Density, Definition, How We Calculate It, Examples, What Affects It And How (Lab Report Sample)

Lab Report for the Density Lab
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1.Density is calculated by dividing the mass of a specific object with its volume. It is a property which characterizes each substance. The mass of atoms, their size, and how they are positioned are related to the density of a substance. Its SI unit is kg/m³. Objects which have the same volume but different mass also have different densities. Mass (m) is the quantity of matter in an object and stays the same regardless of the place or circumstances. The SI unit of mass is the kilogram (kg). It is measured with the aid of a scale. Volume is the amount of space occupied by an object in the three dimensions and it is quantified using the SI unit called the cubic meter (m³). It is measured in a different way for liquids and solids. The density is given by the following equation.
D=mass / volume or D= m / V
In the case of a rectangular prism like a brick, for instance, there are 3 dimensions that need to be measured first and they are shown below. These are the prism’s length, width and height. They will be measured with the help of a ruler or a measuring tape. This depends on the size of the object. After the dimensions are measured in meters (m), the volume can be calculated by multiplying the three dimensions mentioned above. The volume will be in m³. The mass can be easily found with the aid of a scale and will be put in kilograms. Then from the above equation, the density is calculated in m³/kg.
As an example, there is the simple exercise below, where the density will be calculated with specific numbers. There are 3 rectangular prisms which have been weighed with the help of a scale and their mass has been written down in kilograms. Their length, width and height have been measured with the aid of a measuring tape and have been written down in meters. In order to calculate their volume, we have to multiply their 3 dimensions.
For the green prism, we have V=0.2m*0.2m*0.3m=0.012m³
d=m/V=24kg/0.012 m³=2000kg/ m³
For the yellow prism, we have V= 0.1*0.1*0.4=0.004 m³
d=m/V=77.2kg/0,004 m³=19300kg/ m³
And for the brown prism, we have V=0.2*0.4*0.6=0.048 m³
d=m/V=14.4/0.048= 3000kg/ m³
If our prism is smaller, the units of its mass and dimensions could be in grams and meters, respectively. In that case, we can have the following example.
The mass is again found with the help of a scale. However, since now it is a much smaller object than before, an electronic scale of high accuracy must be used. The mass is found to be 200g. The dimensions are measured with the help of either a measuring tape or a ruler. A ruler can be easily used due to the small size of the object. For the volume, we multiply the height, length and width. Volume of cuboid = Length × Width × Height = 6 × 4 × 5 = 120 cm³. Then, the density is easily calculated. Density = Mass/Volume = 200/120 = 1.67 g/cm³. This can be converted to the units of SI, but it is better to stay as it is, due to the great number of decimals.
3. When we change the temperature of a substance, its volume changes too. It may expand or contract. The vast majority of materials grow in volume if we raise their temperature, while the opposite happens if their temperature drops. This phenomenon is called thermal expansion and thermal contraction, respectively. Thermal expansion happens when an object becomes larger due to an increase in the object's temperature. This is because temperature affects the energy of its molecules. If their energy increases, their movement increases, too. A higher temperature means that the molecules move with a higher speed and more freely than before. As a result, they move further apart from each other so the object expands. As a consequence, the volume of the object will increase. The opposite happens when we remove heat from a material. The amount of matter, however, stays the same.
Molecules are not affected by changes in temperature. Their size and number stay the same. They just move closer or apart from each other. That is the mechanism that causes an object to expand or contract if the temperature rises or drops respectively. Water, for instance, can be found in three states. It is liquid in its state at about 20 degrees Celsius. When water is heated, its molecules move in a more free way. When the temperature gets to the boiling point for water (100 degrees Celsius), it changes its liquid state and begins to evaporate. Every liquid has a different boiling point. Gases have molecules that move even more freely and can expand so much that can even expand to cover a whole room. It should be mentioned that the particles in solids cannot leave their fixed places as they have stronger bonds between them, so solids do not show a great change of their volume if the temperature is ...