For example, water left in a bowl will slowly disappear. The water evaporates into water vapor, the gas phase of water. The water vapor mixes with the air.
The opposite of evaporation is condensation.
When the molecules in a liquid are heated, they move faster. This makes them full of energy and so the particles collide with each other, and eventually they become so far apart that they become a gas.
During evaporation only the molecules near the liquid surface are changing from liquid to vapor. During boiling the molecules inside the volume of the liquid are also changing to vapor. For this reason during evaporation no bubbles are formed, instead they are formed during boiling.
Evaporation can happen at any temperature, while boiling happens only at a specified temperature called the "boiling point". Evaporation happens slowly, but boiling happens quickly.
Some liquids evaporate more quickly than others. There are many factors that affect the evaporation rate.
The rate of evaporation depends on the liquid's exposed surface area (faster when increased), the humidity of surroundings (slower when increased), the presence of wind (faster when increased) and the temperature (faster when increased).
Liquid with high boiling points (those that boil at very high temperatures) tend to evaporate more slowly than those with lower boiling temperatures.
Evaporation is a very essential part of the water cycle.
Contract
A contract is an agreement or promise that the law can enforce. The law will enforce some agreements but not others. For example, in most places, if a parent promises to take a child to get ice cream, the law will not enforce that promise as a legal contract.
The legal rules about which promises are enforced by the law can be different in different places (or jurisdictions), but a contract is usually enforced only if it is made by people or groups who want it to be enforced and who know what they are doing.
Sometimes, a contract is written down and signed by the people agreeing to it, but it does not always need to be. People usually sign a contract when something important or costly is being done. For example, when people take a job, they will sometimes sign a contract with their employers. The contract will show what the person must do as part of his job, how much they will be paid, and so on. The person and the employer will sign the contract, and it will become a legal promise.
If someone breaks a contract, another person might sue him or her. In a lawsuit about a contract, the court will look at the contract, listen to what the people who made the contract say about it, and then make a decision about what the contract means.
Face
The face is a part of the body at the front of the head.
It is the part of us that others interact with. On the face are organs of sight, smell, hearing. Especially in a four-legged animal, the face is the part which goes first into the world, and that is why the sense organs and the mouth are there.
In humans, the face includes the hair, forehead, eyebrow, eyelash, eyes, nose, ears, cheeks, mouth, lips, teeth, skin, and chin.
Kolkata
Kolkata (spelled Calcutta before 1 January 2001) is the capital city of the Indian state of West Bengal. It is the second largest city in India after Mumbai. It is on the east bank of the River Hooghly. When it is called Calcutta, it includes the suburbs. This makes it the third largest city of India. This also makes it the world's 8th largest metropolitan area as defined by the United Nations. Kolkata served as the capital of India during the British Raj until 1911. Kolkata was once the center of industry and education. However, it has witnessed political violence and economic problems since 1954. Since 2000, Kolkata has grown due to economic growth. Like other metropolitan cities in India, Kolkata struggles with poverty, pollution and traffic congestion.
The discovery of the nearby Chandraketugarh, an archaeological site has proved that people have lived there for over two millennia. The history of Kolkata begins when the English East India Company arrived in 1690. Job Charnock, an administrator with the Company is traditionally known as the founder of this city. However some academics say that Charnock is not the city's founder.
At that time Kolkata, ruled by the Nawab of Bengal Siraj-Ud-Daulah, had three villages. They were Kalikata, Govindapur and Sutanuti. The British in the late 17th century wanted to build a fort near Govindapur. This was to become more powerful than Dutch, the Portuguese, and the French. In 1702, the British completed the construction of old Fort William, which was used to station its troops and as a regional base. Calcutta was declared a Presidency City, and later became the headquarters of the Bengal Presidency. When regular fights with French forces started, in 1756 the British began to upgrade their fortifications. When this was protested, the Nawab of Bengal Siraj-Ud-Daulah attacked and captured Fort William. This led to the infamous Black Hole incident. A force of Company sepoys and British troops led by Robert Clive recaptured the city the next year. Calcutta became the capital of British India in 1772. However, the capital shifted to the hilly town of Shimla during the summer months every year, starting from the year 1864. Richard Wellesley, the Governor General between 1797–1805, helped in the growth of the city and its public architecture. This led to the description of Calcutta as "The City of Palaces". The city was a centre of the British East India Company's opium trade during the 18th and 19th century; locally produced opium was sold at auction in Kolkata, to be shipped to China.
Pencil
A pencil is a kind of writing equipment that is also used to draw, usually on paper. Most pencil cores are made of graphite powder mixed with a clay binder. So, a pencil is usually made with a piece of graphite mixed with clay that has a wood case around it. The shape is usually a hexagonal prism but some pencils are square or cylinder.
Colored pencils are a kind that do not use greyish silver graphite. Instead, the core is colorful. Colored pencils or crayons are usually meant for drawing rather than writing.
The important difference between pens and pencils is that the tip of a pencil is made of solid graphite (or other material) which is rubbed off onto the paper. A pen has a tip, usually made of metal, with liquid ink coming out and onto the paper. Writing with a pen can smudge when it is still wet. Writing from a pencil can be erased, but writing from a pen usually cannot, unless it uses a special type of ink and eraser.
An early writing tool was the reed pen used by ancient Egyptians, who wrote with ink on sheets of papyrus paper.
Another early writing instrument was the stylus, which was a thin metal stick, often made from lead. It was used for scratching onto black wax that covered white wood, a method used by the Romans. The word "pencil" comes from the Latin word which means "little tail". It is an invention of the 16th century in England.
Some time before 1565 (it may have been as early as 1500), an enormous deposit of graphite was discovered in Borrowdale, Cumbria. The locals found that it was very useful for marking sheep. This particular deposit of graphite was extremely pure and solid, and it could easily be sawn into sticks. This is still the only large scale deposit of graphite ever found in this solid form. Chemistry was in its infancy and the substance was thought to be a form of lead. Consequently, it was called "plumbago" (Latin for "lead ore"). The black core of pencils is still referred to as "lead", even though it never contained the element lead.