BRITS AND BEYOND – SCIENTIFIC REPORT: “DENSITY OF SOLIDS AND LIQUIDS”

Report by: Alejandro Lázaro (2 nd ESO B)
Lab colleagues: Arturo Blasco (2 nd ESO A) and Jazmín Fermín (2 nd ESO A)

INTRODUCTION

The density is a property that shows the relationship between the mass and the volume of bodies.
For example, iron is denser than cotton, because if you take two pieces of equal size of both
substances, the iron piece will be heavier. Or, if you want to have 1 kg of iron, you will need a
smaller piece than if you want to get 1 kg of cotton.
It is a specific property, which means that each pure substance has its own value. Consequently,
knowing the density of an object is a useful data to identify the substance with which it is formed.
If you write in GOOGLE: “density of water” the value that appears is 997 kg/m 3 . This is almost
1000 kg/m 3 , which means that if we took a cube of water whose dimensions were 1m x 1m x 1m, its
mass would be 1000 kg.
As curious and careful scientists, we decided to put GOOGLE to the test and carry on an
experiment to see if this was true. To make it more interesting, the density of different screws made
with zinc-plated steel (which, according to the internet, is 7140 kg/m 3 ) was also tested.
Zinc-plated steel is a type of steel that is coated with zinc (a metal), to give it resistance to
corrosion. If the screws are all really made with this metal, their density has to be the same, no
matter the number or the size of screws that we take.

USED MATERIALS
For this experiment, we used:

• A scale: to measure the mass of the water and the screws
• A graduated cylinder: to measure the volume of the water and the screwe
• A beaker: to pour the extra water after each test
• A bottle of distilled water: to pour water in a controlled way
• Water and screws (two different sizes)

PROCEDURE

a) WATER: first, we weight the graduated cylinder empty on the scale and we pour some water on
it. Then, we weigh the graduated cylinder but this time with water inside, and we subtract the mass
of the empty graduated cylinder to the weight of the graduated cylinder with water. The value that
we obtain is the mass of the water.
The next step is obtaining the volume of the water. We know this by reading the marks on the
graduated cylinder.
Finally, we obtain the density with the formula (D = m/V). We repeat this process four times to
obtain a more reliable result.

b) SCREWS: first, we weight one screw of each type (big = 14,6 g / small = 2g). With this, we have
the mass of the screws. We choose the ones that we are going to put into the graduated cylinder.
Second, we measure the quantity of water in the graduated cylinder. Then we put the screws. We
subtract the quantity of water to the quantity of water with screws, and we obtain the volume of the
screws*.
Finally, we obtain the density with the formula (D = m/V). We repeat this process four times to
obtain a more reliable result.

• When you need to calculate the volume of an irregular body, where applying a formula is impossible or you can’t measure its dimensions, you can know its volume by introducing them in a known quantity of water and measuring the increase in the level of the water. The increase in the volume of water will be the volume of your body.
  It is important to add that this can be done because there is an equivalence between units of volume and capacity:
  Example: A cube of 1 cm 3 can be filled with 1 mL of water

Finally, we transform, using conversion factors, the results into the International System units:

CONCLUSION

• When you need to calculate the volume of an irregular body, where applying a formula is impossible or
  you can’t measure its dimensions, you can know its volume by introducing them in a known quantity of
  water and measuring the increase in the level of the water. The increase in the volume of water will be
  the volume of your body.
  It is important to add that this can be done because there is an equivalence between units of volume and
  capacity:
  Example: A cube of 1 cm 3 can be filled with 1 mL of water

a) WATER: the result obtained (997,5 kg/m 3 ) is practically the same as the expected (997 kg/m 3 ). If
we look at each measurement separately, the results are not so accurate, but taking into account the
media, we can conclude that the data on the Internet is correct, and that our measurements were
quite precise.
b) SCREWS: the result obtained (6410 kg/m 3 ) is not the same as the expected (7140 kg/m 3 ). In this
case, 3 out of the four measurements are quite similar to the expected value, but one of them is
pretty inaccurate. This can happen because, as the volume of the screw is so small (probably less
than 1 ml) and the graduated cylinder can’t distinguish measurements smaller than 1 ml, so it was
impossible for us to measure that volume in a precise way.

In conclusion, as scientist we can’t take nothing for granted and we have to be very careful with our
job and our measurements to make sure that our experiments have a successful result. Taking notes
and writing down everything we do is also very relevant to track our work and be able to look back
if anything goes wrong.
Remember that science can be tough, but it also can be FUN!

Report by: Alejandro Lázaro (2 nd ESO B)
Lab colleagues: Arturo Blasco (2 nd ESO A) and Jazmín Fermín (2 nd ESO A)