As before, it relies on the powers of ten idea to reduce many of the zeros. There are just too many of them! However, there is a notation that minimises the risk of making mistakes when working with such numbers. Roughly 10 20 of these molecules would be needed to make a single raindrop.Īs when writing very large numbers, there is an inherent danger in writing very small numbers such as 0.0. It is difficult to comprehend a number this small, but you can probably imagine why it is impossible to do the halving experiment with a molecule. However, if its shape were likened to a tiny sphere, it would be about 0.0 m across. It is not easy to describe the size of a water molecule because its shape is not regular. Molecules are the basic particles of many solids, liquids and gases. This smallest particle that is still water is called a water molecule and its dimensions are almost inconceivably small. The 68th division by two, like the halving of a single cow, would destroy the water. In principle, a typical raindrop - say, 2 mm across - could be halved in volume 67 times before a single particle that is still recognisably water emerges. It is a process that cannot be studied with the naked eye - or even with a conventional microscope. Unfortunately, once a drop of water is halved several times, it becomes extremely small. Higher in the sky where it is colder than at the land surface, invisible water vapor condenses into tiny liquid water dropletsclouds. You can conclude that one whole living cow is the smallest item from which herds of any size can be composed. Overview Science Multimedia The air is full of water, even if you can't see it. If this remaining cow were halved, you would agree that what remains is certainly not a living, whole cow. An average of two to three TCs make landfall in southern China each year. Southern China is the most TC-prone area within China. Repeating the process gives two cows and repeating it again leaves one living cow. Introduction Tropical cyclones (TCs) usually bring heavy precipitation, strong winds, lightning strikes, and storm surge, which cause economic loss and endanger human security. If you halve the herd, you get four cows. One analogy for this 'halving' of a drop of water is to define a single living cow starting from a small herd of eight cows. In other words, if you start with a raindrop and keep halving its volume, is there a point when a further reduction gives something that stops being water? It is often useful in science, when dealing with complex ideas, to think of an analogy. It is interesting to contemplate whether there is such a thing as a smallest particle that is still recognisably water and from which all larger volumes of water are made. Even these drops are small, but clearly they are water. Imagine dividing the gap between adjacent millimetre marks on a ruler into 100 parts! Many of these droplets coalesce to give a raindrop that is about two-thousandths of a metre wide ( m, 0.002 m or 2 mm). This corresponds to mm or 0.01 mm, which is very small. The typical distance across a water droplet in a cloud is one hundred-thousandth of a metre, that is, m or 0.000 01m.
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