.
Preservation by common salt: When a food item is kept in plenty of salt, water from food comes out because of osmosis. It results in dehydration of the food item. Absence of moisture helps to prevent the growth of microbes. Fish, meat and pickles are preserved by adding salt.
Preservation by Sugar: Sugar preserves food by reducing moisture in food. Jam, jelly and squash are preserved by adding sugar.
Preservation by Oil and Vinegar: The layer of oil on top of food prevents oxygen from entering the food. Some microbes do not survive in absence of oxygen. Some microbes cannot survive in acidic environment and thus vinegar is an effective food preservative.
Heat and Cold Treatment: Most of the organisms can survive within a particular range of temperature. When the temperature becomes too low or too high, organisms cannot survive. Heating a food item or freezing a food items thus helps in preservation. In most of the households, milk is boiled twice or thrice in a day to prolong its shelf life. Milk is pasteurized before being packed. Pasteurization involves heating the milk to 70°C for about 15 to 30 minutes and is then quickly cooling down the milk. Pasteurization helps in killing the microbes which may be present in milk.Most of the organisms can survive within a particular range of temperature. When the temperature becomes too low or too high, organisms cannot survive. Heating a food item or freezing a food items thus helps in preservation. In most of the households, milk is boiled twice or thrice in a day to prolong its shelf life. Milk is pasteurized before being packed. Pasteurization involves heating the milk to 70°C for about 15 to 30 minutes and is then quickly cooling down the milk. Pasteurization helps in killing the microbes which may be present in milk.
Storage and Packing: Some food items are stored in air-tight packets so that oxygen is not available for proliferation of microbes. Some food items are packed in cans; along with some preservatives. Oily food; such as potato chips; is packed in air-tight packets which are filled with nitrogen gas. Nitrogen gas prevents the oily food from becoming rancid.
Posted by Murtaza Jawad 7 years, 6 months ago
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Yogita Ingle 7 years, 6 months ago
Advantages of food preservation:
1. Food preservation prevents the food from being spoiled by the action of enzymes and microorganisms.
2. Food preservation increases the safe storage period of foodstuffs.
3. It increases the availability of out of season foodstuffs.
4. It increases the availability of various foodstuffs even at distant and not easily approachable places. In other words, it makes the transportation of the food materials easier.
Posted by Aishwarya Lakshmi 7 years, 6 months ago
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Sonali Aggarwal 7 years, 6 months ago
Chlamydomonas,Spirogyra,Blue green algae,Diatoms and Seaweeds
Posted by Ashwini Choudhary 7 years, 6 months ago
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Vishwa Savaliya 7 years, 6 months ago
Kashish Bhambhani 7 years, 6 months ago
Sonali Aggarwal 7 years, 6 months ago
The process of removing weeds(unwanted plants) from a crop field is called weeding.
Kashish Gupta 7 years, 6 months ago
Posted by Gavnish Kumar 7 years, 6 months ago
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Sayli Wable 7 years, 6 months ago
Kashish Gupta 7 years, 6 months ago
Aishwarya Lakshmi 7 years, 6 months ago
Posted by Prakash Bamaniya 7 years, 6 months ago
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Yogita Ingle 7 years, 6 months ago
Growth of plant is a chemical change because in chemical change new substances will be formed even in a plant growth a seed changes to a seedling and that into a plant or tree and the characters and appearance changes. Growth of plant is a irreversible changes because it’s a permanent changes. It cannot be reversed so it is a irreversible change.
Posted by Yash Bro 7 years, 6 months ago
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Sonali Aggarwal 7 years, 6 months ago
Metal oxides are basic in nature because they form base when dissolved in water.
Posted by Arnab Tripathy 7 years, 6 months ago
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Yogita Ingle 7 years, 6 months ago
Protozoa are one-celled organisms that can cause diseases ranging in severity from mild to deadly. These organisms can be classified as parasitic or free-living.
Parasitic protozoa are found in organisms such as ticks, flies and mosquitoes. Example: Malaria. Malaria is carried by an infected mosquito.
Some protozoa help in the final degradation of waste and sewage while some are symbiotic in nature. Paramecium helps in killing harmful bacteria.
Protozoa play a key role in maintaining the balance of bacterial, algal, and other microbial life. They are also an important food source for larger creatures and the basis of many food chains.
Posted by Angad Gupta 7 years, 6 months ago
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Olibhia Ghosh 7 years, 6 months ago
Posted by Sonali Sahu 7 years, 6 months ago
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Ritesh Raj 7 years, 6 months ago
Posted by Sonali Sahu 7 years, 6 months ago
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Posted by Adarsh Yadav 7 years, 6 months ago
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Sonali Aggarwal 7 years, 6 months ago
Yes that's true because microorganism help in the decomposition of dead plants and animals and in their absence dead organisms would not get decomposed and our earth would become a heap of dead plants and animals .
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Arpita Kumari 7 years, 6 months ago
1Thank You