• Have you ever seen a normal distribution curve? It's a sort of sombrero shaped curve which shows the probability of something having a particular random value. It's tallest near the center and thin out by the sides. For instance, the height of 30 year old men, follows a normal distribution curve. Most men are near the average, but some are much higher, and some are much smaller. So it is with the (square of the) speed of individual molecules. So a glass of water at 10 degrees C really has most molecules around 9-11 degrees C, but some are much lower and some much higher. There are always a few molecules near the surface that have enough energy to leave the liquid altogether. As the average temperature increases, more and more molecules evaporate, until when you get to 100 degrees C a strange effect happens: the average temperature stays at 100 for a quite a while because the molecules hotter than 100 leave altogether, so the average temperature of the remaining liquid stays the same until it's all gone.
  • What I gathered from your question is that if water boils at 100 deg cel then why the same water evaporates at room temperature.. If this is what you intend to ask then this answer is for you. 01)The air around the surface of the water at room temperature is in unsatuarted state.That means air still has the capacity to carry or accept the air molecule.(on a particular day we say that today humidity is less or more, humidity is the measure to express the water carrying capacity of the air on a particular day depending upon the climatic condition of that day) 02)So water molecule will leave the water & go into the air to make the air saturate with water.(but it can not do because the quantity of air with respect to water in pan or glass is much much high, more over air moves away.) 03)Since the water molecule went into the air obviously it needed some energy to accomplish the task... It used heat of vaporisation. 04) On a rainy day the humidity is more that mean air has more water in it,on such days rate of evaporation is less.
  • When water boils, the bottom water (or water molecules)touching the hot surface of the pan gets excited first and turns into a gas; hence, you see the bubbles(gas)trying to run up to the surface and escape into the atmosphere. Molecules in a liquid move faster as it gets hotter. It doesn't need to reach boiling point to become a gas. In a puddle for instance, the water molecules on the surface just need to get hot enough to get excited, move faster, spread apart and separate from the other water molecules and into the air. Picture a penguin huddle. They stick together on a very cold day. However, as the temperature gets warmer, the outside penguins are free to move and seperate from the group.

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