# Advice 1: How to determine the density of water

Water is one of the key compounds on earth. Many scientists believe that in her life began. It is unique. For example, this is the only fluid that is compressed upon lowering temperature, and this is a very important feature. Some of its properties are anomalous. Values of the heat capacity, surface tension, viscosity striking. One of the interesting features observed in high densities.
You will need
• Handbook of physical quantities, the calculator.
Instruction
1
Thus, all long been no secret that the density of a substance, whether liquid or solid aggregate state can be calculated as mass divided by volume. That is, in order to experimentally determine the density of ordinary liquid water, you need to:1) Take a measuring cylinder, weigh it.
2) Pour water into it, to fix its occupied volume.
3) Weigh the cylinder with water.
4) Calculate the difference of the masses, giving you a lot of water.
5) Calculate the density of the known formula
2
However, scientists noticed that the density values differ at different temperatures. But the most surprising thing, according to what law this change takes place. So far on this phenomenon puzzled scientists around the world. No one can unravel the mystery and answer the question: "Why is the density when heated from 0 to 3.98 increases, and then decreases to 3.98?" A couple of years ago the Japanese physicist, Masakazu Matsumoto suggested a model of the molecular structure of water. According to this theory, creates some polygonal microabrasive - vitrite, which, in turn, dominated by the phenomenon of the lengthening of the hydrogen bonds and shrink the molecules of water. However, this theory is still not confirmed experimentally. A graph of the dependence of density on temperature are presented below. To use it you need to:1) Find the desired temperature value on the corresponding axis.
2) Drop a perpendicular on a graph. Mark the intersection of a line and function.
3) From the resulting points to draw a line parallel to the axis of the temperature on the axis density. The point of intersection is the desired value.Example: Let the temperature of the water 4 degrees, then the densityafter building, is equal to 1 g/cm^3. Both of these values are approximate.
3
To determine a more accurate density values, it is necessary to use a table. If there is no data when the desired temperature value, then: 1) Find the values between which is the desired result. For better understanding, consider the example immediately. Let the desired density of water at a temperature of 65 degrees. It is between 60 and 70.
2) Draw a coordinate plane. Set the axis of abscissa as the temperature, the y-axis as density. Note on the chart of known points (A and B). Connect them direct.
3) Drop a perpendicular from the desired values of temperature on the period obtained above, mark it as point C.
4) Mark the points D, E, F, as shown on the chart.
5) Now clearly shows that the triangles ADB and AFC are similar. Then the relation is valid:
(0,98318-0,97771)/(0,98318-x)=(70-60)/(65-60);
0,00547/(0,98318-x)=2
1,96636-2=0,00547
x=0,980445
Accordingly, the density of water at 65 degrees equals 0,980445 g/cm^3
This method of finding the values is called interpolation.
Note
Pay attention to the dimensions.
Carefully carry out all the calculations. Remember that the data in this table are given for ordinary water. From salt water the density is greater.

# Advice 2: How to determine the density of the liquid

The fluid density is a physical quantity that shows the mass of the fluid per unit volume. The density of the fluid can be measured as an indirect method, and direct measurements with the help of special devices.
You will need
• measuring Cup or beaker, scale, ruler, hydrometer.
Instruction
1
So, you have a liquid the density of which is going to determine. Take the empty measuring Cup or beaker, place it on the scale and determine the mass of the empty vessel with no fluid. Label it m1, for example. Then pour into this vessel the liquid whose density you want to measure. Pour the liquid to such a level that it was easy to determine its volume (in a small measuring cups marked scale of volume in milliliters).
2
After you have determined and recorded the volume of fluid (V), again place the container on the scale, just now it will be liquid. Record the new mass and label it m2. Knowing the mass of the empty dish m1 and complete m2 of the vessel, determine the mass of the liquid m by the formula: m = m2 – m1. Now you can go directly to the definition of the density Rho:

ro = m / V,

where m and V – mass and volume of the fluid found above.
3
Remember that the liquid volume is usually measured in kilograms per cubic meter or in grams per cubic centimeter. Therefore, translating the measured values to one or second standard system of units of measurement. For example:

1 milliliter = 1 cubic centimeter

1000 liters = 1 cubic meter

1 kilogram = 1000 grams
4
If a vessel with the liquid is large enough, but you know the mass of the empty dish, and m1 the mass of the filled vessel m2, it is possible to do the following. First, find the mass of liquid in the vessel by the formula m = m2 – m1. Then use a ruler or measuring tape, measure the geometric dimensions of the vessel: for rectangular vessels measure the height, width and length, for cylindrical – diameter and height. For finding the volume of a rectangular vessel, use the formula:

V = a * b * h

where a is width, b – length, h – height of the vessel.
5
To find the volume of the cylindrical vessel, take the following formula:

V = (pi * d * d * h) / 4,

where pi is the number PI = 3.14, d is the vessel diameter, h is its height (the height of the liquid level).

After finding volume find the density of the liquid, as in the previous case, by the formula Rho = m / V.
6
The problem of determining the density is much easier if you have a hydrometer. This device is a glass tube with float and scale. Just dip it in the liquid so that it does not touch the bottom, and on a scale at the top of the hydrometer will see the density of the liquid. Often motorists use hydrometer to determine the density of the electrolyte in the battery.
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