Do you want to calculate the density of water? Don’t know how to do it or just find it complicated? Do you have an exam and you have not understood well how the density of water is calculated? Don’t worry, calculating the density of water is very simple, and here we will explain step by step how to do it.
To begin, we must know what is meant by density, in order to know what we are calculating and what its meaning is, as well as what these data are used for.
Density tells us the amount of mass that a certain object or liquid has in a given volume. And its generic formula is density=mass / volume, that is, d=m/v
Next we are going to use some calculations and the main formula for density to show you how to calculate the density of water .
Calculate the density of water
To begin we are going to prepare the materials that we will need. Among them we find a cylinder or a graduated cylinder. These containers are special for measuring the exact volume of liquids, since they come with lines that indicate the measurements. Next we proceed to calculate the mass and volume of the water, since they are the data we need to calculate the density formula.
In the cylinder or the test tube we are going to add the amount of water from which we are going to make the density calculation, therefore, to have the exact value we will have to measure only the mass of the water, removing what the cylinder weighs. So we’re going to start by first weighing the cylinder on the scale. Start by turning on the scale and making sure it is set correctly by marking zero.
Then put the empty measuring cylinder on the scale, write down on a piece of paper the mass of the cylinder that comes out on the scale. Remember to record the data measured in grams. Now we will add the water to the cylinder, it really does not matter that much how much water you add, just that you write down the exact amount. To do this, you must bend down until the cylinder is at the height of your face, and your eyes must be at the height of the water line. You should look at the bottom of the meniscus, which is the curve that water makes when we see it at eye level. This data tells us the volume that the water occupies, the other data that we need to calculate the density of the water, so it is important that it is exact so that our calculations are correct. The volume will be indicated in millimeters.
Once we have taken note of the volume, we will place the test tube or cylinder on the scale, turning it back on first and checking that it is well adjusted and completely at zero. Take note of the exact weight that the scale marks, but remember that it must be in grams. Next we will proceed to calculate the exact mass of water alone, for this we take the weight of the water in the level test tube and subtract the weight of the empty test tube that you calculated at the beginning of everything.
Remember that if in the course of moving and weighing after noting the volume you have spilled some water from the cylinder, then you will have to re-observe and write down the exact new volume. Now that we have all the data we need, we just have to find the main formula and substitute the values with our data. The main formula is: d (density)= m (mass)/ v (volume).
Example
For example, imagine that these are the data obtained following the previous steps:
– mass of empty test tube= 10g
– mass of test tube with water= 17g
– mass of water= 17-10=7g
– volume of water= 6.5ml
The density of the water will be:
d= 7/6.5= 1.077g/ml
Calculate Density From Water Displacement
This technique is used to calculate the density of an insoluble and irregular solid. For this we will need to follow some of the steps of calculating the density of water, but in this case we are not going to weigh the empty test tube, but we will directly weigh the test tube with a certain amount of water on the scale that allows us to later add the object without problems.
We write down the exact weight that the perfectly calibrated scale will dictate, and then we will also write down the volume by looking at the line that marks the water in the test tube.
Once we have these data ready, we will add the object being careful that no water comes out, because if this happens we must start again and also dry the object to be measured very well. We can skip this step and weigh it directly on the scale if the shape and composition of the object allows it, which is normal and faster.
Then we write down the data as in the first step, noting the volume and mass.
To have the exact data of the mass and volume of the object that interests us, we will make the difference of values between those obtained with the object inside the water and those obtained only from water. With these exact and accurate data we will only have to use the general formula of density and carry out its calculation.
If , for example, these were the data obtained, we would calculate the density as follows:
– Initial volume of test tube and water: 6 ml
– Initial mass of heavy object: 4g
– Final volume of test tube, water and object: 8ml
We calculate the volume of the liquid:
v= 8- 6= 2ml
We calculate the density:
d= 4/2= 2 g/ml
Variations in water density
Water does not always have the same density, especially if it is pure, since this will depend on some factors, for example temperature, although it is usually always around 1g/ml, but in science it is very important to know the exact measurements of each variable that we use, that is why the density of the water is always measured in each case and the generic value of 1g/ml is not taken. Normally, the colder the pure water is, its density will be higher. If for example the water is at 0°C then the density of the water could be 0.998g/ml, while the density of the water at a temperature of about 80°C could be 0.9721g/ml. Perhaps at first glance for you it is not a big difference, only a few tenths, but in laboratories, scientific research and in experiments, for example, they can make a big difference in the calculations and results.
What is the use of knowing density?
We have already given you the definition of density, but for practical purposes, density tells us how much a certain object weighs in a designated space. With this data we can compare various materials and choose the one that best suits us. Also, if a density is given to us, but we don’t know exactly what material it corresponds to, we could get an idea thanks to some lists where the densities of many elements are collected. Remember that it is very important that we write down the exact measurements and in the correct metric unit, the mass will always be in grams and the volume in milliliters. Surely with this explanation you now know how to calculate the density of water, so get to work and get to it!
What do you need to calculate the density of water?
- Graduated cylinder or test tube
- A balance
- Water
- Calculator (optional)