In response to the usual question "How much does a liter of water weigh?" most people will offer a glimpse into the directory or simply say: "One kilogram." And in fact, at a temperature of 40 0 C and under conditions of normal atmospheric pressure, the weight of one liter
distilled, that is, devoid of any impurities, water is exactly 1 kg. And who will be able to unequivocally answer the questions "How much does a liter of water from a salt source weigh?" or "Which water is heavier - hot or cold?"
In order not to get into trouble, you need to familiarize yourself with some elementary laws of physics. For more specifics, we should immediately make a reservation that in our article we will not talk about the weight of water, but about its mass. The difference between these terms is that mass is a fundamental indicator of the quantity of a substance, and it is measured in kilograms, and weight is a quantity showing how hard a body with a certain mass presses onto a surface; the unit of measure is Newton.
To answer the question of how much 1 liter of water weighs, first we look at what indicators body weight is made up of. From the course of physics we know that mass is a product
density of matter by the coefficient of acceleration of gravity, which is approximately the same on the entire surface of our planet and is equal to 9.81 kg / m
2 . Fluctuations in these two quantities give us the difference in the mass of the same substance under different conditions.
First, let's talk about fluid density. As mentioned above, the density of pure water under normal conditions is 1000 g / m 3 . If you add impurities, for example, salt, to it, the density will increase, and the water will become heavier. As for the dependence of the mass of the object on temperature, the whole point here is the property of substances to expand when heated. This means that the distance between the molecules becomes larger, and their total number per unit volume decreases, therefore, the substance becomes lighter. However, water has a unique property - it expands not only when heated, but also when cooled (it is because of this that water pipes burst in the winter). Water has the highest density at freezing point; at the slightest deviations of the thermal scale, it becomes lighter. How much a liter of water weighs at various temperatures, if desired, can be found in the directory.
Atmospheric pressure does not affect fluid mass fluctuations as much as
temperature, and the result of its action is opposite to the action of high temperatures. At high pressure, the distance between the molecules decreases, therefore, a larger amount of substance will enter the same volume. As a result, an increase in mass occurs. This can be easily verified in practice by weighing a can of
compressed air and the same can with air under normal pressure.
By the way, do you know how much a liter of water weighs at the pole? 0.5 percent more than at the equator. This phenomenon is due to the rotation of the Earth around its axis. Because of it, centrifugal acceleration increases as one approaches the equator and, consequently, gravitational acceleration increases .
Arguing in this way, it is possible to calculate how much a liter of any liquid weighs, and how this indicator will change depending on environmental conditions.