DENSITY

DENSITY

           The things found around us consist of various shapes of matters. Matter is defined as everything which has mass, occupies space, and is convertible to energy. All matter has physical properties. One physical property of matter is density. Do you know “What is density?”

 

All matter has two properties – mass and volume.

Ø    Mass (m) is the amount of matter (particles) contained in an object.

SI unit of mass = kilogram (Kg)

Ø    Volume (V) is the amount of space occupied by an object.

          SI unit of volume = m³

      Remember this conversion :

          1 liter = 1 dm³          or                1 mL = 1 cm³ = 1 cc

 

So,

Density is one of physical property of matter. Density relates the mass of something to how much space it takes up, which is its volume.

Density is the result of mass per unit volume of matter or substance, the formula :

 

SI unit of density = kg/m³

Remember this conversion :

1 kg/m³ = 10^-3 g/cm³     or          1 g/cm³ = 10³ kg/m³

in Indonesian, I would define the density of the following :

Kerapatan materi di dalam suatu benda yang menjadi ciri khas dari benda itu sendiri.

Ø   Substances of the same type have the same density.

      The density of a substance does not depend on the mass, the volume, or 

    the shape of substance, but it depends on the type of the substance 
   itself.

How to measure the density of an object ?

Given            : Mass            = 4 gram

                          Volume      = 10 cm³

Unknown    : Density (D) ?

Solution       :

D = m/V

      = 4/10 = 0.4 g/cm³ = 400 kg/m³

Question 1 :

I have two objects with the same volume. Both of these objects are iron and wood. Which object has the greatest mass ? Explain!!

Answer :

The biggest mass of iron because iron has a density of particles larger than the wood.

If the same volume then mass of iron is greater because the amount of iron particles more.

Theoretically, the number of particles in the tens of millions (10²³). But to simplify, we assume there are 16 number of particles of iron and wood 6 (for the same volume). Look at the figure below :

Question 2 :

I have two objects with the same mass. Both of these objects are iron and wood. Which object has the greatest volume ? Explain!!

Answer :

For the same mass, the number of particles of iron and wood should be the same. We assume the number of particles of iron and wood is 16.

We know that for the same amount of volume more iron particles. So, if their have the same number of particles, then the wood must increase the volume to accommodate the same number of particles. Look at the figure below:

 

Question 3 :

I have a liquid that is oil, when I pour the oil into different containers and different volume sizes. Where the density of the largest ?

Because the type of a liquids used is same, though mass and volume is different, density will remain the same.

 

Question 4 :

I have a liquid that is water, when I pour the oil into different containers and different mass sizes. Where the density of the largest ?

 

Because the type of a liquids used is same, though mass and volume is different, density will remain the same.

Question 5 :

When water and oil are mixed in one container, why the position is above the oil?

Because the density of oil smaller than water.

Question 6 :

I have three different forms of copper. Which shape has the greatest density?

BRASS

 

Because the type of a solids used is same, though mass and volume is different, the density will remain the same.  Although there are differences in the density values when experiment, their value can still be assumed the same due to differences in the accuracy of different measuring instruments.

Concluded that the density of the brass in the calculation of the laboratory of {(8.37 + 8.70)/2} 8.53 g/cm³, while theoretically of 8.4 g/cm³.

 

Question 7 :

From questions 3, 4, and 6, we can conclude that

a.   Substances of the same type have the same density. 

b. The density of a substance does not depend on the mass, the volume, or the shape of substance, but it depends on the type of the substance itself.

Question 8 :

Observe the following video, CHECK IT OUT

Three identical eggs put in different containers so as to produce conditions such as the picture above. Which liquid has the greatest density? Explain!

 So, the density of a liquid is greatest when the position of the object on top liquid surface or float.

BIBLIOGRAPHY
Sumarwan, dkk. 2010. SCIENCE for Junior High School Grade VII  1^st Semester. Jakarta : Erlangga
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